\documentclass[manuscript=article]{tmr-tex}

% ===== 期刊信息 =====
\journalname{Traditional Medicine Research}
\doi{10.xxxx/tmr.2025.12345}
\year{2025}
\volume{10}
\no{2}
\page{100--120}
\journalweb{https://www.tmr-journal.com}

% ===== 作者信息 =====
\author{Gaofei Yan}
\affiliation[Henan Univ. CM]{Department of Orthopaedics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou 450000, China}
\alsoaffiliation{The First Clinical Medical College, Henan University of Chinese Medicine, Zhengzhou 450046, China}
\email{lihuiying39@163.com}

\author{Peng Yu}
\affiliation[Henan Univ. CM]{Department of Orthopaedics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou 450000, China}

\author{Xianzhong Bu}
\affiliation[Henan Univ. CM]{Department of Orthopaedics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou 450000, China}

\author{Zhengguo Wang}
\affiliation[Henan Univ. CM]{Department of Orthopaedics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou 450000, China}
\alsoaffiliation{The First Clinical Medical College, Henan University of Chinese Medicine, Zhengzhou 450046, China}

\Correspondence{Department of Orthopaedics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou 450000, China, E-mail: lihuiying39@163.com}
\Executiveeditor{Dr. Editor Name}
\keywords{Fangji Huangqi Decoction; Chemical constituents; Pharmacological effects; Clinical application; Quality markers (Q-Markers)}
\tmrabstract{Fangji Huangqi Decoction was first recorded in the classic text Jinkui Yaolüe by Zhang Zhongjing in the Eastern Han Dynasty. The formula is composed of six herbs: Fangji (Stephania tetrandra), Huangqi (Astragalus membranaceus), Baizhu (Atractylodes macrocephala), Gancao (Glycyrrhiza uralensis), fresh ginger, and jujube. It is a representative prescription for "wind–water" syndrome caused by exterior deficiency and excess dampness. Traditionally, it is used to tonify Qi, dispel wind, strengthen the spleen, and promote urination. Modern studies show that this decoction contains a wide range of chemical components, including bisbenzylisoquinoline alkaloids, triterpenoid saponins, flavonoids, sesquiterpene lactones, and polysaccharides. Pharmacological research has confirmed that it can regulate body fluid metabolism, reduce inflammation and pain, improve ventricular remodeling, protect against renal fibrosis, inhibit tumor growth, and regulate glucose and lipid metabolism. Clinically, it has been widely used for nephrotic syndrome, chronic heart failure, rheumatoid arthritis, obesity, and postoperative edema, with clear therapeutic benefits. To improve the quality control system for this classical formula, this paper reviews recent research on its chemical components, pharmacological actions, and clinical applications. Based on the "five principles" of quality markers (Q-Markers) for traditional Chinese medicine—transmissibility and traceability, specificity, efficacy, compatibility in the formula, and measurability—we carry out a comprehensive prediction of potential Q-Markers covering all six herbs. As a result, ten compounds are identified as core candidate Q-Markers: tetrandrine, fangchinoline, astragaloside IV, calycosin-7-O-β-D-glucoside, atractylenolide I, atractylenolide III, glycyrrhizic acid, liquiritin, 6-gingerol, and cyclic adenosine monophosphate (cAMP). These findings provide a basis for the secondary development of Fangji Huangqi Decoction and for establishing a more complete quality control system.}

\begin{document}

\section{Introduction}
Fangji Huangqi Decoction was first described in \textit{Jinkui Yaolüe} $\cdot$ Water Qi Syndrome and Pulse Patterns, Chapter Fourteen, where it is stated: ``For wind–water syndrome with floating pulse, heavy body, spontaneous sweating and aversion to wind, Fangji Huangqi Decoction is indicated.'' The original prescription includes Fangji, Huangqi, Baizhu, and honey-fried Gancao, and is decocted with fresh ginger and jujube. In traditional Chinese medicine (TCM), Fangji is bitter and cold, and is used to dispel wind, remove dampness, and relieve edema. Huangqi is sweet and warm; it tonifies Qi, consolidates the exterior, and promotes water circulation. Used together, they act as the chief herbs, combining elimination of pathogenic factors with support of healthy Qi. Baizhu strengthens the spleen and dries dampness, assisting Huangqi in tonifying Qi and Fangji in transporting and transforming fluids. Gancao harmonizes the other herbs and also supports the spleen. Fresh ginger and jujube harmonize the nutritive and defensive Qi and protect the middle Jiao\cite{ref1}. Overall, the formula is considered a typical prescription for exterior deficiency with internal dampness, with functions of tonifying Qi, dispelling wind, strengthening the spleen, and promoting urination.

With changes in modern medical concepts, Fangji Huangqi Decoction and its modified forms have been applied to a variety of diseases including nephrotic syndrome, glomerulonephritis, diabetic nephropathy, chronic heart failure, rheumatoid arthritis, obesity, liver cirrhosis with ascites, breast cancer-related lymphedema, and postoperative edema\cite{ref1,ref2}. These applications reflect the TCM principle of ``treating different diseases with the same method'' based on pattern identification. At the same time, the modernization of TCM has highlighted the need for scientific quality control systems that can link the complex material basis of formulas with their clinical effects.

The concept of quality markers (Q-Markers), proposed by Liu Changxiao and colleagues, defines a TCM Q-Marker as a component that: 1) can be traced from the raw herb, through processing and preparation, to the body (transmissibility and traceability); 2) is characteristic for a given herb and helps distinguish it from adulterants (specificity); 3) is clearly related to the main therapeutic effects (efficacy); 4) remains meaningful and stable in the multi-herb compatibility environment (compatibility); and 5) can be accurately measured by modern analytical methods (measurability)\cite{ref2}. Although several studies have reported the chemical composition, pharmacology, and clinical use of Fangji Huangqi Decoction, few have tried to build a Q-Marker system that covers all six herbs and connects the material basis to traditional functions and modern indications. In particular, quality indicators for assistant and envoy herbs such as ginger and jujube are often neglected. This limits the establishment of comprehensive quality standards and the further development of standardized products.

The present review aims to: (1) summarize current knowledge on the chemical constituents and pharmacological effects of Fangji Huangqi Decoction; (2) review its major clinical applications; and (3) apply the five Q-Marker principles to predict potential Q-Markers for all six herbs in the formula, and propose a preliminary multi-component quality control scheme.

\section{Materials and methods}
The present work is a narrative review with structured analysis. We searched CNKI, Wanfang, VIP, PubMed, and Web of Science for literature using the keywords ``Fangji Huangqi Decoction'', ``Fangji Huangqi Tang'', ``Stephania tetrandra'', ``Astragalus membranaceus'', ``Atractylodes macrocephala'', ``Glycyrrhiza uralensis'', ``Zingiber officinale'', ``Ziziphus jujuba'', ``chemical constituents'', ``pharmacology'', ``clinical study'', and ``quality marker''. Inclusion criteria were: original research articles or systematic reviews related to Fangji Huangqi Decoction or its core herbs; studies involving chemical analysis, pharmacology, pharmacokinetics, or clinical application; publications in Chinese or English with clear methods and results. We excluded reports with unclear formula composition, obvious duplication, or serious methodological problems.

For Q-Marker analysis, we also consulted the 2020 and 2025 editions of the \textit{Pharmacopoeia of the People's Republic of China} and key papers on Q-Marker theory and on classical formulas with established Q-Marker systems\cite{ref2,ref3,ref4}. Data extraction focused on: main chemical groups and representative compounds, pharmacological targets and pathways, clinical indications and outcomes, pharmacokinetic characteristics, and established analytical methods. These data were then integrated into the five-principle Q-Marker framework for Fangji Huangqi Decoction.

\section{Chemical basis of Fangji Huangqi Decoction}
The material basis of Fangji Huangqi Decoction is the carrier for its multiple pharmacological effects. Modern phytochemistry and analytical chemistry have identified the main active constituents of the key herbs in this formula.

Fangji (\textit{Stephania tetrandra} Radix) is the dried root of a Menispermaceae plant and is the core herb for dispelling wind-dampness and promoting diuresis in this prescription. Its main active constituents are bisbenzylisoquinoline alkaloids, such as tetrandrine (also known as Han-Fangji A) and fangchinoline (Han-Fangji B). These two alkaloids have similar structures and differ only at the C-7 substituent (a methoxy group in tetrandrine and a phenolic hydroxyl group in fangchinoline)\cite{ref3,ref4}. Fangji also contains cyclanoline (Han-Fangji C), dimethyl-tetrandrine\cite{ref5}, aporphine-type alkaloids, and small amounts of flavonoids\cite{ref6}. Together, these alkaloids form the main chemical basis for the ``dispelling wind and promoting urination'' effect of Fangji. It is important to strictly distinguish Menispermaceae Fangji (\textit{Stephania tetrandra}, usually called ``Fen Fangji'') from Aristolochiaceae ``Guang Fangji'' (\textit{Aristolochia fangchi}). The latter contains aristolochic acids with strong nephrotoxicity and has been banned from clinical use.

Huangqi (\textit{Astragali Radix}) is the dried root of \textit{Astragalus membranaceus} (Fisch.) Bge. or related species in the Fabaceae family. It is known as a ``superior Qi-tonifying herb'' and acts as the sovereign herb for strengthening Qi and consolidating the exterior in this formula. Its chemical composition is complex and includes saponins, flavonoids, polysaccharides, amino acids, and trace elements. Among the saponins, astragaloside IV is the most representative, and other astragalosides such as astragaloside I, II, III and related derivatives have also been reported. Most of these saponins are cycloartane-type triterpenoid saponins and are regarded as key substances for the immunomodulatory and organ-protective effects of Huangqi\cite{ref7}. The flavonoids are mainly isoflavones and their glycosides, including calycosin, calycosin-7-O-β-D-glucoside, formononetin, and ononin\cite{ref8,ref9}. Astragalus polysaccharides (APS) are abundant macromolecular components with complex monosaccharide composition and marked immune-enhancing activity\cite{ref10}.

Baizhu (\textit{Atractylodis Macrocephalae Rhizoma}) is the dried rhizome of \textit{Atractylodes macrocephala} Koidz. in the Asteraceae family. Its main active substances are sesquiterpene lactones, volatile oils, and polysaccharides. Atractylone is a characteristic volatile component of Baizhu, but it is easily oxidized or lost during storage and decoction. In contrast, sesquiterpene lactones such as atractylenolide I, atractylenolide II, and atractylenolide III are relatively stable and are considered characteristic constituents of Baizhu with significant anti-inflammatory activity\cite{ref11,ref12}. Polysaccharides from Baizhu also contribute to its immunomodulatory effects\cite{ref13}.

Gancao (\textit{Glycyrrhizae Radix et Rhizoma}) is the dried root and rhizome of \textit{Glycyrrhiza uralensis} Fisch. and related species in the Fabaceae family. Its main active constituents are triterpenoid saponins and flavonoids. Among the saponins, glycyrrhizic acid is the most important component. It usually exists in the form of ammonium salts and is metabolized in vivo to glycyrrhetinic acid, which has a corticosteroid-like anti-inflammatory effect\cite{ref14,ref15}. The main flavonoids include liquiritin, isoliquiritin, liquiritigenin, isoliquiritigenin, and various chalcone derivatives\cite{ref16}.

Fresh ginger (\textit{Zingiberis Rhizoma Recens}) is the fresh rhizome of \textit{Zingiber officinale} Roscoe. It is rich in pungent phenolic compounds (gingerols) and volatile oils. Gingerols are responsible for the pungent taste of ginger and mainly include 6-gingerol, 8-gingerol, and 10-gingerol. These compounds have anti-inflammatory, antiemetic, and circulation-promoting effects\cite{ref17}. During heating, gingerols can undergo dehydration to form shogaols, such as 6-shogaol. The volatile oil fraction contains sesquiterpenes such as zingiberene and β-sesquiphellandrene\cite{ref18}.

Dazao (\textit{Jujubae Fructus}) is the dried ripe fruit of \textit{Ziziphus jujuba} Mill. in the Rhamnaceae family. It contains a wide variety of components, among which cyclic adenosine monophosphate (cAMP) and polysaccharides have attracted much attention. The cAMP content in jujube is much higher than in most other plants, and cAMP is an important second messenger involved in intracellular signal transduction\cite{ref19}. In addition, jujube contains triterpenic acids (such as oleanolic acid and ursolic acid, mainly in the fruit peel)\cite{ref20}, flavonoids, and various amino acids. These components together support the traditional functions of jujube in tonifying the middle Jiao, nourishing the blood, and calming the mind.

\section{Pharmacological effects and mechanisms}
In recent years, a large number of basic studies have revealed that Fangji Huangqi Decoction exerts its actions through multiple mechanisms, including anti-inflammatory effects, cardiovascular protection, renal protection, antitumor activity, and regulation of glucose and lipid metabolism.

\subsection{Anti-inflammatory effects}
One of the key functions of Fangji Huangqi Decoction is to ``tonify Qi and consolidate the exterior'' so as to strengthen the body's defense, which reflects the TCM concept of ``supporting healthy Qi to dispel pathogenic factors''. Inflammation is a basic pathological process in rheumatic pain and many chronic diseases. Lin et al.\cite{ref21} reported that Fangji Huangqi Decoction has clear, dose-dependent analgesic and anti-inflammatory effects in animal models, which may be related to inhibition of peripheral nociceptive pathways, such as suppression of prostaglandin synthesis. In models of autoimmune diseases such as rheumatoid arthritis (RA) and immune-mediated kidney disease, the decoction shows significant anti-inflammatory and immunoregulatory effects. Its anti-inflammatory action mainly involves inhibition of key inflammatory signaling pathways. Studies have shown that the decoction significantly lowers the levels of pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6. Mechanistically, it inhibits phosphorylation and degradation of IκBα in the NF-κB pathway, and reduces phosphorylation of p38 and JNK in the MAPK pathway, thereby suppressing the over-expression of inflammatory mediators at the transcriptional level\cite{ref22,ref23}. In inflammatory joint models, Fangji Huangqi Decoction can inhibit VEGF-driven angiogenesis in synovial tissues, reduce exudation of inflammatory substances, and improve joint swelling, redness, and deformity\cite{ref24}.

The formula also shows a bidirectional regulatory effect on the immune system. The combination of Huangqi and Baizhu (the core herb pair of Yupingfeng San) enhances non-specific immunity, for example by increasing macrophage phagocytic activity and natural killer (NK) cell function. In contrast, tetrandrine from Fangji suppresses excessive proliferation of activated T lymphocytes and reduces their cytokine production. When used together, these herbs strengthen the body's resistance to disease while preventing an excessive immune-inflammatory response, thus helping to maintain dynamic immune balance\cite{ref25,ref26}.

\subsection{Improvement of ventricular remodeling and myocardial fibrosis}
Myocardial fibrosis is a key pathological process in chronic heart failure (CHF). Experimental studies have shown that Fangji Huangqi Decoction can improve ventricular remodeling and myocardial fibrosis in animal models. Yang et al.\cite{ref27} found that medium and high doses of the decoction significantly improved myocardial histopathology in rats. The mechanism was associated with reduced levels of angiotensin II (Ang II), inhibition of p38MAPK phosphorylation, down-regulation of transforming growth factor-β1 (TGF-β1), and decreased synthesis of collagen I and collagen III. In the formula, tetrandrine acts as a natural calcium channel blocker. It can dilate coronary and peripheral blood vessels, lower blood pressure, and reduce cardiac afterload. Astragaloside IV has a positive inotropic effect, improves myocardial energy metabolism, and enhances contractile function \cite{ref28}. Cao et al.\cite{ref29} reported that quercetin, tetrandrine, astragaloside IV, and other components in the decoction can regulate pathways related to apoptosis and fatty acid metabolism. The decoction also attenuates norepinephrine-induced cardiomyocyte hypertrophy and reduces the mRNA expression of ANP and BNP, thereby improving ventricular remodeling.

\subsection{Antitumor effects}
Fangji Huangqi Decoction has shown potential as an adjuvant therapy for breast cancer. Liu et al.\cite{ref30} and Guo et al.\cite{ref31} demonstrated that the decoction inhibits proliferation and migration of triple-negative breast cancer MDA-MB-231 cells. Mechanistically, treatment with the decoction increases the expression of E-cadherin and reduces expression of mesenchymal markers such as vimentin, indicating inhibition of epithelial--mesenchymal transition (EMT). This contributes to suppression of tumor growth and angiogenesis. Further research has shown that tetrandrine, as an important active component in the formula, can activate the Hippo/YAP signaling pathway and induce apoptosis in breast cancer cells, which may be one of the main mechanisms underlying the antitumor effects of the decoction\cite{ref32}.

\subsection{Regulation of glucose and lipid metabolism}
For metabolic syndrome and obesity, Fangji Huangqi Decoction has both symptomatic and root-cause benefits in TCM terms. Jia et al.\cite{ref33} showed in a high-fat diet rat model that the decoction increases HDL cholesterol and reduces TG, total cholesterol, and free fatty acid levels, thereby improving insulin resistance. Chen et al.\cite{ref34} reported that the key mechanisms of the decoction in treating type 2 diabetes and metabolic disorders involve regulation of AMPK, AGE/RAGE, and FoxO signaling pathways, which promote energy metabolism and fatty acid oxidation. Experimental work also confirmed that Fangji Huangqi Decoction can inhibit T lymphocyte proliferation and lower levels of inflammatory cytokines \cite{ref35}. Using network pharmacology, molecular docking, and clinical studies, Jiang et al.\cite{ref36,ref37} further suggested that the decoction may exert its anti-obesity effects through multiple pathways including TNF, IL-17, apoptosis, p53, and HIF-1, thereby influencing inflammation, oxidative stress, and cell apoptosis.

\subsection{Renal protective effects}
Liu et al.\cite{ref38}, using network pharmacology combined with experimental validation, found that astragaloside IV and tetrandrine have a synergistic effect in protecting podocytes. They increase the expression of key slit diaphragm proteins Nephrin and Podocin and prevent their ubiquitin-mediated degradation, thus stabilizing podocyte structure, repairing the glomerular filtration barrier, and reducing protein leakage. Cao Guanghai et al.\cite{ref39} observed that the decoction lowers serum levels of retinol-binding protein (RBP) and reduces oxidative stress damage to the glomerular basement membrane. Song\cite{ref40} reported that Fangji Huangqi Decoction down-regulates the expression of Toll-like receptors TLR4 and TLR7, thereby inhibiting TLR-mediated renal micro-inflammation. Atractylenolides from Baizhu are important regulators of renal water handling. They modulate aquaporin expression, down-regulate AQP2 in renal tissue, and inhibit over-activation of the renin--angiotensin--aldosterone system (RAAS), leading to enhanced water and sodium excretion and a sustained diuretic effect\cite{ref41}. Tetrandrine, as a calcium channel blocker, dilates renal blood vessels and improves renal hemodynamics; it also inhibits mesangial cell proliferation by blocking calcium influx. Astragaloside IV reduces extracellular matrix deposition via the TGF-β1/Smad pathway, thereby slowing progression of tubulointerstitial fibrosis\cite{ref42,ref43}.

\section{Clinical research progress on Fangji Huangqi Decoction}
The clinical use of Fangji Huangqi Decoction reflects the TCM idea of ``treating different diseases with the same method''. It is mainly used in kidney diseases, cardiovascular diseases, rheumatic and joint diseases, and metabolic disorders.

\subsection{Kidney diseases}
Clinically, Fangji Huangqi Decoction is often used for primary nephrotic syndrome and chronic glomerulonephritis with patterns of spleen--kidney Qi deficiency and internal retention of water-dampness. Wang Tiesuo et al.\cite{ref44} used a modified Fangji Huangqi Decoction to treat refractory edema in nephrotic syndrome. The total effective rate in the treatment group reached 92.86\%, which was significantly higher than 71.43\% in the control group. The decoction reduced urinary protein and serum total cholesterol, increased serum albumin, and improved hypercoagulability. Meta-analyses and clinical observations\cite{ref45} suggest that combining Fangji Huangqi Decoction with standard Western treatments (such as glucocorticoids and immunosuppressants) can further reduce 24-hour urinary protein, raise plasma albumin, correct hypoproteinemia, and relieve edema. Its diuretic effect is mild and sustained, less likely to cause electrolyte imbalance, and it may help reduce adverse reactions caused by Western medicines\cite{ref46}. Chen Houbin et al.\cite{ref47} reported that, in patients with chronic nephritis or early hypertensive renal damage with Qi deficiency and dampness obstruction, modified Fangji Huangqi Decoction significantly improved edema and fatigue and helped protect renal function. Zhang Rui et al.\cite{ref48} found that the decoction improved glucose and lipid metabolism and reduced oxidative stress in patients with diabetic kidney disease, thus delaying disease progression.

\subsection{Rheumatic and joint diseases}
Fangji Huangqi Decoction is also widely used for rheumatoid arthritis and other rheumatic immune diseases, especially in patients who present with joint swelling, heavy limbs, and aversion to wind---symptoms that match the pattern of ``wind-damp obstruction with exterior deficiency and abundant dampness''. Clinical studies have shown that adding Fangji Huangqi Decoction to basic disease-modifying antirheumatic drugs such as methotrexate yields better results than Western medicine alone\cite{ref49}. Combination therapy more effectively reduces disease activity, as reflected by lower DAS28 scores, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), and also improves joint swelling, morning stiffness, and physical function. In addition, Fangji Huangqi Decoction can to some extent reduce adverse reactions of methotrexate, such as elevated liver enzymes and gastrointestinal discomfort, showing a ``synergistic and toxicity-reducing'' benefit of TCM\cite{ref50}. Li Runmin et al.\cite{ref51} reported that Fangji Huangqi Decoction combined with Wuling San was effective in treating knee osteoarthritis, and Yang Gongxu\cite{ref52} successfully used the decoction in acute gouty arthritis. In both conditions, it showed good effects in reducing swelling and relieving pain.

\subsection{Cardiovascular diseases}
Experimental and clinical studies indicate that Fangji Huangqi Decoction can increase urine output, improve cardiac function classification (NYHA), and lower plasma BNP levels\cite{ref53}. Liu Jie et al.\cite{ref54} observed that, in patients with chronic heart failure of Qi deficiency, blood stasis, and phlegm-fluid retention type, treatment with Sijunzi Decoction plus Fangji Huangqi Decoction significantly improved NYHA class. Fang Xiaojiang et al.\cite{ref55} expanded these findings and showed that modified Fangji Huangqi Decoction is also effective in heart failure with preserved ejection fraction. It is especially suitable for congestive heart failure with lower limb edema.

\subsection{Metabolic diseases (obesity)}
From a TCM perspective, obesity is often regarded as ``deficiency in root and excess in manifestation'', mainly involving spleen deficiency with dampness and phlegm retention. Fangji Huangqi Decoction promotes weight loss by tonifying Qi, strengthening the spleen, promoting diuresis, and resolving phlegm. Its clinical efficacy is closely related to improvements in lipid profiles (TC, TG, LDL-C) and reduction of low-grade inflammation\cite{ref56}. Li Yajuan et al.\cite{ref57} reported that Fangji Huangqi Decoction combined with meridian-based abdominal massage achieved a total effective rate of 94.1\% in patients with spleen-deficiency and dampness-retention type simple obesity, with significant reductions in body weight, BMI, and waist circumference. Ling Qinliang et al.\cite{ref58} showed that combining the decoction with Qiwei Baizhu Powder modulated the gut microbiota in obese children (for example, promoting the growth of \textit{Bacteroides} species) and reduced body fat percentage.

\section{Systematic Prediction of Q-Markers for Fangji Huangqi Decoction Based on the Five Principles}
As described above, we combined chemical, pharmacological, and clinical information with the Q-Marker concept to screen potential quality markers for Fangji Huangqi Decoction. The overall analysis path is shown in Figure 1.

\begin{figure}[htbp]
\centering
\includegraphics[width=0.8\textwidth]{qmarker_analysis_path.png}
\caption{Prediction analysis path of Q-Markers for Fangji Huangqi Decoction. Note: The study starts from the six component herbs and their main chemical groups. Then it applies the five Q-Marker principles: Transmissibility and traceability: select components that can be traced from raw herbs through decoction to measurable forms in plasma or target tissues; Specificity: prioritize components with high species specificity that can distinguish genuine herbs from adulterants; Efficacy: select components with clear evidence supporting their contribution to key actions such as tonifying Qi, promoting diuresis, and reducing inflammation; Compatibility environment: consider the behavior of components in the multi-herb decoction, including solubility changes, interactions, and stability; Measurability: ensure that candidate markers are stable and can be accurately measured by standard analytical methods. Through this step-by-step screening, we finally determined a set of ten core Q-Markers.}
\label{fig:qmarker_path}
\end{figure}

\subsection{Prediction Based on Transmissibility and Traceability}
We used ``Fangji,'' ``Huangqi,'' ``Baizhu,'' ``Gancao,'' ``Shengjiang,'' and ``Dazao'' as keywords to search the TCMSP database (Traditional Chinese Medicine Systems Pharmacology Database, https://old.tcmsp-e.com/tcmsp.php). The database lists 50 components for Fangji, 87 for Huangqi, 55 for Baizhu, 280 for Gancao, 265 for fresh ginger, and 133 for jujube. Using oral bioavailability (OB) $\geq$ 30\% and drug-likeness (DL) $\geq$ 0.18 as screening criteria, we obtained 3 candidate components for Fangji, 20 for Huangqi, 7 for Baizhu, 92 for Gancao, 5 for fresh ginger, and 29 for jujube.

Understanding the absorption, distribution, metabolism, and excretion (ADME) of components in a formula is essential for identifying the real active substances and explaining the mechanisms of action. In previous work, UPLC--MS/MS and other techniques were used to measure plasma concentration--time curves of prototype components such as tetrandrine, astragaloside IV, and glycyrrhizic acid after oral administration of Fangji Huangqi Decoction in rats. The results showed that these compounds can be absorbed into the blood in prototype form, but they differ in time to peak concentration (Tmax), elimination half-life (t½), and bioavailability. This suggests that they may differ in onset time, intensity, and duration of action. These pharmacokinetic differences also reflect the multi-component, multi-target, and time-sequence synergistic features of the formula\cite{ref59}.

The liver is the main organ for drug metabolism. Many components in Fangji Huangqi Decoction are activated or inactivated by hepatic enzymes, such as the cytochrome P450 family. For example, glycyrrhizic acid is hydrolyzed by intestinal flora and liver enzymes to glycyrrhetinic acid, which has stronger activity. Analysing metabolic profiles in serum, urine, or tissues after administration and identifying characteristic metabolites is very important for understanding the overall effects of the formula at a system level\cite{ref60}.

\subsection{Prediction Based on Specificity}
Tetrandrine and fangchinoline are characteristic bisbenzylisoquinoline alkaloids of \textit{Stephania tetrandra} and are not present in \textit{Aristolochia} species. They are thus ideal for distinguishing true Fangji from toxic Guangfangji. Astragaloside IV and calycosin-7-O-β-D-glucoside are representative saponin and flavonoid markers of \textit{Astragali Radix}. Atractylenolide I/III distinguish Baizhu from Cangzhu. Glycyrrhizic acid and liquiritin are typical constituents of Gancao. 6-Gingerol and cAMP can serve as characteristic markers for fresh ginger and jujube, respectively. Together, these markers can trace the origin of all six herbs in the formula\cite{ref3,ref4,ref5,ref6,ref7,ref8,ref9,ref10,ref11,ref12,ref61,ref62,ref63,ref64,ref65,ref66,ref67,ref68,ref69,ref70,ref71,ref72}.

\subsection{Prediction Based on Efficacy}
Each selected marker is closely related to at least one key pharmacological action of the decoction: tetrandrine and fangchinoline: diuretic, anti-inflammatory, renoprotective; astragaloside IV and calycosin-7-O-β-D-glucoside: immunomodulatory, anti-fibrotic, cardioprotective; atractylenolide I/III: spleen-strengthening, anti-inflammatory; glycyrrhizic acid and liquiritin: anti-inflammatory, detoxifying, harmonizing; 6-gingerol and cAMP: promoting circulation, supporting energy metabolism, and modulating immunity\cite{ref73,ref74,ref75}.

\subsection{Prediction Based on the Compatibility Environment}
The clinical effectiveness of a classical formula depends on the interactions among its herbs. Fangji--Huangqi (chief--chief pairing): Studies suggest that astragalus polysaccharides can improve the solubility and absorption of alkaloids from Fangji. Astragaloside IV and tetrandrine also show clear synergistic effects in protecting podocytes and reducing kidney injury \cite{ref76,ref77}. Huangqi--Baizhu (chief--deputy pairing): This pair is also the core of the classical formula Yupingfeng San. When used together, they enhance the effects of tonifying Qi and strengthening the spleen. Atractylenolides and total astragalus saponins have synergistic effects on regulating immune function \cite{ref78}. Shengjiang--Dazao (assistant--envoy pairing): Ginger and jujube used together can reduce the side effects of the bitter-cold nature of Fangji on the stomach, improve spleen and stomach function, and help the absorption of other macromolecular components in the formula. These findings support the idea that the compatibility environment in the decoction should be considered when deciding whether a component can serve as a Q-Marker.

\subsection{Prediction Based on Measurability}
In addition to pharmacological relevance, candidate Q-Markers must be practical for routine quality control. The selected components---tetrandrine, fangchinoline, astragaloside IV, calycosin-7-O-β-D-glucoside, atractylenolide I, atractylenolide III, glycyrrhizic acid, liquiritin, and 6-gingerol---have all been recorded in the Chinese Pharmacopoeia or widely reported in the literature. Reliable HPLC-UV, HPLC-ELSD, or LC--MS methods have been established for their quantitative determination, and they show good stability under normal processing and storage conditions\cite{ref3}. Therefore, they are suitable as index components in industrial quality control of Fangji Huangqi Decoction and its preparations.

\subsection{Final Determination of Q-Markers}
By combining the five principles---transmissibility and traceability, specificity, efficacy, compatibility environment, and measurability---we propose the following compounds as Q-Markers for Fangji Huangqi Decoction:

Core markers: tetrandrine and fangchinoline (from Fangji, the chief herb, mainly responsible for promoting urination and reducing inflammation, and also important for safety control), and astragaloside IV (from Huangqi, the chief herb for tonifying Qi and protecting the kidney).

Characteristic markers: atractylenolide I and III (from Baizhu, the deputy herb, reflecting its spleen-tonifying and dampness-removing actions), and calycosin-7-O-β-D-glucoside (a characteristic flavonoid from Huangqi).

Auxiliary/harmonizing markers: glycyrrhizic acid and liquiritin (from Gancao, the assistant/envoy herb, with anti-inflammatory and detoxifying effects), 6-gingerol (a typical component of fresh ginger), and cAMP (a characteristic component of jujube).

Atractylodin was not selected because it is unstable, easily lost during decoction, and has low exposure in blood. Astragalus polysaccharides are important for immunoregulation, but as complex mixtures they are difficult to characterize and quantify accurately, so they are recommended as auxiliary indicators rather than main Q-Markers.

In summary, ten compounds are finally determined as core Q-Markers of Fangji Huangqi Decoction. Their detailed information is shown in Tables 1 and 2.

\begin{tmrtable}{Potential Quality Markers of Fangji Huangqi Decoction}{tab:qmarkers}{X[l]X[l]X[l]X[l]}{1}{
No. & Name & Molecular formula & CAS number & Source herb \\
1 & Tetrandrine & C$_{38}$H$_{42}$N$_{2}$O$_{6}$ & 518-34-3 & Fangji \\
2 & Fangchinoline & C$_{37}$H$_{40}$N$_{2}$O$_{6}$ & 436-77-1 & Fangji \\
3 & Astragaloside IV & C$_{41}$H$_{68}$O$_{14}$ & 84687-43-4 & Huangqi \\
4 & Calycosin-7-O-β-D-glucoside & C$_{22}$H$_{22}$O$_{10}$ & 20633-67-4 & Huangqi \\
5 & Atractylenolide I & C$_{15}$H$_{18}$O$_{2}$ & 73069-13-3 & Baizhu \\
6 & Atractylenolide III & C$_{15}$H$_{20}$O$_{3}$ & 73030-71-4 & Baizhu \\
7 & Glycyrrhizic acid & C$_{42}$H$_{62}$O$_{16}$ & 1405-86-3 & Gancao \\
8 & Liquiritin & C$_{21}$H$_{22}$O$_{9}$ & 551-15-5 & Gancao \\
9 & 6-Gingerol & C$_{17}$H$_{26}$O$_{4}$ & 23513-14-6 & Fresh ginger \\
10 & cAMP & C$_{10}$H$_{12}$N$_{5}$O$_{6}$P & 60-92-4 & Jujube
}{Note: All compounds meet the five Q-Marker principles for Fangji Huangqi Decoction.}

\begin{tmrtable}{Predictive Analysis of Potential Quality Markers (Q-Marker) for Fangji Huangqi Decoction}{tab:qmarker_analysis}{X[l]X[l]X[l]X[l]X[l]}{1}{
Component & Source & Basis for transmissibility and traceability & Basis for specificity & Basis for efficacy & Role in the formula & Analytical method \\
Tetrandrine & Fangji & Rapid oral absorption, high plasma level, main absorbed alkaloid & Characteristic bisbenzylisoquinoline alkaloid of \textit{Stephania tetrandra}; helps distinguish from aristolochic-acid-containing adulterants & Calcium-channel blocking, diuretic, anti-inflammatory, immunoregulatory & Chief herb; shows synergy with Huangqi & HPLC-UV; listed in Pharmacopoeia \\
Fangchinoline & Fangji & Similar pharmacokinetics to tetrandrine; relatively high bioavailability & Coexists with tetrandrine; structurally similar and chemically specific & Diuretic and anti-inflammatory synergy & Part of chief-herb components & HPLC-UV; listed in Pharmacopoeia \\
Astragaloside IV & Huangqi & Bioavailability improved in the compound environment; detectable in plasma & Specific triterpenoid saponin of \textit{Astragalus} genus; strong species specificity & Immuno-enhancing, anti-fibrotic, cardio-protective & Chief herb; key compound for tonifying Qi and strengthening the exterio & HPLC-ELSD/UV; included in Pharmacopoeia \\
Calycosin-7-O-β-D-glucoside & Huangqi & Main blood-absorbed flavonoid; pharmacokinetics clearly defined & Representative and stable isoflavone component of Huangqi & Antioxidant, anti-inflammatory, immuno-regulatory & Auxiliary compound of the chief herb & HPLC-UV; validated in literature \\
Atractylenolide I & Baizhu & Detectable in plasma; moderate half-life & Characteristic sesquiterpene lactone distinguishing Baizhu from Cangzhu & Anti-inflammatory, regulatory to gastrointestinal function & Minister herb; basis for spleen-strengthening and damp-drying actions & HPLC-UV; validated in literature \\
Atractylenolide III & Baizhu & Pharmacokinetics similar to atractylenolide I; good stability & Co-exists with atractylenolide I as a characteristic marker & Anti-inflammatory, immuno-modulatory & Part of minister-herb component & HPLC-UV; listed in Pharmacopoeia \\
Glycyrrhizic acid & Gancao & Metabolized in vivo to glycyrrhetinic acid; clear systemic exposure & Characteristic triterpenoid saponin of \textit{Glycyrrhiza} species; high abundance & Anti-inflammatory, detoxifying, harmonizing other herbs & Envoy herb, also serves an assistant function & HPLC-UV; listed in Pharmacopoeia \\
Liquiritin & Gancao & Absorbed and metabolized to liquiritigenin; measurable in plasma & Major flavone glycoside of Gancao & Anti-inflammatory, antioxidant, mucosal protective & Assistant compound of envoy herb & HPLC-UV; listed in Pharmacopoeia \\
6-Gingerol & Fresh ginger & Good oral absorption; reaches effective plasma concentrations & Characteristic pungent component of fresh ginger; distinguishes it from dried ginger & Anti-inflammatory, circulation-promoting, anti-emetic & Assistant herb; harmonizes ying and wei Qi & HPLC-UV; standardized method available \\
cAMP & Jujube & Absorbed into blood; participates in cellular signal transduction & Remarkably high content in jujube compared with other plants & Regulates immune response, energy metabolism, and anti-fatigue activity & Envoy herb; supports Qi-tonifying and blood-nourishing actions & HPLC-UV / LC-MS
}{Note: All components fulfill the five Q-Marker principles and are suitable for quality control of Fangji Huangqi Decoction.}

\section{Discussion}
Our review confirms that Fangji Huangqi Decoction has a clear material basis and a wide range of pharmacological activities that support its traditional indications. The main active groups include alkaloids from Fangji, saponins and flavonoids from Huangqi and Gancao, sesquiterpene lactones from Baizhu, and gingerols and cAMP from ginger and jujube. By applying the five-principle Q-Marker framework, we further narrowed down the candidate components to ten core compounds: tetrandrine, fangchinoline, astragaloside IV, calycosin-7-O-β-D-glucoside, atractylenolide I, atractylenolide III, glycyrrhizic acid, liquiritin, 6-gingerol, and cAMP.

These components fulfill the conditions of being: traceable from raw herbs to decoction and into the body; specific for their respective herbs and useful in distinguishing genuine materials; clearly linked to important pharmacological effects such as diuresis, immunomodulation, anti-inflammation, and metabolic regulation; stable and meaningful in the multi-herb compatibility environment; and measurable using standard HPLC or LC--MS methods. This set of proposed Q-Markers covers all six herbs and reflects the ``chief--deputy--assistant--envoy'' structure of the formula. It is more comprehensive than traditional standards that focus on only one or two marker compounds, and better connects the material basis with both efficacy and safety.

However, some issues require further study. For example, 6-gingerol can be converted to 6-shogaol during decoction, and it is still unclear whether the prototype, the metabolite, or the sum of both should be used as the quality indicator. The cAMP content of jujube is influenced by origin, harvest time, and storage conditions, and still needs large-scale data to define reasonable limits. In addition, most of the evidence used in our analysis comes from separate studies on single herbs or small combinations, and direct spectrum--effect and serum pharmacochemistry data for the whole decoction remain limited.

\section{Conclusions}
Fangji Huangqi Decoction is a time-tested classical prescription that has been successfully applied to a variety of kidney, cardiovascular, rheumatic, and metabolic diseases. Modern pharmacology and clinical studies support its traditional use and indicate multi-target mechanisms. Through a systematic review and Q-Marker-based analysis, we propose ten core Q-Markers for Fangji Huangqi Decoction: tetrandrine, fangchinoline, astragaloside IV, calycosin-7-O-β-D-glucoside, atractylenolide I, atractylenolide III, glycyrrhizic acid, liquiritin, 6-gingerol, and cAMP. This set of markers can serve as a foundation for developing multi-component quality standards and for guiding future research on the formula's pharmacodynamics and clinical optimization.

Future work should include: (1) establishing UPLC--MS/MS methods for simultaneous determination of these markers in raw herbs, decoctions, and preparations; (2) building chromatographic fingerprint--efficacy correlation models in relevant disease models; and (3) validating the relationship between Q-Marker levels and clinical outcomes in well-designed clinical trials.

\begin{acknowledgement}
No specific funding was received for this work.
\end{acknowledgement}

\section*{Author Contributions}
Conceptualization: Gaofei Yan, Huiying Li. Literature search and data collection: Gaofei Yan, Peng Yu. Data analysis and interpretation: Xianzhong Bu, Zhengguo Wang. Drafting of the manuscript: Gaofei Yan. Critical revision of the manuscript: Huiying Li. All authors read and approved the final manuscript and agree to be accountable for all aspects of the work.

\section*{Abbreviations and Terminology}
ADME -- Absorption, Distribution, Metabolism and Excretion; pharmacokinetic processes determining the in vivo fate of a compound. \\
AGE/RAGE -- Advanced Glycation End products and their Receptor; signaling axis implicated in inflammation, oxidative stress and diabetic complications. \\
AMA -- American Medical Association; citation and reference style used in this manuscript. \\
AMPK -- AMP-activated Protein Kinase; a central regulator of cellular energy metabolism. \\
ANP -- Atrial Natriuretic Peptide; cardiac hormone and biomarker related to cardiac load. \\
AQP -- Aquaporin; family of water channel proteins (e.g., AQP1--4) involved in renal water handling. \\
BNP -- Brain Natriuretic Peptide; biomarker of heart failure and ventricular stress. \\
cAMP -- Cyclic Adenosine Monophosphate; intracellular second messenger found at high levels in jujube. \\
CHF -- Chronic Heart Failure. \\
CKD -- Chronic Kidney Disease. \\
cAMP -- Cyclic Adenosine Monophosphate; second messenger involved in multiple signaling pathways, relatively abundant in jujube. \\
CRP -- C-reactive Protein; clinical marker of systemic inflammation. \\
DAS28 -- Disease Activity Score in 28 joints; composite index to assess rheumatoid arthritis activity. \\
DBD / DKD -- Diabetic Kidney Disease. \\
EMT -- Epithelial--Mesenchymal Transition; process linked to tumor invasion and metastasis, and tissue fibrosis. \\
ETM / EMT -- Epithelial--Mesenchymal Transition (same as above). \\
FoxO -- Forkhead box O; transcription factor family involved in oxidative stress, apoptosis and metabolism. \\
HIF-1 -- Hypoxia-Inducible Factor-1; transcription factor responding to hypoxic stress. \\
HGWD -- Huangqi Guizhi Wuwu Decoction; a classical formula used in neuropathic pain and circulatory disorders. \\
HPLC -- High-Performance Liquid Chromatography. \\
HPLC-MS/MS / LC-MS/MS -- Liquid Chromatography--Tandem Mass Spectrometry. \\
IgAN -- IgA Nephropathy. \\
IL-1β, IL-6, IL-17 -- Interleukin-1 beta, Interleukin-6, Interleukin-17; pro-inflammatory cytokines. \\
MAPK -- Mitogen-Activated Protein Kinase; signaling pathway involved in inflammation, proliferation and stress responses. \\
MTX -- Methotrexate; disease-modifying antirheumatic drug (DMARD). \\
NF-κB -- Nuclear Factor kappa B; transcription factor that regulates inflammatory and immune responses. \\
NK cells -- Natural Killer cells; innate immune effector cells. \\
NS -- Nephrotic Syndrome. \\
NYHA -- New York Heart Association functional classification for heart failure. \\
OA -- Osteoarthritis. \\
PPARγ -- Peroxisome Proliferator-Activated Receptor gamma; nuclear receptor involved in lipid metabolism and inflammation. \\
RA -- Rheumatoid Arthritis. \\
RAAS -- Renin--Angiotensin--Aldosterone System; hormonal system regulating blood pressure and fluid balance. \\
RBP -- Retinol-Binding Protein; can be used as a marker of tubular injury and renal oxidative damage. \\
RTK-PKCα -- Receptor Tyrosine Kinase--Protein Kinase C alpha signaling axis. \\
TC -- Total Cholesterol. \\
TCM -- Traditional Chinese Medicine. \\
TG -- Triglycerides. \\
Th1/Th2 -- T helper 1 / T helper 2 lymphocyte subsets; reflect cellular vs humoral immune responses. \\
TGF-β1 -- Transforming Growth Factor-beta1; key profibrotic cytokine. \\
TLR4, TLR7 -- Toll-Like Receptor 4 and 7; pattern recognition receptors involved in innate immunity and renal micro-inflammation. \\
TNF-α -- Tumor Necrosis Factor-alpha; major pro-inflammatory cytokine. \\
UHPLC / UPLC -- Ultra-High-Performance Liquid Chromatography. \\
UPLC-Q-TOF-MS / UPLC-QTOF-MS -- Ultra-Performance Liquid Chromatography coupled with Quadrupole Time-of-Flight Mass Spectrometry. \\
VEGF -- Vascular Endothelial Growth Factor; key mediator of angiogenesis. \\
WGCNA -- Weighted Gene Co-expression Network Analysis; bioinformatics method to analyze gene expression modules. \\
YAP -- Yes-Associated Protein; key effector in the Hippo signaling pathway. \\

TCM-specific terms (for clarity to international readers) \\
Fangji Huangqi Decoction (Fangji Huangqi Tang) -- Classical TCM formula composed of \textit{Stephania tetrandra} (Fangji), \textit{Astragalus membranaceus} (Huangqi), \textit{Atractylodes macrocephala} (Baizhu), \textit{Glycyrrhiza uralensis} (Gancao), fresh ginger and jujube; used to treat ``wind--water'' patterns with Qi deficiency and dampness retention. \\
Qi -- Vital energy or functional activity in TCM theory. \\
Ying and Wei -- Nutritive (Ying) Qi and Defensive (Wei) Qi; concepts describing internal nourishment and external defense in TCM. \\
Spleen deficiency with dampness retention -- TCM pattern characterized by impaired transformation and transportation of fluids, leading to edema, heaviness and obesity. \\
Wind--damp Bi syndrome -- TCM pattern of painful obstruction with joint pain, swelling and heaviness due to wind, cold and dampness invading the channels.

\section*{Conflicts of Interest}
The authors declare that they have no conflicts of interest related to this work.

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