IngredientsSemen Astragali Complanati (SAC), alternatively known as Flatstem Milkvetch Seed or Sha Yuan Zi in Chinese, is the dried ripe seed of Flatstem Milkvetch (Astragalus complanatus Bunge) of the family Leguminosae, and is commonly used in traditional Chinese medicine (TCM) for treating muscle, liver, kidney, blood, skin, and reproductive system diseases.
Astragalus complanatus Bunge is a perennial herb within the family Fabaceae (order Fabales), widely distributed in China's Gansu, Hebei, Henan, Jiangsu, Jilin, Ningxia, Qinghai, Shaanxi, Shanxi, and Sichuan provinces at elevations of 1,000–1,700 m.
A notable taxonomic issue surrounds the species. Over 50 reviewed articles have used an incorrect scientific name, Astragalus complanatus R.Br., for Flatstem Milkvetch, which is the source of SAC. The problem of using an incorrect scientific name was found to be very serious in Flatstem Milkvetch, as incorrect herb-source names may mislead readers and propagate errors. Reports have shown that seeds of some Astragalus species such as Astragalus sinicus L. and Astragalus adsurgens Pall. are sold as SAC in the market.
Astragalus is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. There are 278 recognized species of Astragalus in China, along with two subtypes and 35 variants.
The plant is known by several names across different contexts:
Genuine SAC is brownish-green or greyish-brown, reniform but slightly flattened, with a smooth surface. The seeds are collected from late autumn to early winter and dried in the sun. The collected dried seeds are usually processed with salt water before use.
According to the China Pharmacopoeia 2020 Edition, Astragali Complanati Semen (ASC) — the dried ripe seed of Astragalus complanatus R. Br. — is one of only two Astragalus-derived materials permitted for use as a nationally recognized medicinal drug in China. Astragali Complanati Semen is also recorded in the Hong Kong Materia Medica Standards and is commonly used by Chinese medicine practitioners to tonify the "kidney" and assist "yang," secure essence to reduce urination, and nourish "liver" to improve eyesight.
Semen Astragali Complanati has long been considered a health-keeping foodstuff in Chinese culture and was officially indexed in the Pharmacopoeia of the People's Republic of China due to its health-promoting and medical functions.
The plant material is used in several forms:
The classical formula Jin Suo Gu Jing Wan (Metal Lock Pill to Stabilize Essence) contains Sha Yuan Zi together with Euryale Seed, Lotus Seed, Dragon Bone, and Oyster Shell; it nourishes the kidneys and secures essence, and is used for treating spermatorrhea, seminal emissions, and weakness of the lower back due to kidney deficiency.
China has a long history of utilizing Astragalus species, with use first documented in the Shennong Materia Medica. Evidence suggests that the use of Astragalus dates back to the Qin and Han dynasties (221 BC – AD 202).
The earliest documented mention of Sha Yuan Zi appears in the Kaibao Bencao (Kaibao Materia Medica), where it was noted for addressing male kidney deficiency with spermatorrhea and female vaginal discharge. Over time, Chinese medical scholars such as Li Shizhen in the Ming Dynasty expanded upon Sha Yuan Zi's uses in his Compendium of Materia Medica (Bencao Gangmu), describing its appearance, growing regions, and effects including nourishing the kidneys, securing essence, improving vision, and enhancing hearing. Later texts such as Bencao Beiyao and Bencao Zhengyi further refined its applications, making Sha Yuan Zi a widely used herb in clinical practice.
The seeds of Astragalus complanatus, a traditional Chinese medicine, have been extensively used for the clinical treatment of liver and kidney complaints and tumors for more than a thousand years. It was described as warm and sweet in the most authoritative medical book of ancient China, the Compendium of Materia Medica.
The application of SAC in TCM includes the treatment of a number of diseases such as muscle diseases (including child myasthenia gravis), liver and kidney diseases ("yin" deficiency of "liver" and "kidney"), blood diseases (heat blood and wind-dry), skin diseases (vitiligo), and reproductive system diseases (spermacrasia, asthenospermia, azoospermia, testicular spasm, metrorrhagia, and metrostaxis).
In TCM, ACS is believed to warm and replenish the liver and kidney, strengthen meridians, and reduce urination, and it is mostly used to treat symptoms such as dizziness, sore waist and knees, frequent urination, premature ejaculation, nocturnal emission, and excessive leucorrhoea in women.
ACS has the TCM functions of tonifying the kidney, supporting yang, consolidating essence, reducing urine, nourishing the liver, and brightening the eyes, and it is mainly used for kidney deficiency, low back pain, premature ejaculation, frequent enuresis, white turbidity, and dizziness.
Astragali complanati semen (Shayuanzi), the dried ripe seed collected in late fall to early winter, is listed in the Chinese Pharmacopoeia and is used as a tonic against polyuria, applied as a sedative, hypotensive, and diuretic herbal drug. The water infusion has also been used for the treatment of hypertension of the 1st and 2nd stages, cardiovascular insufficiency, and chronic nephritis.
ACS has been used traditionally to tonify yang, strengthen the kidney, and consolidate kidney qi in TCM theory, resulting in the stabilization of the essence; this relates to conditions such as seminal emission, spermatorrhea, enuresis, frequent urination, leukorrhagia, and lumbar pain.
Flat-stem milk-vetch is primarily used in traditional Chinese medicine as a tonic herb to support vitality and combat fatigue. Historical texts and ethnobotanical sources describe its use in formulas aimed at strengthening "qi" (vital energy), particularly in individuals experiencing weakness, tiredness, or general debility.
The major contents of SAC include fatty acids, amino acids, polysaccharides, flavonoids, triterpene glycosides, and trace elements. Previous scientific studies have reported that SAC exhibits a number of therapeutic effects on chronic diseases such as cardiovascular diseases, diabetes mellitus, and cancers. Flavonoids have been identified as the main bioactive component in SAC.
To date, proteins, amino acids, fatty acids, polysaccharides, phenols, sterols, alkaloids, triterpenoids, flavonoids, and trace elements of ACS have been reported.
Flavonoids represent the largest group of polyphenolic compounds occurring in Astragalus species. Many different subclasses of flavonoids have been described from the genus Astragalus including flavones, flavonols, flavanones, flavanonols, chalcones, aurones, isoflavones, isoflavanes, and pterocarpans.
The total flavonoids from ACS (TFACS), which include complanatoside A, myricetin-3-O-β-d-glucoside, and calycosin-7-O-glucoside, are the main active components of ACS.
Among the specific flavonoid compounds found in Astragalus complanatus seeds, complanatin is the plant's namesake unique compound. A novel flavonoid glycoside acylated with a sesquiterpene, dihydrophaseic acid, was obtained from the seeds of Astragalus complanatus R. Br.; this compound was named complanatin. Phytochemical investigation of the seeds of Astragalus complanatus revealed the presence of complanatin — a new rhamnocitrin glycoside acylated with an acidic-type sesquiterpene. A glycoside similar to complanatin was isolated together with two other rhamnocitrin glycosides acylated with p-coumaric and ferulic acid.
The main chemical constituents of Astragali Complanati Semen (ACS) are flavonoid glycosides (flavonol glycosides, isoflavone glycosides, and acylated flavonol glycosides), fatty acids, and triterpene saponins.
Specific identified flavonoid constituents include:
Chemical constituents of ACS extract analyzed by ultra-performance liquid chromatography coupled with electrospray ionization orbitrap mass spectrometry showed that ACS extract mainly consists of phenolic compounds including flavonoids and flavonoid glycosides.
A homogeneous galactomannan (45.0 kDa) was isolated from the seeds of Astragalus complanatus R. Br. Structural analysis revealed that it was composed of T-galactose (Gal), 1,4-mannose (Man), and 1,4,6-Man in a molar ratio of 1.47:1.00:1.42, featuring a β-1,4-Manp backbone with terminal α-Galp branches at O-6 of Manp. Its triple-helical structure was confirmed by Congo red assay and circular dichroism spectrum.
Beyond flavonoids and polysaccharides, the phytochemical profile of ACS encompasses:
Total flavonoids from ACS (TFACS), which include complanatoside A, myricetin-3-O-β-d-glucoside, and calycosin-7-O-glucoside, are the main active components of ACS. Recent pharmacological studies have shown that TFACS has anti-inflammatory, antioxidant, hepatoprotective, antitumour, and antifibrotic effects.
In rat studies, in the ACF (Astragalus complanatus flavonoid) groups, superoxide dismutase (SOD) activity increased and malondialdehyde (MDA) content decreased in comparison to the liver fibrosis model group, and serum PINP and PIIINP contents in the ACF-2 and ACF-3 groups decreased compared to those in the model group. These changes indicate reduction of oxidative stress and inhibition of collagen precursor synthesis.
ACS extract was tested and found to be rich in antioxidants, which may be attributed to its high content of phenolic compounds.
Antifibrotic effects of flavonoids from A. complanatus in in vivo experiments with rats with induced liver fibrosis were observed. The antifibrotic mechanisms of the flavonoids were related to their influence on lipid peroxidation and collagen synthesis and degradation.
A novel polysaccharide isolated from the seeds of Astragalus complanatus exerted potent anti-fibrotic effects, suppressing hepatic stellate cells (HSCs) activation in vitro and attenuating CCl₄-induced liver injury in vivo.
Flavonoids and related compounds from ACS promote the proliferation and enhancement of the cytotoxicity of natural killer (NK) cells against K562 and SMMC-7721 cells. They also regulate the expression of cell surface markers, improving the identification and killing capabilities of NK cells. Additionally, flavonoids increase the expression of the receptors CD314 and CD336, thereby enhancing the immune activity of NK cells. Furthermore, they elevate the production of IFN-γ following the stimulation of NK-92 cells by K562 cells, with the increased secretion of IFN-γ contributing to the enhancement of immune regulation and anti-tumor functions of natural killer cells.
Consumption of ACS remarkably suppressed elevated total cholesterol (p < 0.01) and LDL-C (p < 0.001) induced by high cholesterol diet in a rat model. Based on serum fatty acid profiles analyzed by gas chromatography–mass spectrometry, free and esterified fatty acids including docosapentaenoic acid, adrenic acid, dihomo-γ-linolenic acid, and arachidonic acid were regulated in the ACS treatment group. Western blot results further indicated that the protein expression of peroxisome proliferator-activated receptor alpha (PPARα) in liver was upregulated in the ACS treatment group.
The flavonoid fraction obtained from the seeds of Astragalus complanatus showed a significant radioprotective effect against damage induced by γ-irradiation in mice. The flavonoid fraction increased the survival rate of experimental animals and allowed the damaged organ to recover normal appearance, with a mechanism of enhancing immunity and blood-producing function. This activity of the flavonoids could be explained with the reduction of DNA injury and mutation in vitro.
Overview: Astragalus complanatus is a widely used herbal material in traditional Chinese medicine that has been extensively used for treating liver and kidney complaints. Many studies indicate that it has the functions of anti-liver fibrosis, inhibiting platelet aggregation, reduction of serum lipids, anti-peroxidation of lipids, anti-inflammatory, anti-tumor, immune enhancement, and protection against hepatic injury.
Animal evidence: In a rat study examining anti-liver fibrosis effects of Astragalus complanatus flavonoids (ACF), a liver fibrosis model was established by intraperitoneally injecting 0.2 mL/100 g of 0.5% dimethylnitrosamine three times per week. Rats were administered ACF at doses of 30, 60, or 120 mg/kg, or colchicine (0.1 mg/kg) once a day for 1 month. Serum N-propeptide of type I procollagen (PINP) and type III procollagen (PIIINP) were measured using ELISA. Malondialdehyde (MDA) and superoxide dismutase (SOD) in hepatic tissue were evaluated, and MMP-1 mRNA expression was assayed by RT-PCR. Results indicated reduced fibrotic markers and improved oxidative balance.
Recent pharmacological studies have shown that TFACS has anti-inflammatory, antioxidant, hepatoprotective, antitumour, and antifibrotic effects. TFACS can decrease the MDA content and increase SOD activity, decrease serum PINP and PIIINP contents, and upregulate the gene expression of MMP-1.
Previous studies showed that the flavonoid component from the seeds of Astragalus complanatus (FAC) is mainly an active constituent and has hepatoprotective effect, anti-liver fibrosis, and anti-tumor and immune enhancement properties.
Evidence strength: Predominantly preclinical (in vitro and rodent models). No adequately powered controlled clinical trials in humans have been published specifically for ACS in liver fibrosis. Evidence is preliminary.
Animal/preclinical evidence: Studies have examined the effect of the total flavonoid fraction of Astragalus complanatus R. Brown on angiotensin II–induced portal-vein contraction in hypertensive rats. Antihypertensive effects of the total flavonoid fraction of Astragalus complanatus R. Brown were studied in hypertensive rats.
ACS also possesses anti-hypertensive and anti-fibrosis activities.
The water infusion of ACS has been used for the treatment of hypertension of the 1st and 2nd stages, cardiovascular insufficiency, and chronic nephritis. These applications are drawn from ethnopharmacological use and preclinical data.
Evidence strength: Animal and in vitro data only. Antihypertensive effects have not been demonstrated in properly controlled human clinical trials specific to Astragalus complanatus. Evidence is preliminary and requires human validation.
The hypocholesterolemic protective effect of the dried seed of Astragalus complanatus was investigated in rats fed a normal diet, a high-cholesterol diet (HCD), and an HCD plus 70% ethanol extract of ACS (600 mg/kg/day) by oral gavage for four weeks. Consumption of ACS remarkably suppressed the elevated total cholesterol (p < 0.01) and LDL-C (p < 0.001) induced by the high-cholesterol diet. Western blot results further indicated that the protein expression of PPARα in liver was upregulated in the ACS treatment group, and the results clearly demonstrated that ACS provides a beneficial effect on lowering HCD-associated detrimental changes.
Modern studies have shown that ACS has antioxidant, antitumor, liver protection, blood lipid regulation, platelet aggregation inhibition, blood pressure reduction, antifibrotic, and hemorheology index improvement functions.
Evidence strength: Rodent model only (one study, 600 mg/kg/day, 4 weeks). No published human clinical trials demonstrating cholesterol-lowering effects of ACS specifically.
Previous scientific studies have reported that SAC exhibits a number of therapeutic effects on chronic diseases such as cardiovascular diseases, diabetes mellitus, and cancers. SAC has been officially indexed in the Pharmacopoeia of the People's Republic of China due to its health-promoting and medical functions, including antidiabetic activity.
Astragalus membranaceus, A. mongholicus, and A. complanatus have been mainly used in folk medicine for their anti-inflammatory, immunostimulant, antioxidative, anti-cancer, antidiabetic, cardioprotective, hepatoprotective, and antiviral properties in recent years. The active constituents responsible for these effects were proved to be polysaccharides, saponins, and flavonoids.
Evidence strength: Predominantly in vitro and preclinical; much of the antidiabetic evidence from the broader Astragalus genus relates to A. membranaceus polysaccharides rather than specifically to A. complanatus. No human RCTs specifically testing ACS for diabetes have been identified.
ACS has been used traditionally to tonify yang, strengthen the kidney, and consolidate kidney qi, in relation to stabilizing the essence in conditions such as seminal emission, spermatorrhea, enuresis, frequent urination, leukorrhagia, and lumbar pain. In clinical settings, ACS serves as the main herb of the decoction Jin Suo Gu Jing Wan (Metal Lock Pill to Stabilize the Essence) or as an add-on therapy along with other Chinese medicine decoctions for treating sexual dysfunction such as spermatorrhea.
When treating erectile dysfunction with Chinese medicine, ACS is sometimes added into the formula for strengthening the yang, and patients have been reported to experience fewer side effects compared to SSRIs.
Evidence strength: Traditional use is well-documented. Modern clinical evidence for specific reproductive outcomes attributed to Astragalus complanatus alone is not available from identified published controlled trials. Most evidence comes from multi-herb TCM formula studies.
Flavonoids from Astragalus complanatus R. Br. (FAC) have demonstrated anticancer effects on many tumor cells. Studies were performed to evaluate the effects of FAC on human breast cell proliferation, apoptosis, and metastasis, as well as their active mechanisms. Proliferation of three breast cell lines was inhibited with FAC treatment in a dose-dependent manner, and survival time of nude mice with breast cancer cell inoculation was prolonged with increasing FAC dose.
The flavonoid component from the seeds of Astragalus complanatus (FAC) has hepatoprotective, anti-liver fibrosis, anti-tumor, and immune enhancement properties. Studies investigated in vitro the regulation effect of FAC on NK cell function and possible mechanism of action. The effect of FAC on the proliferation ability of NK-92 cells and the cytolysis of NK-92 cells to K562 and SMMC-7721 was measured by MTT assay and lactate dehydrogenase (LDH)-releasing assay.
Evidence strength: These studies are in vitro (cell lines) and in animal models. No controlled human clinical trial data have been identified for ACS specifically as an antitumor or immunomodulatory agent. All findings are preliminary.
The flavonoid fraction obtained from the seeds of Astragalus complanatus showed a significant radioprotective effect against damage induced by γ-irradiation in mice. The flavonoid fraction increased the survival rate of the experimental animals and facilitated recovery of the damaged organ, with the mechanism involving enhancement of immunity and blood-producing function. This activity could be explained by a reduction of DNA injury and mutation in vitro.
Evidence strength: Animal (murine) model only; no human data identified.
According to traditional Chinese medicine, ACS is considered efficacious in improving vision, liver functions, and kidney functions. ACS has the TCM function of nourishing the liver and brightening the eyes. This traditional claim has not been evaluated in controlled human trials.
Evidence strength: Traditional claim; no clinical trial evidence identified.
Dosages reported in identified scientific studies — given as stated in sources:
For the broader Astragalus genus (primarily A. membranaceus), it may be safe when used orally; taking up to 60 grams per day for as long as 4 months does not seem to cause adverse effects. However, a thorough safety evaluation has not been done. These figures relate to the Astragalus genus and predominantly to A. membranaceus; no equivalent standardized clinical dosage data specific to Astragalus complanatus seed has been formally established in human clinical guidelines.
Research suggests that there is insufficient scientific information to determine appropriate dosages of astragalus, which may depend on someone's age, health status, and other factors.
In a 90-day repeated-dose toxicity study administering a constant daily dose of 47 g of crude Astragalus drug per kilogram of body weight, no treatment-related mortality, clinical abnormalities, or gross/histopathological changes were observed. Hematological evaluations, clinical biochemical analyses, bone marrow cytology assessments, and spleen immune typing did not reveal any adverse changes. The high-dose administration did not exhibit significant toxic effects in Sprague–Dawley rats, thereby supporting its safety within a certain dose range. It should be noted that this study was conducted with A. membranaceus root extract rather than ACS seeds specifically.
A safety concern specific to ACS is the risk of misidentification or adulteration with related Astragalus species. Over 50 reviewed articles used an incorrect scientific name for the source plant. Seeds of some Astragalus species such as Astragalus sinicus L. and Astragalus adsurgens Pall. are sold as SAC in the market. Some other species, such as Astragalus mollissimus and Astragalus lentiginosus, contain the compound swainsonine, which can cause nerve damage and toxic selenium accumulation, leading to severe poisoning when consumed. Misuse of these species can cause unpredictable and dangerous consequences for health.
Because astragalus might worsen symptoms of autoimmune diseases, people with autoimmune diseases should avoid using astragalus. Additionally, astragalus may interact with medications that suppress the immune system.
Very high doses of astragalus may suppress the immune system and are not suitable for people with autoimmune diseases or those who are pregnant or nursing.
Little is known about whether it is safe to use astragalus during pregnancy or while breastfeeding.
Astragalus may interact with medications that suppress the immune system. Based on pharmacological properties documented for the Astragalus genus:
Astragalus belongs to the Fabaceae family, the same plant family as peanuts, soybeans, chickpeas, and lentils. People with a known allergy to legumes should consider the possibility of cross-reactivity with astragalus. Allergic reactions could range from mild skin irritation to more serious responses depending on sensitivity. This does not mean everyone with a peanut allergy will react to astragalus, but the shared plant family is worth noting.
Flat-stem milk-vetch is closely related to Astragalus membranaceus, another species more extensively studied and used for similar purposes. However, direct scientific evidence supporting the efficacy of Astragalus complanatus specifically is limited. Care should be taken not to assume that safety and efficacy data from A. membranaceus automatically apply to A. complanatus, as these are distinct species with different primary plant parts used (root vs. seed) and differing phytochemical profiles.
The body of published scientific research on flat-stem milk-vetch (Astragalus complanatus seed / Semen Astragali Complanati) is predominantly preclinical. Experimental studies, mostly in vitro and in animal models, have indicated that extracts from Astragalus complanatus may help regulate immune responses, reduce inflammation, and protect against oxidative stress. Some preliminary clinical studies have explored the effects of flat-stem milk-vetch extracts on immune modulation and liver health, suggesting potential benefits. However, the volume of well-designed human clinical trials remains limited. The existing evidence across all studied areas — anti-fibrotic, antihypertensive, lipid-lowering, antitumor, antidiabetic, and immunomodulatory — is characterized by: animal/in vitro models; small sample sizes where human studies exist; lack of multicenter randomized controlled trials; and frequent use as part of multi-herb TCM formulas rather than as a single agent, making it impossible to attribute effects to ACS alone in those contexts. Previous scientific studies have reported that SAC exhibits a number of therapeutic effects on chronic diseases such as cardiovascular diseases, diabetes mellitus, and cancers, but robust clinical translation remains incomplete. All pharmacological claims require further investigation through adequately powered, controlled human clinical trials before definitive conclusions can be drawn.
Health conditions that Flat-stem milk-vetch may help support.
Body systems that Flat-stem milk-vetch may help support.
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