Ingredients5-Alpha-furostan-12-one-3β,22,26-triol (also rendered as (25R)-5α-furostan-12-one-3β,22α,26-triol when the stereochemistry at C-25 is specified) is the steroidal aglycone core — the so-called sapogenin — shared by a family of furostanol-type steroidal saponins. In the primary literature it appears embedded within larger glycosidic molecules: the carbohydrate chains attached at the C-3 and C-26 hydroxyl positions of the aglycone distinguish individual saponin species from one another, and the aglycone itself is rarely encountered free in plant tissue. As a dietary-supplement ingredient label designation, the name "5-alpha-furostan-12-one-3 beta, 22, 26-triol" identifies either the free aglycone or, more commonly in commercial context, extracts of plants whose furostanol saponin complement includes compounds carrying this aglycone scaffold.
Structurally, the compound belongs to the furostanol (furostane) class of steroidal saponins. Steroid saponins consist of two groups corresponding to spirostanol (e.g., dioscin) and furostanol (e.g., protodioscin) aglycones. The furostane skeleton is a 27-carbon, tetracyclic-plus-bicyclic ring system: rings A–D form the familiar steroid nucleus, ring E is a tetrahydrofuran (furanyl) ring, and ring F is an open-chain appendage terminating at C-26 — in contrast to spirostanol saponins, where ring F is closed into a spiroketal. The presence of a ketone at position C-12, in addition to hydroxyl groups at C-3β, C-22, and C-26, gives this particular aglycone its characteristic triol-ketone profile. The designation "5α" refers to the trans A/B ring junction, a structural feature that distinguishes these compounds from 5β (cis) congeners.
The furostanol saponins bearing the 5α-furostan-12-one-3β,22,26-triol aglycone have been characterised primarily from Tribulus terrestris L. (family Zygophyllaceae). Two new steroidal saponins were isolated from the fruits of Tribulus terrestris, their structures assigned by spectroscopic analysis as 26-O-β-D-glucopyranosyl-(25R)-5α-furostane-12-one-3β,22α,26-triol-3-O-β-D-glucopyranosyl(1→4)-β-D-galactopyranoside (1) and 26-O-β-D-glucopyranosyl-25(R)-5α-furostan-12-one-3β,22α,26-triol-3-O-α-L-rhamnopyranosyl-(1→2)-O-[β-D-glucopyranosyl-(1→4)]-β-D-galactopyranoside (2).
Beyond T. terrestris, furostanol saponins with related structural backbones (though not always the 12-one-3β,22,26-triol aglycone specifically) have been reported from other plant genera. Furostanols, a class of steroidal saponins, have a long-standing history in traditional medicine, primarily derived from plants such as fenugreek (Trigonella foenum-graecum), tribulus (Tribulus terrestris), and wild yam (Dioscorea species). Related 5α-furostanol saponins have additionally been isolated from Yucca species, including Yucca schidigera Roezl. trunk, from which eight steroidal saponins were isolated including novel furostanol glycosides, and from flowers of Yucca elephantipes, from which a novel compound characterized as (25R)-26-O-β-D-Glcp-5α-furostan-3β,22α,26-triol was isolated. Furostanol saponins bearing the same core oxidation pattern have also been reported from the Asparagus and Capsicum genera.
Within T. terrestris, the phytochemical diversity of furostanol saponins is substantial. To date, a wide variety of steroidal saponins have been isolated from T. terrestris, among them 58 kinds of spirostane saponins and 50 kinds of furostane saponins; steroidal saponins such as protodioscin and protogracillin are thought to confer unique biological activities. The 12-one-3β,22,26-triol aglycone-containing saponins represent a subset of this furostanol complement that has attracted specific phytochemical attention.
Tribulus terrestris L. is a perennial plant widely distributed around the world, especially in subtropical areas. It is native to southeastern and Mediterranean Europe, temperate and tropical Asia and Africa, and northern Australia. Fructus Tribuli (FT), the dried mature fruit of Tribulus terrestris L., is extremely rich in a variety of natural compounds such as steroidal saponins, flavonoids, alkaloids, and lignin amides.
In commerce, this compound is encountered almost exclusively as part of standardised extracts of T. terrestris, most frequently the dried fruit. The dietary supplement ingredient Tribulus is prepared from the leaves, root, and fruit of the Tribulus terrestris L. plant, which contains numerous chemical compounds, including steroidal saponins (plant steroids). Tribulus is available in tablets and capsules of 250 and 500 mg, and the usual daily dose is 250 to 750 mg daily. Commercial products are typically standardised to a minimum furostanol saponin content; for example, each Tribestan film-coated tablet contains the active substance Tribulus terrestris, herba extractum siccum (35–45:1) 250 mg which is standardised to furostanol saponins (not less than 112.5 mg).
Worldwide, there are many pharmaceutical preparations and herbal supplements containing extracts standardised in steroidal saponins. Since the early 1980s, TT extract has been an attractive unconventional medicine product used in Western countries as a testosterone booster, libido enhancer, and adaptogenic aid for healthy, physically active men.
Because the 5α-furostan-12-one-3β,22,26-triol aglycone is a component of glycosylated saponins rather than an independent, freely occurring molecule in most plant preparations, it is important to note that consumers ingesting standardised T. terrestris extracts are primarily consuming the intact glycoside forms; the aglycone designation on a supplement label thus functions as a structural identifier for the saponin class rather than a claim that free sapogenin is present.
Tribulus terrestris has been used for thousands of years as a well-known traditional medicine in China and is listed as a superior herbal medicine in the oldest extant Chinese pharmaceutical monograph "Shen Nong Ben Cao Jing." Its dried fruit, named "Jili" in Chinese, has been used as a traditional Chinese medicine (TCM) for the treatment of edema, abdominal distention, emission, morbid leucorrhea, and vitiligo. Its fruits have been used in traditional Chinese medicine for treatment of eye problems, edema, abdominal distention, emission, morbid leucorrhea, sexual dysfunction, and veiling. Additionally, T. terrestris (the fruit or the whole plant) can not only act as an aphrodisiac tonic and an antibacterial agent, but is also used for the treatment of cardiovascular diseases.
The TCM preparation tradition involved using the dried, mature fruit (Fructus Tribuli) either as a decoction or in powdered form as part of compound herbal formulas. Steroidal saponins from T. terrestris have been commercially available as active compounds in traditional Chinese medicine formulations, such as "Xin-nao-shutong," which has been used for the treatment of cardiovascular disease. According to traditional Chinese medicine theory, Fructus Tribuli has low toxicity, which can be reduced by stir-frying.
Tribulus terrestris L. has been used since ancient times in traditional Indian medicine (Ayurveda), and the traditional medicine of southeastern Europe for the treatment of different conditions. Commonly known as Gokshur or Gokharu or puncture vine, it has been used for a long time in both the Indian and Chinese systems of medicine for treatment of various kinds of diseases. In the Ayurvedic tradition, Gokshura preparations (typically made from the whole plant or fruit) were employed for urinary tract conditions, reproductive health support, and as a rasayana (rejuvenating) tonic. It is recommended in Ayurveda for the treatment of angina pectoris and other cardiac complications.
Tribulus terrestris L. (TT) is an annual plant of the family Zygophyllaceae that has been used for generations to energize, vitalize, and improve sexual function and physical performance in men. The fruits and roots of TT have been used as a folk medicine for thousands of years in China, India, Sudan, and Pakistan. It has also been used as a medicine in India, South Africa, and Japan.
In southeastern Europe, particularly Bulgaria, the plant attracted attention from Soviet-era researchers and athletes. In Europe, Tribulus terrestris has been used to address urinary and reproductive concerns and as a mood enhancer. Soviet men treasured this herb as a tonic and for its ability to stimulate hormone production, and based on this effect it became a popular supplement for bodybuilders and athletes. The Bulgarian pharmaceutical preparation Tribestan® (Sopharma), still commercially available, traces its development to this Soviet and Eastern European tradition.
The term "5-alpha-furostan-12-one-3β,22,26-triol" designates the aglycone (sapogenin) backbone that is common to at least two individually characterised saponin species isolated from T. terrestris fruits. When attached to different sugar chains, the same aglycone generates structurally distinct glycosides with potentially different biological profiles. Tribulus terrestris is a rich source of furostanol and spirostanol saponins and flavonoids.
The furostanol and spirostanol series are biochemically inter-convertible. Both furostanol and spirostanol types of steroidal saponins are derived from either the 30-carbon linear precursor 2,3-oxidosqualene (cycloartenol pathway) or 22,26-dihydroxycholesterol (cholesterol pathway), but during the synthesis of their steroidal aglycone loss of three methyl groups results in a 27-carbon backbone. Conversion of furostanol saponin into spirostanol form and vice versa is catalysed by furostanol glycoside 26-O-β-glucosidase (F26G) and UGT glucosyltransferase enzyme, respectively. Steroidal saponins are natural surfactants with various biological activities; a β-glucosidase is involved in the hydrolytic conversion from furostanol glycosides to spirostanol glycosides.
Various parts of T. terrestris contain a variety of chemical constituents which are medicinally important, such as flavonoids, flavonol glycosides, steroidal saponins, and alkaloids. The main biologically active compounds in Tribulus terrestris are furostanol-type saponins, particularly protodioscin, which is considered the most potent component. Protodioscin is the main saponin found in the extracts made from T. terrestris plant's air-dried aerial portions, which mainly include steroidal glycosides. The 5α-furostan-12-one-3β,22,26-triol aglycone saponins are thus one subset among numerous co-occurring furostanol and spirostanol compounds; biological effects observed in whole-extract studies cannot be attributed to any single saponin species without further isolate-specific investigation.
Neuroendocrine axis modulation: The steroidal saponins (gitonin, protodioscin, and tribulosaponins A and B) present in T. terrestris have an effect on androgen receptors in the brain, causing an underestimation of sex hormone levels, which causes the posterior pituitary gland to secrete more LH and, as a consequence, increased testosterone synthesis in the testes. Protodioscin has been suggested to act on the hypothalamus to stimulate LH and FSH secretion that further improves testosterone production by the Leydig cells.
Neurosteroid activity: Saponins from T. terrestris also act directly as a neurosteroid, increasing dehydroepiandrosterone levels, which may exert an antagonistic effect on gamma aminobutyric acid (GABA) and thereby enhance sexual function.
Adaptogenic / anti-stress properties: Studies suggest that saponins may have adaptogenic effects, meaning they help the body adapt to stress and maintain homeostasis.
Phosphodiesterase inhibition: Calcium ion inhibition of the enzyme phosphodiesterase may explain the impact of T. terrestris saponins on sperm motility by preventing the degradation of cAMP, and aphrodisiac activity by preventing the degradation of cGMP.
Antimicrobial and anti-inflammatory surface activity: Steroidal saponins are responsible for the antimicrobial and anti-inflammatory properties of TT. Saponins in general disrupt microbial membranes through cholesterol complexation, an activity shared with other amphipathic steroidal surfactants.
It must be emphasised that most mechanistic data derive from in vitro or animal studies using whole extracts or the principal saponin protodioscin. The specific mechanism attributable to the 12-one-3β,22,26-triol aglycone-containing saponins in isolation has not been independently established in published human clinical research.
This is the area with the largest body of human clinical investigation for T. terrestris extracts standardised to furostanol saponins. The evidence, however, is predominantly mixed and context-dependent.
Despite the proposed effects of TT supplementation as a testosterone booster through different mechanisms, 80% of the studies analysed in one systematic review did not report significant changes in the androgen profile following TT supplementation (400–750 mg/d for 2–3 months). Only two studies in that review exclusively enrolled subjects with low testosterone levels (<350 ng/mL) and observed effects of TT supplementation as a testosterone booster; in both studies, subjects received 3 capsules daily (750 mg) of TT (Trib Gold, origin Bulgaria, 250 mg of TT and a minimum of 45% of saponins per capsule) over 3 months.
One specific trial reported a quantified effect: through a randomised, single-blind, placebo-controlled trial, 70 patients with late-onset hypogonadism reported a ~58 ng/mL (27%) increase in mean total testosterone levels (from ~215 to ~273 ng/dL, p < 0.001) in the group receiving TT.
However, most studies conducted on healthy men have not found any significant changes in either LH or testosterone levels. Studies in animal models suggested that tribulus increases testosterone levels in males and estrogen levels in females, but these hormonal effects have not been reproduced consistently in humans.
Regarding geographic variation of the plant material: the literature data reveal differences in the saponins content and composition of TT growing in different geographic regions of the world, and it has been reported that the high content of furostanol saponins of the diosgenin type is a characteristic feature of TT from Bulgaria. Such variations in the saponin content and composition of TT could explain its different reported bioactivities in different regions; based on the origin of the herbal medicine used and the fact that the preparation is standardised with respect to furostanol saponins calculated against protodioscin, results of trials using Bulgarian-origin TT should not be extrapolated directly to other TT preparations obtained from other regions.
A pivotal prospective, randomised, double-blind, placebo-controlled trial examined the efficacy and safety of furostanol-standardised TT in male sexual dysfunction. The trial enrolled 180 males aged 18 to 65 years with mild or moderate erectile dysfunction (ED) and with or without hypoactive sexual desire disorder (HSDD), randomised 1:1 to treatment or placebo groups. The TT group received 2 tablets (500 mg) Tribestan orally three times daily after meals for 12 weeks; each tablet contains the active substance TT herba extractum siccum 250 mg with a content of furostanol saponins not less than 112.5 mg.
Patients affected by mild to moderate ED and/or low libido may significantly benefit from oral therapy with TT, without any significant changes in biochemistry laboratory test results. Nonetheless, the overall body of evidence remains limited. In controlled trials, improvements in sexual function were no greater with Tribulus terrestris extracts than with placebo. These conflicting findings across trials are likely attributable to differences in extract standardisation, geographic origin of plant material, patient population, and outcome measures used.
A meta-analysis-level evaluation found: a mild effect of TT on testosterone, FSH, and LH levels, suggesting that TT may provide such benefits in infertility or adverse exposures but not under normal conditions.
Results of human and animal clinical trials support a FSH-stimulating prescription; in one study, 750 mg of active furostanol (TLSE) per day for 5 days was given to women and was shown to increase FSH and estradiol compared with baseline. Evidence in this domain is sparse and preliminary; no large-scale, adequately-powered, randomised controlled trials have been published specifically evaluating the 12-one-3β,22,26-triol aglycone saponins in female fertility outcomes.
TT is used in traditional Chinese medicine, Ayurvedic medicine, and sports nutrition to improve health and performance; however, no conclusive evidence exists about the potential beneficial effects of TT on sport and health biomarkers in physically active adults. High-dose administration in athletes has raised immunological concerns: it has been reported that 1,875 mg of TT for 20 days induces a change in leukogram transformed into granulocytes with a substantial decrease in lymphocytes and significant increases of neutrophils, basophils, and eosinophils in endurance athletes; the dose and/or the high percentage of steroid saponins in TT supplementation could be responsible for immunosuppression, which could be like that of corticosteroids.
The broader conclusion from systematic review-level evidence is that furostanol-standardised TT supplements do not reliably improve body composition, strength, or power output in healthy athletes with normal hormonal profiles, a finding consistent with the lack of testosterone elevation seen in this population.
TT plays an important role in the treatment of cardiovascular disease with anti-myocardial ischaemia and myocardial ischaemia–reperfusion injury; steroidal saponins from TT have a protective effect on myocardial ischaemia–reperfusion injury. These findings are based on preclinical (animal and in vitro) data; robust human cardiovascular trial data specifically using the 12-one-3β,22,26-triol saponins are not available in the published literature reviewed.
Furostanol saponins from the same family have demonstrated cytotoxic activity against human cancer cell lines in vitro, though not specifically the 12-one-3β,22,26-triol aglycone-containing saponins in isolation. New furostanol saponins isolated from dry fruits of T. terrestris were evaluated for inhibitory effects on tumour cells, and compounds showed potential anti-tumour activity. These are in vitro data only; no human oncology trial evidence exists for this compound class.
Isolated furostanol saponins have shown higher antimicrobial activity in in vitro assays. Again, this is limited to laboratory-based studies; no clinical antimicrobial trial data were identified in the sources reviewed for this article.
Based on the evidence surveyed, the following body systems and health areas are associated with the furostanol saponins sharing the 5α-furostan-12-one-3β,22,26-triol aglycone scaffold, primarily through data from whole T. terrestris extracts:
A comprehensive phytopharmacological overview credits T. terrestris with diuretic, aphrodisiac, antiurolithic, immunomodulatory, antidiabetic, absorption-enhancing, hypolipidaemic, cardiotonic, central nervous system, hepatoprotective, anti-inflammatory, analgesic, antispasmodic, anticancer, antibacterial, anthelmintic, larvicidal, and anticariogenic activities. It must be emphasised that not all of these activities have been demonstrated at the clinical (human) level; many rest on animal and in vitro models.
Clinical studies have used a range of standardised oral preparations. The following dosages are reported directly from published studies and sources; they describe what was studied, not what is recommended:
Short-term studies (up to 3 months) have reported few adverse effects, such as stomach cramps and nausea. Due to the saponin content of the plant, gastrointestinal disturbances may be seen in sensitive individuals. Another reported rare side effect is gynaecomastia; additionally, excitation, menorrhagia, and insomnia were reported in a clinical study.
A few cases of severe liver and renal (kidney) damage have been reported after individuals consumed supplements containing Tribulus. In one published case, a healthy 30-year-old male bodybuilder developed severe hyperbilirubinemia followed by acute renal failure and bile-containing casts in the tubules associated with the ingestion of tribulus extract tablets, once daily for "a few months." In another case, a 28-year-old man who consumed large quantities of tribulus extract for its antiurolithiatic properties developed neuro-, hepatic, and renal toxicity suggestive of acute tubular necrosis, hypertension, seizures, and markedly elevated serum aminotransferases (>40× upper limit of normal).
A case of hepatic failure in a female patient was also documented: the patient used Tribulus terrestris every day for about 2–3 months, which led to generalised icterus and abdominal pain; her liver function tests showed elevated ALT, AST, and bilirubin, and abnormal PT, PTT, INR; steroidal saponins are proposed as possibly producing deposition of crystalloid materials causing liver failure.
Tribulus terrestris has not been reported to cause serum enzyme elevations in persons taking the herbal extract, but prospective studies with regular monitoring of liver tests have not been done. Isolated case reports of renal injury with serum aminotransferase elevations have been published but may have represented instances of ischaemic or anabolic steroid-induced liver and kidney injury rather than direct hepatotoxicity of the extract. Clinically apparent liver injury from Tribulus in humans has not been convincingly shown.
The plant itself is known to be toxic to rats and sheep after ingesting large amounts; effects include damage to the heart, liver, and kidneys. The Tribulus terrestris plant is known to be toxic to grazing animals and can cause distinctive liver injury known as "geeldikkop" or hepatogenous photosensitivity; histology of the liver from sheep dying after feeding upon the leaves demonstrates crystals in bile ducts and renal tubules. The steroidal saponin diosgenin is thought to be responsible for hepatotoxic effects associated with tribulus.
According to TCM theory, Fructus Tribuli has low toxicity, which can be reduced by stir-frying; prior studies showed that hepatorenal toxicity of rats treated with crude Fructus Tribuli powders continuously for 12 weeks was higher than that of rats treated with stir-fried powders.
Research evaluating the safety of Tribulus in humans is limited; more research is needed to determine the safety of Tribulus as a dietary supplement ingredient, especially long term and in varying doses.
Use of Tribulus terrestris with antihypertensive drugs may increase the possibility of hypotension. Tribulus can also increase the blood sugar-lowering effects of hypoglycaemia drugs.
An important quality and safety variable is the substantial geographic variation in saponin composition. Literature data reveal differences in the saponins content and composition of TT growing in different geographic regions of the world; the high content of furostanol saponins of the diosgenin type is a characteristic feature of TT from Bulgaria. This variability means that the specific concentrations of 5α-furostan-12-one-3β,22,26-triol aglycone-bearing saponins will differ substantially across commercial products, making cross-product dosage comparisons unreliable.
The evidence base for the biological activities of 5α-furostan-12-one-3β,22,26-triol and its glycosides must be assessed critically:
Health conditions that 5-alpha-furostan-12-one-3 beta, 22, 26-triol may help support.
Body systems that 5-alpha-furostan-12-one-3 beta, 22, 26-triol may help support.
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