IngredientsThe compound commonly designated in supplement labeling as 5α-furostan-12-one-3β,22,26-triol (also rendered as 26-diol, 5 alpha-furostan-12-one-3 beta, 22, 26-triol) belongs to the furostanol class of steroidal saponin aglycones. In the peer-reviewed phytochemical literature it appears almost exclusively as the aglycone moiety of fully glycosylated saponin molecules, such as the compound structurally characterized by Yan et al. (1996) as 26-O-β-D-glucopyranosyl-3-O-[{β-D-xylopyranosyl(1→3)}-β-D-galactopyranosyl(1→2)-β-D-glucopyranosyl(1→4)-β-D-glucopyranosyl]-5α-furostan-12-one-3β,22,26-triol. This structure was isolated from the aerial parts of Tribulus terrestris L., established on the basis of chemical and spectroscopic evidence, especially 2D NMR spectroscopic techniques.
Related glycosidic forms carrying the same aglycone core have also been documented; for example, two new steroidal saponins were isolated from the fruits of Tribulus terrestris, with structures assigned 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 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. Additionally, two furostanol glycosides named tribufurosides I and J were isolated from the fruits of Tribulus terrestris L., with one structure established as 26-O-β-D-glucopyranosyl-(25S)-5α-furost-12-one-2α,3β,22α,26-tetraol-3-O-β-D-glucopyranosyl(1→2)-β-D-glucopyranosyl(1→4)-β-D-galactopyranoside and another as 26-O-β-D-glucopyranosyl-(25R)-5α-furost-20(22)-en-12-one-2α,3β,26-triol-3-O-β-D-glucopyranosyl(1→4)-β-D-galactopyranoside.
The compound name "5α-furostan-12-one-3β,22,26-triol" thus specifies: a furostane (furostanol) tetracyclic steroidal skeleton with a 5α-hydrogen configuration (A/B trans ring junction), a ketone function at carbon-12, and hydroxyl groups at positions C-3β, C-22, and C-26. In naturally occurring glycoside forms, the C-26 hydroxyl typically participates in a glycosidic linkage with a glucose unit. Furostan saponins of natural occurrence are bidesmosides in which a glucose monosaccharide is attached at the 26-OH group of the aglycone, and an oligosaccharide chain is usually connected at 3-OH.
The compound belongs to the furostanol subdivision of steroidal saponins. Steroid glycosides are divided into spirostanol and furostanol saponins. The spirostane skeleton consists of a five-ring structure with an additional sixth ring containing C22–26; meanwhile, the furostane skeleton consists of a five-ring structure wherein C22–26 is an open chain and C26 possesses a hydroxyl group which is often engaged in a glycosidic linkage. The 12-oxo function distinguishes this particular triol from simpler furostanols, and is characteristic of several Tribulus-derived saponins. From the viewpoint of biosynthesis, furostan-type saponins are thought to be the precursors of the corresponding spirostan-type saponins in plants.
The primary and most thoroughly documented botanical source is Tribulus terrestris L. (family Zygophyllaceae), commonly known as puncture vine, caltrop, or bindii. Tribulus terrestris L. is an annual plant found around the world. The 5α-furostan-12-one-3β,22,26-triol aglycone core has been repeatedly characterized from the plant's fruits, aerial parts, and roots across multiple independent phytochemical studies.
Furostanol saponins sharing the same furostan-12-one core pattern have additionally been reported from other plants such as fenugreek (Trigonella foenum-graecum) and certain species of the Dioscorea (yam) genus. The three major sources of furostanolic saponins are Tribulus terrestris, Dioscorea deltoidea, and fenugreek.
Protodioscin — a related and frequently co-occurring furostanol glycoside — is a naturally occurring steroidal saponin classified as a furostanol glycoside found in various plant species including Tribulus terrestris, Dioscorea species (such as Dioscorea nipponica and Dioscorea collettii), fenugreek (Trigonella foenum-graecum), and Trillium govanianum.
In commerce, 5α-furostan-12-one-3β,22,26-triol is not typically sold as a purified isolate; rather, it appears as one constituent within standardized extracts of Tribulus terrestris, fenugreek seed, or Dioscorea rhizome. The extract obtained from the aerial parts of the dry plant contains furostanol-type steroidal glycosides (saponins), of which the predominant active component is protodioscin (PTN), which represents 45% of the extract. Some steroidal saponins have previously been isolated from this plant. Many pharmaceutical preparations and food supplements with these saponins as the active compound have been commercially available.
Commercial supplement labels frequently identify this specific saponin alongside protodioscin within blended extracts standardized to total saponin content. One example lists the compound as part of a Puncture Vine (whole plant) extract standardized to 40% saponins, including 25-D-spirosta-3, 5α-furost-20(22)-en-12-one-3β,26-diol, 5α-furostan-12-one-3β,22,26-triol, and protodioscin. Preparations include oral capsules, tablets, and standardized dry extracts. Tribestan® film-coated tablets, one commercially available preparation, contain Tribulus terrestris herba extractum siccum (35–45:1) 250 mg standardized to furostanol saponins (not less than 112.5 mg).
Examples of pharmaceutical preparations include "tribusaponins" and "Xin-nao-shu-tong," which have been used for the treatment of cardiovascular disease.
Tribulus terrestris, as the primary source of 5α-furostan-12-one-3β,22,26-triol-containing preparations, has an extensive history in Ayurvedic medicine, where it is known as Gokshura (Sanskrit: "cow's hoof"). The plant is used in Ayurvedic, Yunani, and Chinese traditional medicines, where it is known as Gokshura (Sanskrit), Khar-e-Khasak Khur, and Bai Ji Li respectively. In India and China, the medicinal use of this herb is traced back 5,000 years.
Tribulus terrestris has been used for centuries in Ayurveda to treat impotence, venereal diseases, and sexual debility. According to the Canadian government's Natural Health Products monograph for this plant, it was traditionally used in Ayurveda as a diuretic (Mutrala) and as Vrsya (aphrodisiac) for men. The same monograph notes it was traditionally used in Ayurveda to help relieve Arsa (hemorrhoids) and Mutrakrcchra (difficult/painful urination).
In Ayurvedic pharmacology, Tribulus terrestris is used as a powder form of the aerial parts, particularly the fruits, for healthy flow of urine and to soothe the urinary membrane. It acts as a tonic for the healthy production of sperm and helps in rejuvenating the uterus and other organs responsible for pregnancy in females. In Ayurveda, Tribulus has been used for centuries to support kidney health, urinary function, and sexual health. It is considered a rasayana (rejuvenating herb) and is used to support strength, vitality, and longevity.
The fruits of Tribulus terrestris have been used in Traditional Chinese Medicine for the treatment of eye problems, edema, abdominal distention, emission, morbid leucorrhea, sexual dysfunction, and veiling. In TCM, the plant was used for headache and dizziness, and related conditions. In TCM, Tribulus was used as a tonic for improving blood circulation, supporting kidney function, and enhancing sexual energy. It was considered beneficial for menstrual irregularities, low libido, and as a general restorative herb.
In Bulgaria, the plant is used as a folk medicine for treating impotence. It has also been used as a medicine in India, South Africa, and Japan. Traditional preparations have taken many forms. Ayurvedic practice employed the powdered dried fruit; folk preparations in Eastern Europe have included decoctions; and standardized Bulgarian extracts (principally the Tribestan® preparation) emerged in the latter 20th century as a commercial distillation of these traditions.
Ancient Ayurvedic and Traditional Chinese Medicine texts mention the use of furostanol-rich herbs for enhancing vitality, supporting reproductive health, and promoting general well-being. For example, fenugreek seeds, abundant in furostanol saponins, have been utilized to support lactation, improve digestion, and manage blood sugar levels.
Tribulus terrestris, a plant of the Zygophyllaceae family, has been used for a long time in both Indian and Chinese traditional medicine, and its different parts contain a variety of active constituents, such as flavonoids, flavonol glycosides, steroidal saponins, and alkaloids. Over 70 different chemical compounds have been identified in Tribulus terrestris, some of which are the subject of medical research concerning antioxidant activity, antibacterial activity, antihyperglycemic effect, anti-inflammatory properties, and beneficial effects on the central nervous system.
Within this phytochemical profile, furostanol saponins are prominent. Steroidal saponins and flavonoids are considered the most important metabolites with multiple bioactivities. The steroidal saponins (including gitonin, protodioscin, and tribulosaponins A and B) present in Tribulus 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.
The 5α-furostan-12-one-3β,22,26-triol aglycone is structurally defined by two principal features: the open-chain furostane ring system (contrasting with the closed spirostane ring of related saponins) and a ketone (oxo function) at C-12. Several named saponins documented in the peer-reviewed literature share this aglycone core. Among these are compounds including 26-O-β-D-glucopyranosyl-(25R)-5α-furostan-3β,22α,26-triol-12-one (designated terrestrinin F), isolated in a series of steroidal saponins from Tribulus terrestris.
An additional related glycoside carrying this aglycone pattern was confirmed by PMC-published research: a new furostanol glycoside was isolated from the fruits of Tribulus terrestris L. with a structure established as 26-O-β-D-glucopyranosyl-(25S)-5α-furostane-20(22)-en-12-one-3β,26-diol-3-O-α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→4)]-β-D-galactopyranoside on the basis of 1D and 2D-NMR techniques, including COSY, HMBC, and HMQC correlations.
Protodioscin is the best-characterized furostanol glycoside co-occurring with 5α-furostan-12-one-3β,22,26-triol in commercial extracts. Protodioscin is a naturally occurring steroidal saponin classified as a furostanol glycoside with the molecular formula C₅₁H₈₄O₂₂, found in Tribulus terrestris, Dioscorea species, fenugreek (Trigonella foenum-graecum), and Trillium govanianum. Chemically, protodioscin features a furostanol aglycone backbone linked to a trisaccharide chain at the 3-OH position and a glucose monosaccharide at the 26-OH group. It is a major bioactive constituent in Tribulus terrestris, where its concentration can reach up to 1,530 mg/100 g in aerial parts, varying by plant part, geographic origin, and extraction method.
Geographic origin of the plant significantly influences the saponin profile. Protodioscin is present in Tribulus harvested in Bulgaria, Turkey, Greece, Macedonia, Iran, and Serbia, while Tribulus from Vietnam and India contains no protodioscin at all.
In the steroidal saponin biosynthesis pathway, 22R-OH furostanol (22R-OH-Fu) is a key intermediate, and a 26-O-glycosyltransferase (F26GT) or 26-O-β-glucosidase (F26G) may participate in glycosyl modification and removal of the C26-O sugar group to determine whether spirostanol/isospirostanol steroids or furostanol saponins are synthesized. Furostanol saponins (e.g., protodioscin) result from glycosylation modification at C3-OH and/or C26-OH of 22R-OH-Fu with the opening of the F ring.
The most extensively discussed mechanism for furostanol saponins from Tribulus terrestris concerns the modulation of the hypothalamic–pituitary–gonadal axis. The steroidal saponins present in Tribulus 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 luteinizing hormone (LH) and, as a consequence, increased testosterone synthesis in the testes. Additionally, protodioscin in particular is believed to increase the conversion of testosterone to dihydrotestosterone, which promotes red blood cell production and muscle development.
Protodioscin has been suggested to act on the hypothalamus to stimulate LH and FSH secretion, which further improves testosterone production by the Leydig cells. The hydrolyzed saponins are transformed into steroidal sapogenins, which have antispasmodic and natriuretic properties, and increase the production of luteinizing hormone (LH), testosterone, estrogen, and other steroids.
Saponins from Tribulus are known to increase nitric oxide (NO) activity. This mechanism has been invoked to explain the plant's reported proerectile and cardiovascular effects. Nitric oxide-mediated vasodilation in corpus cavernosum tissue has been documented in animal models.
Calcium inhibits the enzyme phosphodiesterase, which may explain furostanol saponins' impact on sperm motility by preventing the degradation of cAMP, and their aphrodisiac activity by preventing the degradation of cGMP. This mechanism shares partial overlap with the mechanism of pharmacological PDE5 inhibitors used in erectile dysfunction therapy.
Previous research has revealed steroidal saponins possess various pharmacological activities, such as antifungal, hypocholesterolemic, antimitotic, and cAMP phosphodiesterase inhibitory effects. Tribulus terrestris has been studied for its multiple therapeutic effects, including immunomodulatory, aphrodisiac, anti-urolithic, absorption-enhancing, cardioprotective, antidiabetic, anti-inflammatory, hypolipidemic, neuroprotective, anticancer, and analgesic properties.
At the molecular level, furostanol saponins including protodioscin have been shown in cell-based (in vitro) studies to modulate cancer cell signaling pathways. Protodioscin promotes the expression of cleaved-PARP and cleaved-caspase 3 while decreasing E-cadherin levels. Saponins exert antitumor effects by targeting the NF-κB, PI3K–Akt–mTOR, MAPK, Wnt–β-catenin, JAK-STAT3, AMPK, p53, and EGFR signaling pathways. These observations are derived from cell culture and animal experiments and have not yet been translated to clinical outcomes.
Furostanol saponins isolated from the dry fruits of Tribulus terrestris, including compounds structurally related to the 5α-furostan-12-one-3β,22,26-triol core, showed potential anti-tumour activity in inhibitory effects evaluated on tumor cells.
The most extensive body of clinical literature for furostanol-standardized Tribulus terrestris preparations concerns sexual function. Patients affected by mild to moderate erectile dysfunction and/or low libido may significantly benefit from oral therapy with Tribulus terrestris, without any significant changes in biochemistry laboratory test results. Based on the origin of the herbal medicine used and the fact that the preparation is standardized with respect to furostanol saponins (calculated against protodioscin), the results of this trial should not be extrapolated directly to other preparations obtained from other regions.
The pivotal clinical trial in this area was a prospective, randomized, double-blind, placebo-controlled study using the Bulgarian Tribestan® preparation. Each Tribestan film-coated tablet contains Tribulus terrestris herba extractum siccum (35–45:1) 250 mg standardized to furostanol saponins (not less than 112.5 mg). Each patient received orally 3×2 film-coated tablets daily after meals during the 12-week treatment period. At the end of each month, sexual function including erectile dysfunction was assessed by the International Index of Erectile Function (IIEF) Questionnaire and Global Efficacy Question (GEQ). The primary outcome measure was the change in IIEF score after 12 weeks of treatment.
A systematic review of clinical trials on this topic found mixed but generally limited evidence. After searching the literature, 52 studies were selected for full-text reading and 10 were eligible, comprising 9 clinical trials and 1 quasi-experimental study. The Jadad score revealed low methodological quality for 50% of the studies. The studies involved 15 to 172 participants (total = 483) aged between 16 and 70 years with different health conditions.
A meta-analysis examining fertility and aphrodisiac effects concluded: while protodioscin has been suggested to act on the hypothalamus to stimulate LH and FSH secretion, improving testosterone production by Leydig cells, a mild effect of TT on testosterone, FSH, and LH levels was found, suggesting that TT may provide benefits in infertility or in adverse exposures but not under normal conditions.
Animal and open-label data in female subjects are also reported. In one trial measuring female sexual function, there was a significant improvement (p < 0.001) in the domains of vaginal lubrication, genital sensation, and ability to reach orgasm. There was no significant difference in adverse effects between the two groups. After 90 days of treatment, Tribulus terrestris was found to be effective in treating sexual problems among menopausal women at the doses used.
Strength of evidence: Preliminary to moderate. Results from well-controlled RCTs with standardized furostanol extracts are promising for mild to moderate erectile dysfunction and female sexual function, but overall trial sample sizes remain small and methodological quality is variable. Effects on testosterone in healthy men remain unconfirmed.
The widely claimed testosterone-boosting effect of furostanol-containing Tribulus terrestris extracts is one of the most extensively debated claims in the supplement literature. Tribulus has been reported to increase libido and serum testosterone in rat models of sexual dysfunction; despite the promising nature of these animal studies, a systematic review reported that although animal models have shown increased serum testosterone, no increase in testosterone was observed in men.
A randomized, single-blind, placebo-controlled study involving 30 healthy CrossFit®-trained males found: a total of 30 healthy CrossFit®-trained males were randomly allocated to receive either 770 mg of TT supplementation or a placebo daily for 6 weeks. There were no significant group × time interactions for the outcomes of the study except for testosterone levels and bench press performance (p < 0.05).
Some studies indicate that TT supplementation modulates androgen profile through an increase in serum testosterone levels and the testosterone/estradiol ratio. However, the meta-analytic evidence is more conservative: TT resulted in nonsignificant increases in testosterone and LH, and a nonsignificant decrease in FSH.
Strength of evidence: Weak to inconsistent in humans. Animal data consistently show androgenic effects; human RCT data are mixed, with most well-controlled trials in healthy men failing to demonstrate significant testosterone elevation.
Meta-analyses were conducted to evaluate the quantitative impact of TT on various fertility parameters. In humans, the pooled analysis on 133 subjects showed significant improvements in sperm concentration (SDM = 0.624, 95% CI = 0.13 to 1.117, p = 0.013) and sperm motility (SDM = 0.742, 95% CI = 0.331 to 1.152, p = 0.001).
Hemalatha and Rajeswari and Yin et al. reported an increase in body mass, reproductive organ mass, and physical strength due to the application of butanol extracts of TT fruit. The authors also reported increased spermatozoa mobility and increased testosterone levels and concluded that such a preparation can be used for infertility treatment.
Strength of evidence: Moderate for sperm concentration and motility based on pooled human data, though studies are heterogeneous and often not specifically standardized to the 5α-furostan-12-one-3β,22,26-triol component specifically.
Multiple clinical trials have evaluated whether furostanol-standardized extracts improve athletic performance. The available evidence is mixed. TT supplementation has been shown to enhance sports performance in many but not all studies. Data regarding the potential impact of TT supplementation on CrossFit® endurance is limited.
The world market offers pharmaceutical preparations and food supplements based on the saponin fraction of this plant; these are becoming popular among sports communities. More and more sportsmen prefer taking nutritional supplements with an androgenic effect instead of conventional steroids.
Strength of evidence: Weak. Available data do not consistently support significant improvements in body composition or performance outcomes beyond individual trial variability. The overall evidence base is insufficient for definitive conclusions.
According to published evidence, T. terrestris boosts testosterone secretion, regulates blood pressure, and protects the human body against injuries. The cardiovascular, reproductive, and urinary systems are all severely impacted. Steroidal saponins have an established cholesterol-related mechanism: protodioscin shows potential cardiovascular protection via increased expression of ATP-binding cassette transporter A1 (ABCA1) for reverse cholesterol transport.
Previous research has revealed steroidal saponins possess hypocholesterolemic effects, among other pharmacological activities. Some studies have proved that these extracts also have cardiovascular, cytotoxic, and antimicrobial activities.
Strength of evidence: Predominantly preclinical (in vitro and animal). Human clinical data specifically examining cardiovascular outcomes with furostanol-standardized preparations are limited.
Tribulus extract was shown to limit formation of calcium oxalate and calcium hydrogen phosphate dihydrate crystals, mineral compounds that can cause kidney stones. In an in vivo preclinical model, an acute oral toxicity study established the LD₅₀ to be greater than 2000 mg/kg body weight, and no observed adverse effect level (NOAEL) by repeated oral toxicity for 28 days at 750 mg/kg was noted.
The traditional use in Ayurveda as a diuretic and anti-urolithic agent has generated preclinical interest. Repeated use for 28 days did not produce harmful effects at the tested doses in rats. In addition, the extract reduced stone formation and helped maintain normal kidney structure and function. These findings suggest that Tribulus terrestris may be a potential candidate for supporting kidney health; however, further studies in humans are required before it can be recommended for clinical use.
Strength of evidence: Preliminary; largely animal and in vitro. Supportive of traditional use but without robust human clinical trial confirmation.
A large number of publications have revealed that steroidal saponins share different cytotoxic properties that promote their potential as anticancer drugs or adjuvants. Furostanol saponins from Tribulus terrestris fruits, including those with the 5α-furostan-12-one aglycone, have shown in vitro activity: two furostanol saponins from the dry fruits of Tribulus terrestris were isolated, and the inhibitory effects of the compounds on tumour cells were evaluated, with compounds showing potential anti-tumour activity.
Protodioscin from fenugreek (Trigonella foenum-graecum) induced cell death in the leukemic cell line HL-60 by apoptosis, while the gastric cancer cell line KATO III was merely inhibited with no apoptosis observed, demonstrating cell line-dependent activity.
Strength of evidence: Preclinical only. All anticancer data for this compound and its close structural relatives are from cell culture and animal studies. No human clinical evidence for anticancer benefit exists.
Because 5α-furostan-12-one-3β,22,26-triol is studied as a constituent of complex saponin extracts rather than as a purified molecule, all dosage data from clinical literature refer to the extract or preparation as a whole.
Commercial development aimed to produce a natural preparation with biologically active furostanolic saponins in sufficiently large concentration, such that a comfortable dose of 1–2 capsules per day could be made possible, working out to be 70–75% of the biologically active furostanolic saponins in the extracts.
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. Available toxicological data on Tribulus terrestris suggest a generally favorable safety profile at doses used in short-term studies.
Due to the saponin content of the plant, gastrointestinal disturbances may be seen in sensitive individuals. Transient GI problems including irritation of gastric mucosa and gastric reflux have been associated with consumption of Tribulus.
A 28-year-old man reported a severe case of nephrotoxicity after consuming Tribulus juice. Another case of reported toxicity involved a 30-year-old man who was diagnosed with acute tubular necrosis. A case report published in a peer-reviewed journal described: a case of T. terrestris-induced hepatotoxicity, nephrotoxicity, and neurotoxicity in an Iranian male patient who used the plant's extract to prevent kidney stone formation. He presented with seizure and very high serum aminotransferases and creatinine after consuming herbal water for 2 days. Discontinuation of the herbal remedy resulted in improvement in symptoms and normalization of his liver enzymes.
A further published case report noted: even after discontinuation of Tribulus for more than 2 months, severe liver and renal injury persisted, and only improved after plasmapheresis was performed. The case authors concluded: while Tribulus supplements are readily available claiming to help with sexual dysfunction, muscle building, and hypertension, these supplements present an increased risk of severe liver and renal dysfunction.
The steroidal saponin diosgenin is thought to be responsible for hepatotoxic effects associated with Tribulus.
Consumption of Tribulus causes motor neuron adverse effects in animals by affecting the gamma-aminobutyric acid (GABA) receptors. Excitation, menorrhagia, and insomnia were reported in a clinical study.
A reported rare side effect is gynaecomastia. Given the proposed androgenic mechanisms of furostanol saponins, use by individuals with hormone-sensitive conditions warrants attention.
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. Histology of the liver from sheep dying after feeding on this plant has shown crystals in bile ducts and renal tubules.
A critical consideration when evaluating all clinical data is that results of any single TT clinical trial should not be extrapolated directly to other TT preparations obtained from other regions, because saponin profiles—including the concentration of 5α-furostan-12-one-3β,22,26-triol—vary substantially based on geographic origin, plant part used, and extraction methodology. Various natural preparations based on extracts are available commercially but suffer from the limitation of variation in therapeutic efficacy or desirable results, with one major reason being the large variation in the content of the active compounds or the bioactive fractions.
Health conditions that 26-diol, 5 alpha-furostan-12-one-3 beta, 22, 26-triol may help support.
Body systems that 26-diol, 5 alpha-furostan-12-one-3 beta, 22, 26-triol may help support.
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