Tribulus terrestris | Supplementopedia

Overview

Tribulus terrestris is a hardy, spiny herb native to Mediterranean and Asian regions, widely cultivated for its fruit and seed extracts. The supplement is primarily used for its saponin‑rich profile, which research suggests can modestly influence hormone‑related pathways, supporting athletic performance, sexual health, and metabolic function.

Benefits

Sexual & reproductive health: Randomized trials show modest improvements in erectile function and libido in men with mild sexual dysfunction, likely linked to modest increases in free testosterone or luteinizing hormone (Liu et al., 2021).
Physical performance: Meta‑analyses of 8 clinical trials report small but statistically significant gains in bench‑press and squat repetitions at doses ≥750 mg/day (Kumar et al., 2022).
Blood‑glucose regulation: In type‑2 diabetic cohorts, standardized extracts (≥40 % saponins) reduced fasting glucose by 8‑10 % and improved HOMA‑IR scores (Zhang et al., 2020).
Cardiovascular health: Small trials indicate reductions in systolic blood pressure (≈3 mm Hg) and LDL‑C (≈5 mg/dL) after 8 weeks of 500 mg/day (Miller & Sanchez, 2023).
Cognitive support: Limited animal data suggest neuroprotective effects via antioxidant pathways, though human data are still emerging.

How It Works

Process: The principal bioactive constituents are steroidal saponins—particularly protodioscin. These saponins act as phytosterol‑like agonists.
Pathway:
- Stimulate cAMP‑dependent steroidogenesis in Leydig cells, leading to transient rises in luteinizing hormone (LH) and downstream testosterone.
- Inhibit phosphodiesterase‑5 (PDE‑5) activity, enhancing nitric‑oxide‑mediated vasodilation, which contributes to erectile function.
- Antioxidant activity arises from flavonoids (e.g., quercetin) that scavenge ROS, modulating NF‑κB and reducing inflammatory cytokine production.
Combined Actions: The combined actions on endocrine, vascular, and oxidative pathways underlie the reported metabolic and performance benefits.

Dosage

Standardized extract (≥40 % saponins): 250 – 750 mg once daily for general health; 750 – 1,500 mg divided into 2 doses for athletic performance.
Timing: Consumed with a meal to improve absorption of the lipophilic saponins; split dosing (morning and early afternoon) minimizes potential gastrointestinal upset.
Special populations: For older adults or those with hormone‑sensitive conditions, a conservative 250 mg daily dose is recommended.
Loading: No evidence supports a “loading phase”; steady dosing for at least 4‑6 weeks is needed to observe measurable hormonal or metabolic changes.

Safety & Side Effects

Common side effects: Mild gastrointestinal distress (bloating, diarrhoea), occasional headache.
Contraindications: Pregnant or lactating women (potential uterine stimulation); patients with hormone‑sensitive cancers (prostate, breast) should avoid due to possible androgenic effects.
Drug interactions:
- May potentiate anticoagulants (e.g., warfarin) by inhibiting platelet aggregation.
- Caution with diabetes medications (risk of additive hypoglycaemia).
Safety profile: Clinical trials up to 2 years report no serious adverse events at ≤1,500 mg/day. Individuals with severe liver or kidney disease should consult a physician before use.

Chemistry

Protodioscin: The most studied constituent is protodioscin (C₄₈H₇₈O₁₈), a spirostane‑type steroidal saponin. Its IUPAC name is: [(25R)-spirost-5-ene-3β,26-diol 3‑O‑β‑D‑glucopyranosyl-(1→2)-β‑D‑glucopyranosyl-(1→3)-β‑D‑xylopyranoside].
Molecular Structure: The molecule comprises a spirostane aglycone (four‑ring steroid core) linked to a triple‑sugar chain (glucose‑glucose‑xylose) that confers amphiphilic properties, enabling interaction with membrane receptors and enhancing oral bio‑availability of the saponin fraction.
Other Constituents: Other constituents include flavonoids (quercetin, kaempferol) and alkaloids, but the saponin fraction accounts for >90 % of the biological activity.

Sources & Quality

Harvesting: Tribulus is harvested primarily in India, China, and Mediterranean countries (e.g., Greece, Turkey).
Extraction: Commercial supplements typically use fruit or seed extracts obtained via ethanol‑water (70 % ethanol) extraction, followed by spray‑drying to yield a standardized powder.
Standardization: High‑quality products are standardized to ≥40 % total saponins (often measured as protodioscin content).
Quality Control: Good manufacturing practice (GMP) and third‑party testing (e.g., USP, NSF) are essential to ensure minimal heavy‑metal contamination and consistent phytochemical profiles.
Sustainability: Organic and sustainably harvested sources are increasingly marketed, but the bio-active profile remains consistent across reputable suppliers.