Horny Goat Weed (Epimedium) | Supplementopedia

Overview

Horny goat weed (Epimedium species, most commonly E. herba‑cimicifuga and E. sagittatum) is a perennial herb native to East Asia. It has been used in traditional Chinese medicine for over two millennia. Its primary use in modern nutraceuticals is to support sexual health, but contemporary research also points to broader physiologic activity, especially on endothelial function, bone metabolism, and neuro‑cognitive pathways.

Benefits

Sexual function: Randomized, double‑blind trials (e.g., 2008‑2021) report modest improvements in erectile rigidity and libido, largely attributed to the flavonoid icariin (≈30 % increase in penile blood flow in animal models).
Bone health: Pre‑clinical studies show icariin stimulates osteoblast differentiation and suppresses osteoclast activity, translating into modest BMD gains in post‑menopausal women (≈1–2 % over 12 months).
Cognitive support: In rodent models, icariin‑mediated inhibition of phosphodiesterase‑5 (PDE‑5) enhances cerebral blood flow and improves memory tasks; early human trials suggest modest benefits for short‑term memory in healthy adults.
Metabolic regulation: Icariin activates AMPK, improving insulin sensitivity and reducing fasting glucose by ~5 % in metabolic‑syndrome cohorts.
Bone‑joint and anti‑inflammatory: In vitro, icariin reduces NF‑κB activity, lowering pro‑inflammatory cytokines (IL‑6, TNF‑α) and alleviating osteoarthritis pain in pilot trials.

How It Works

Process: The principal bioactive, icariin (a prenylated flavonoid), exerts a multitarget profile.
PDE-5 Inhibition: It competitively inhibits phosphodiesterase‑5 (PDE‑5) and, to a lesser extent, PDE‑4, resulting in elevated cyclic‑GMP (cGMP) and cyclic‑AMP (cAMP) levels that promote vasodilation via nitric‑oxide (NO) pathways.
Estrogen Receptor Activation: Simultaneously, icariin activates the estrogen‑receptor‑β (ERβ) pathway, stimulating osteogenic gene expression (Runx2, OPG) while repressing RANKL‑mediated osteoclastogenesis.
CNS Effects: In the CNS, increased cGMP enhances synaptic plasticity and neuro‑vascular coupling.
AMPK Activation: Icariin also activates the AMPK‑SIRT1 axis, enhancing mitochondrial biogenesis and glucose uptake.
Antioxidant Activity: Its anti‑oxidant capacity derives from the catechol moiety, scavenging ROS and attenuating NF‑κB‑driven inflammation.

Dosage

Standardized Extracts: Typical standardized extracts contain 10–20 % icariin.
Clinical Studies: Clinical studies use 500–1 000 mg/day of a 30 % icariin extract (≈150–300 mg icariin) divided into two doses taken with meals to improve absorption.
Erectile Dysfunction: For erectile dysfunction, 500 mg twice daily is most common.
Bone Health: For bone health, 300 mg three times daily has shown bone‑marker efficacy.
Timing: 30 min before sexual activity or, for chronic metabolic support, with breakfast and dinner.
Special Cases:
- Athletes seeking fatigue reduction may use 200 mg once daily.
- Elderly women seeking bone support may use 600 mg divided 3×/day.
Titration: Always start at the low end (250 mg) to assess tolerance, then titrate up.

Safety & Side Effects

Common Side Effects: Common mild side effects: headache, dizziness, and gastrointestinal upset (2–5 % incidence).
High-Dose Effects: At doses >1 200 mg/day, reports of hypertension, tachycardia, and restless‑leg symptoms appear.
Contraindications: Contra‑indications: uncontrolled hypertension, severe cardiovascular disease, and hormone‑sensitive cancers (due to weak estrogenic activity).
Drug Interactions:
- Potentiates nitrates, phosphodiesterase inhibitors (e.g., sildenafil) → risk of hypotension.
- May augment anticoagulants (warfarin, clopidogrel) via platelet inhibition.
Avoidance: Pregnant or lactating women, children, and patients with severe liver disease should avoid use.
Monitoring: Monitoring of blood pressure and liver enzymes is recommended for >8 weeks of continuous therapy.

Chemistry

Icariin Structure: Icariin (C₃₃H₄₀O₁₅) is a flavonoid‑type prenylated flavonol glycoside: 5‑hydroxy‑7‑(2‑hydroxy‑3‑methoxy‑phenyl)‑8‑(2‑ribosyl)‑4‑methoxy‑flavone.
IUPAC: 7‑(2‑hydroxy‑3‑methoxy‑phenyl)-5,6‑dihydroxy‑8‑[2‑(4‑hydroxy‑2‑methoxy‑phenyl)‑2‑oxoethyl]‑2‑phenyl‑4‑H‑chromen‑4‑one (simplified representation).
Molecular Features: The molecule features a flavone core with a 3‑O‑rhamnosyl (glycosidic) moiety at C‑3, a prenyl chain at C‑8, and multiple phenolic hydroxyl groups conferring antioxidant activity.
Molecular Properties: Molecular weight: 676.66 g mol⁻¹; solubility: poorly water‑soluble (≈0.13 mg mL⁻¹), improved by ethanol or supercritical CO₂ extraction.

Sources & Quality

Harvest Locations: Commercial Epimedium is harvested primarily in Sichuan, Hunan, and Zhejiang provinces (China) and, to a lesser degree, in Japan and Korea.
Cultivation: Wild‑harvested plants are now largely supplanted by cultivated clones to ensure genetic consistency.
Extraction Methods: Extraction commonly uses 70 % ethanol or super‑critical CO₂, yielding a standardized 30 % icariin extract; some manufacturers employ aqueous‑ethanol to preserve flavonoid profile.
Quality Criteria:
- (i) ≥30 % icariin verified by HPLC‑UV.
- (ii) Absence of heavy metals (Pb, Cd < 0.5 ppm), pesticide residues, and microbial contamination (≤10³ CFU/g).
Recommendations: GMP‑certified facilities and third‑party testing (e.g., USP, NSF) are recommended for reliable supplementation.