Peppermint Oil (Mentha x piperita)

Peppermint oil (Mentha x piperita) is a volatile essential oil, not a significant source of macronutrients (negligible protein, fat, carbohydrates, and fiber at typical therapeutic doses of 0.1–0.4 mL). Its value lies entirely in its bioactive volatile compounds. Primary bioactive compounds: Menthol (30–55% of oil composition) is the dominant monoterpenoid responsible for most pharmacological effects; menthone (14–32%) contributes to antimicrobial and analgesic properties; 1,8-cineole (eucalyptol, 3–14%) provides anti-inflammatory and bronchodilatory activity; menthyl acetate (2–10%) adds spasmolytic effects; menthofuran (1–9%) contributes to hepatic metabolism interactions; limonene (1–5%) offers antioxidant and anti-inflammatory properties; pulegone (typically <4% in quality oils, higher levels are hepatotoxic) is a minor monoterpene ketone. Additional bioactive constituents: Rosmarinic acid (a polyphenolic ester, trace amounts in the oil but significant in peppermint leaf extracts at ~1.5–4% dry weight) provides potent antioxidant and anti-allergenic activity; luteolin and eriocitrin (flavonoids found primarily in aqueous/ethanolic extracts rather than the essential oil). Micronutrients: The essential oil itself contains negligible vitamins and minerals; however, peppermint leaf (the source material) provides manganese (~1.1 mg per 2 g dried leaf), iron (~0.5 mg per 2 g), calcium, and small amounts of folate and vitamin A (as carotenoids). Bioavailability notes: Menthol is rapidly absorbed through oral, dermal, and inhalation routes with high bioavailability (~35–55% oral bioavailability after first-pass hepatic metabolism via glucuronidation and CYP-mediated oxidation). Enteric-coated capsules (e.g., 0.2 mL peppermint oil per capsule) bypass gastric degradation, improving intestinal delivery for IBS treatment by approximately 3–4 fold compared to non-coated forms. Transdermal absorption of menthol is enhanced by its own penetration-enhancing properties, reaching peak plasma levels within 1–2 hours. Menthol's half-life is approximately 3–6 hours, with excretion primarily via urine as menthol glucuronide.