Hops (Humulus lupulus)

Hops (Humulus lupulus) is a perennial climbing plant in the Cannabaceae family, cultivated primarily for its female inflorescences (“cones”). These cones contain a rich mixture of essential oils, bitter acids, and flavonoids. Historically used as a bittering, flavoring, and preservative agent in beer, modern research has identified several bioactive compounds that support human health, particularly through modulation of neurotransmission, inflammation, and hormonal pathways.

• α‑Acids:
  • Humulone, cohumulone, adhumulone (C({21})H() for humulone; molecular weight 354 g mol⁻¹).})O(_{5
  • IUPAC: (3R,6R,8S)-3,5‑dimethyl‑7‑(1‑hydroxy‑3‑methyl‑but-2‑enyl)‑2‑(3‑methyl­but‑2‑enyl)‑6‑propyl‑2,4‑dihydro‑3‑pyrone‑5‑carboxylic acid.
• β‑Acids: Lupulone (C({21})H() similar scaffold, more acidic).})O(_{5
• Prenylflavonoids:
  • Xanthohumol (C({21})H(), MW 354 g mol⁻¹) with a 6‑prenyl‑substituted chalcone structure; isoxanthohumol is the demethylated metabolite.})O(_{5
• Properties:
  • Lipophilic, soluble in ethanol, CO₂, and supercritical fluids.
  • Display moderate water solubility (≈ 0.1 g L⁻¹)
  • Stable at pH 3–5.
• Structure-activity relationship: The α‑acid lactone ring is critical for GABA(_A) modulation, while the prenyl side‑chain confers strong antioxidant activity.

• Cultivation: Commercial hops are cultivated in temperate regions.
• Major growers: United States (Pacific Northwest, especially Washington and Oregon), Germany, Czech Republic, and Slovenia.
• Processing: Harvested cones are dried, pelletized, or milled, then extracted using ethanol, CO₂, or super‑critical CO₂ to preserve volatile oils and bitter acids.
• Standardized extracts: Produced by solvent‑recovery processes that remove residual solvents to < 10 ppm per USP.
• Quality control:
  • HPLC quantification of humulone and xanthohumol.
  • Verification of microbial limits (≤ 1 × 10⁴ CFU g⁻¹).
  • Absence of pesticide residues (per EU/US limits).
• Recommendations: For research‑grade material, USDA‑certified organic hops and GMP‑certified manufacturers are recommended to ensure consistency and minimal contaminants.