In Vitro Antioxidant, Metal-Chelating, and Enzyme-Inhibitory Potential of Hop Leaves and Cones
DOI:
https://doi.org/10.20883/medical.e1718Keywords:
Humulus lupulus, xanthohumol, enzyme inhibition, sustainability, by-productAbstract
Aim. Hop leaves represent an underutilised by-product of hop cultivation and a potential source of bioactive compounds. This study aimed to compare the chemical composition, antioxidant activity, metal-chelating capacity, and enzyme inhibitory potential of leaves and cones from four hop cultivars (Blisk, Nugget, Bačka, and Saphir).
Material and methods. Hop leaf and cone extracts were chemically characterised, and their antioxidant, metal-chelating, and enzyme-inhibitory activities were evaluated using in vitro assays. Total phenolic content (TPC) was determined spectrophotometrically, while xanthohumol and lupulone were quantified by HPLC. Chemical profiles were characterised using GC–MS. Antioxidant activity was evaluated using DPPH, ABTS, FRAP, and CUPRAC assays. Metal-chelating activity and the inhibition of acetylcholinesterase, butyrylcholinesterase, and tyrosinase were also assessed.
Results. Cones exhibited higher TPC and greater concentrations of xanthohumol and lupulone than leaves. The highest TPC was recorded for Blisk cones (22.01 mg GAE/g), whereas leaves contained 6.54–12.70 mg GAE/g. Blisk cones contained the highest xanthohumol concentration (2.55 mg/g) and showed the strongest cholinesterase inhibition, with IC50 values of 15.9 mg/mL and 17.98 mg/mL against acetylcholinesterase and butyrylcholinesterase, respectively. Among the leaves, the Blisk cultivar exhibited the highest antioxidant activity and enzyme-inhibitory potential, with acetylcholinesterase inhibition (IC50 = 20.4 mg/mL) comparable to that of selected cone samples. In contrast, metal-chelating activity was stronger in leaves (IC50 = 3.17–3.64 mg/mL) than in cones (5.93–10.91 mg/mL). Principal component analysis indicated associations between phenolic content, antioxidant activity, and cholinesterase inhibition.
Conclusions. These findings demonstrate that hop leaves are a valuable source of compounds with antioxidant, metal-chelating, and enzyme-inhibitory activities that may be relevant to neuroprotection. In particular, leaves of the Blisk cultivar exhibited biological activity comparable to that of selected cone samples, supporting their further investigation for food, nutraceutical, and pharmaceutical applications.
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