Influence of Extraction Methods on Polyphenol Profile and Antiradical Activity of Hops

TL;DR

This study compares how different extraction methods affect the polyphenol content and antioxidant activity of hops, finding that aqueous acetone is more effective for isolating bioactive compounds.

Contribution

The study introduces a comparative analysis of extraction methods for hop polyphenols and their impact on antioxidant activity.

Findings

Aqueous acetone extraction yields higher anthocyanogens and prenylflavonoids with greater antiradical activity.

Hot-water extraction results in higher total polyphenols but lower antioxidant capacity.

Antiradical activity in acetone extracts is influenced by bitter acids in addition to polyphenols.

Abstract

Hop polyphenols contribute to beer stability and possess a wide range of biological activities; however, information on how extraction conditions influence their recovery and antioxidant potential remains limited. This study aimed to compare hot-water extraction, simulating wort boiling, with 80% aqueous acetone extraction as initial sample preparation steps for assessing the polyphenol content and antiradical activity of hops. Sample sets of four Czech hop cultivars from two contrasting harvest years were examined. Group-type polyphenols, total polyphenols, anthocyanogens, flavanoids and UHPLC–HRMS flavonoid profiles were evaluated. Antiradical activity was evaluated by the DPPH assay. Extraction solvent markedly affected both the composition and antiradical properties of hop extracts. Aqueous acetone provided substantially higher yields of anthocyanogens and prenylflavonoids and consistently higher antiradical activity, particularly in cultivars with elevated α-acid content. In contrast, hot-water extracts yielded slightly higher total polyphenols but significantly lower anthocyanogens and reduced antioxidant capacity. Correlation analyses showed that antiradical activity in water extracts was strongly driven by polyphenol levels, whereas in acetone extracts it was influenced by additional constituents, including bitter acids. Extraction solvent critically determines the polyphenolic profile and antioxidant behavior of hop extracts. Aqueous acetone proved more effective for isolating bioactive polyphenol fractions relevant to antiradical performance.

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