Antiradical and antioxidant activity in vitro of hops-derived extracts rich in bitter acids and xanthohumol

• Published in: Industrial crops and products 2021-03, Vol.161, p.113208, Article 113208
• Main Authors: Kontek, Bogdan, Jedrejek, Dariusz, Oleszek, Wiesław, Olas, Beata
• Format: Article
• Language: English
• Subjects: Antiradical test; Bitter acids; Hops; Oxidative stress; Plasma; Prenylchalcones
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2020.113208

[Display omitted] •Lupulin-associated metabolites were easily separated from hops methanolic extract.•α- + β-acids extract had similar composition to hop bitter acid reference mixture.•α- + β-acids were better radical scavengers than α-acids + xanthohumol.•Lupulin metabolites attenuated oxidative stress in a plasma test system in vitro.•Bitter acids showed the best activity in lipid peroxidation and protein carbonylation tests. Humulus lupulus L. is known to have preservative, mild sedative, hypnotic, and estrogenic properties that are related to its chemical composition. Hops are widely used in brewing, also in pharmacy, and cosmetics. Moreover, the continuous development of biological research creates new application possibilities. The present paper was to measure the previously demonstrated antiradical and antioxidant properties of hop bitter acids and prenylflavonoids using a human plasma test system. Firstly, lupulin-associated metabolites were collected into two A–B fractions which were phytochemically characterized using UPLC–PDA–MS/MS analyses. Fraction A was a mixture of α- and β-acids (623 mg/g of dry weight (DW)) and fraction B was enriched in α-acids (275 mg/g DW) and xanthohumol (102 mg/g DW). Hop bitter acid preparation (A) was a better scavenger of 2,2′-azinobis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals compared with extract B, however, both extracts presented rather a moderate antiradical activity (25–30 % of Trolox power). For comparison, a commercial mixture of bitter acids showed a similar effect to extract A, while xanthohumol had little activity. Both A–B preparations demonstrated antioxidant capacity in established plasma test system in vitro as the protective effect on plasma macromolecules against oxidative stress induced by H2O2/Fe was observed. A mixture of bitter acids (extract A) was found to be highly active, more than extract B, in lipid peroxidation and protein carbonylation tests – alleviated oxidative stress by 65–95 %. The obtained results broaden the current state of knowledge about the multifunctional activities of hops-associated metabolites and demonstrate that bitter acids make an important contribution, no less than prenylflavonoids, to the antioxidant capacity of hop cones extract.