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Hop cones preparations possess a wide range of biological activities including antimicrobial properties. In this work, we evaluated the effect of various organic extracts obtained from spent hops, as well as six hops flavonoids and their twenty natural and synthetic derivatives on human and plant microbial pathogens. Methylene chloride, acetone, ethyl acetate, and methanol were used as extractants. Seven flavonoids, among them two natural (α,β-dihydroxanthohumol and 8-prenylnaringenin) showed significant activity against methicillin sensitive and resistant Staphylococcus aureus and Staphylococcus epidermidis strains with the lowest MIC80 value of 0.5 µg/mL. The crude ethyl acetate, acetone, and methanol extracts from the spent hops exhibited antifungal activity against Fusarium oxysporum , F. culmorum, and F. semitectum with the lowest MIC50 of 0.5 mg/mL, while the methylene chloride extract exerted antifungal activity against Botrytis cinerea with the MIC50 of 1 mg/mL. The preparation obtained after the removal of xanthohumol from the spent hops crude extracts retained up to 95% of activity. These findings suggest that various spent hops extracts may be effective agents for the control of plant pathogens of economic importance, like Botrytis cinerea and Fusarium oxysporum , while some compounds from spent hops or their derivatives may become useful for staphylococcal infections.

Xanthohumol, a prenylated flavonoid from hops, and a supercritical carbon dioxide extract of spent hops were studied for their antifeedant activity against stored product insect pests: Sitophilus granarius L., Tribolium confusum Duv. and Trogoderma granarium Everts. Xanthohumol exhibited medium deterrent activity against the adults of S. granarius L. and larvae of T. confusum Duv. The spent hops extract was more active than xanthohumol towards the adults of T. confusum Duv. The potential application of the crude spent hops extract as a feeding deterrent against the stored product pests is proposed.

Hop tannin extract (HTE), produced by ethanol extraction of hops, is a material with brewing potential. Fresh and oxidised hop tannin extracts (OHTE) made from spent hop material were tested for their ability to reduce lautering time. The filtration of wort supplemented with HTE took ~20% less time than the control wort. The active dose of HTE was between 0.5 and 1.25 mL/L of brewing water (10–25 mg of gallic acid equivalents/L). HTE accelerated filtration more than the previously used gallotannins. The efficiency of HTE was influenced by oxidation. The filtration rate of worts adjusted with OHTE increased by <15% relative to the control wort. A pilot scale experiment showed the suitability of HTE application at the beginning of mashing and the analysis of sweet worts showed that the use of HTE slightly increased foam stability, but had no effect on wort colour. The mechanism of lautering acceleration was partly revealed by filtration of Congress worts adjusted with antioxidants and haze forming polyphenols. The antioxidant properties of polyphenolic extracts played only a minor role in this effect, which is likely to be influenced by a combination of factors originating from the polyphenol composition of HTE. © 2018 The Institute of Brewing & Distilling [ABSTRACT FROM AUTHOR]