Antifungal Activity of Hop Leaf Extracts and Xanthohumol on Two Strains of Venturia inaequalis with Different Sensitivities to Triazoles

Abstract

Hop cones are well-known for their antimicrobial properties, attributed to their specialized metabolites. Thus, this study aimed to determine the in vitro antifungal activity of different hop parts, including by-products such as leaves and stems, and some metabolites against Venturia inaequalis, the causal agent of apple scab. For each plant part, two types of extracts, a crude hydro-ethanolic extract and a dichloromethane sub-extract, were tested on spore germination of two strains with different sensitivities to triazole fungicides. Both extracts of cones, leaves and stems were able to inhibit the two strains, whereas rhizomes did not show activity. The apolar sub-extract of leaves appeared as the most active modality tested with half maximal inhibitory concentrations (IC50) of 5 and 10.5 mg·L−1 on the sensitive strain and the strain with reduced sensitivity, respectively. Differences in activity level between strains were noticed for all active modalities tested. Sub-extracts of leaves were then separated into seven fractions by preparative HPLC and tested on V. inaequalis. One fraction, containing xanthohumol, was especially active on both strains. This prenylated chalcone was then purified by preparative HPLC and showed significant activity against both strains, with IC50 of 1.6 and 5.1 mg·L−1. Therefore, xanthohumol seems to be a promising compound to control V. inaequalis.

Exploring Plant Extracts as a Novel Frontier in Antimicrobial Innovation: Plant Extracts and Antimicrobials

“…In a separate study, Moreau et al [ 3 ] investigated the antifungal properties of various components of hops ( Humulus lupulus L.) against Venturia inaequalis (Cooke) G. Winter, the causative agent of apple scab. Extracts from hops, including leaves and stems, and some of their specific metabolites, were tested in vitro.…”