Chemical variability and antifungal activity of phenolic lipids from several Gramineae

Abstract

An important class of phenolic lipids is alkylresorcinol (AR)-related compounds, which have been identified in many plants, fungi taxa, bacteria and some animals. Furthermore, there are several studies indicating that AR exhibit potent antimicrobial activity in plant defense possibly by their amphiphilic nature. This type of compounds can be found in large proportions in cereal grains such as wheat, rye, triticale and barley, whose occurrence is mainly located within the outer cuticle of the seed. As part of our research on antifungal compounds, the chemical profile and antifungal activity of extracts obtained from a set of 21 grasses were investigated. The chemical profile was determined by measuring total AR content (TAC) using Fast Blue RR protocol and by LC-DAD and LC-MS analysis of the resulting extracts for comparative drives by chemometrics through principal component analysis (PCA). TAC values indicated that triticale bran and wheat bran had the highest AR amounts with 45.0 and 33.1 mg AR/g dried material, respectively. In addition, the acetone-soluble extracts were evaluated in vitro against Fusarium oxysporum. The highest inhibition percentage against F. oxysporum was found for triticale bran-derived extract (81.9 and 76.9% at 10.0 and 1.0 µg/mL, respectively). The LC-DAD and LC-MS profiling for the 21 extracts led us to identify the some AR, involving AR with alkyl and alkenyl side chains possessing 13 – 19 carbons (tetradecenyl and hydroxytetradecenylresorcinol as main AR). Multivariate analysis (PCA) was performed on chromatographic data for all extracts. PCA-derived score plot showed that there is a relationship between the content of ARs and the antifungal activity. A bioguided fractionation leading to the isolation of the active AR is currently in the course.