Direct bioautography for the screening of selected tropical wood extracts against basidiomycetes

Abstract

Abstract To understand the reasons for the high durability of tropical wood species, the chemistry of the extractives needs to be elucidated. As these extractives consist of a great variety of components differing in quantity and composition, the analysis is often time-consuming. To focus on the key bioactive substances, bioassay-guided fractionation is helpful, but the established bioassay methods cannot be readily adapted to basidiomycete fungi that are commonly used for the respective durability tests, because they do not sporulate easily in laboratory settings. The research therefore aims at developing a direct bioautography using homogenized hyphae from basidiomycetes, to overcome this restriction. Extracts from four tropical wood species were analyzed regarding their potential bioactivity on two selected basidiomycete fungi. To this end, the chemically complex mixtures and extract constituents were resolved by a two-dimensional planar chromatography and the metabolites were located by characteristic zones of fungal growth inhibition, which was accentuated by a color reaction. The bioactive fractions were analyzed by gas chromatography/mass spectrometry (GC/MS). Potentially responsible compounds could be identified, such as the alkaloid bicuculline from Mezilaurus itauba, which has not been described in this species yet. The presented bioassay method can be used as a rapid screening method for bioactive components from wood.