Antifungal activity of constituents from the heartwood of Gmelina arborea: Part 1. Sensitive antifungal assay against Basidiomycetes

Antifungal activity of constituents from the heartwood of the Malaysian Gmelina arborea against Trametes versicolor and Fomitopsis palustris was investigated. A sensitive bioassay system for antifungal activity against basidiomycetes was developed which uses a medium in which homogenized hyphae were dispersed. Ethyl acetate- solubles from the heartwood showed the highest activity against both fungi, although the activity against F. palustris was quite weak. Spots exhibiting antifungal activity against T. versicolor were specified by autobiography of ethyl acetate-solubles, and five constituents were isolated and identified as (+)-7′-O-ethyl arboreol, (+)-paulownin, (+)-gmelinol, (+)-epieudesmin and (−)-β-sitosterol. The four lignans showed antifungal activity, whereas β-sitosterol did not. From the comparison of antifungal activity, it was concluded that the piperonyl nucleus contributed to the activity of lignans. Of the four lignans isolated, gmelinol appeared to be an important antifungal constituent, since it was rich in the heartwood of G. arborea. Furthermore, the synergism by coexistence of these five compounds was confirmed.