Analysis of the fungicidal constituents from the bark of Ocotea usambarensis Engl. (Lauraceae)

Abstract

AbstractThe dichloromethane extract of the bark of Ocotea usambarensis Engl. (Lauraceae) showed antifungal activity against Cladosporium cucumerinum. This activity was shown to be linked with its essential oil content together with the presence of the lignan (+)‐piperitol. Gas chromatography‐mass spectrometric (GC‐MS) analysis of the oil allowed the identification of about seventy compounds. In order to determine the fungicidal active components of the oil, further separation was required. Instrumental preparative thin layer chromatography (TLC) was chosen because it was a very suitable method to be followed by direct bioautography.Analysis of the fractions by GC‐MS combined with instrumental bidimensional TLC and direct bioautography allowed the separation and identification of the four main active compounds. Nerolidol, α‐terpineol, α‐copaen‐ 11‐ol and a further unidentified sesquiterpene alcohol were shown to be fungicidal. Identification was made by comparison of the mass spectra with a computerised data‐bank and the literature, together with the comparison of retention indices on two GC columns with literature values and with some commercially available samples.