Antifungal activity of essential oil isolated from Ocimum gratissimum L. (eugenol chemotype) against phytopathogenic fungi

An investigation of antifungal activity of the essential oil obtained by steam-distillation (1.1% w/w) of the aerial parts of Ocimum gratissimum and of an ethanolic extract from the steam-distillation residue was carried out using the agar diffusion method. The results revealed that the essential oil inhibited the growth of all fungi tested, including the phytopathogens, Botryosphaeria rhodina, Rhizoctonia sp. and two strains of Alternaria sp., while the extract from the residue was inactive. The essential oil was subjected to TLC bioautography used to detect fungitoxic constituents. The compound that showed antifungal activity was isolated and identified as eugenol. GC/MS analysis showed that eugenol was the main constituent of the essential oil studied. The antifungal activity of eugenol was evaluated against a species of Alternaria isolated from tomato (A1) and Penicillium chrysogenum. The minimal inhibitory concentrations of eugenol were 0.16 and 0.31 mg/disc for Alternaria sp. (A1) and P. chrysogenum, respectively