In vitro antifungal activity of Thai herb and spice extracts against food spoilage fungi

Screening of Thai herbs and spices was carried out to investigate their in vitro antifungal activity against Aspergillus niger, A. oryzae and Penicillium sp. by using agar well diffusion method. Of thirteen plants tested, crude ethanol extracts of three, namely Piper betel, Boesenbergia pandurata, Andrographis paniculata exhibited antifungal activity against all test microorganisms. Penicillium sp. was more resistant to the extracts than A. niger and A. oryzae. The antifungal index of the selected plant extracts with various concentrations against test fungi was measured by agar dilution assay. With the increase of the concentration, the antifungal activity also increased. A complete fungal inhibition was observed when Piper betel extract concentration exceeded 1.50 percent (v/v). The antifungal index from the other plants ranged from 30 to 60 percent.