Anti-phytopathogenic fungal activity from some Thai medicinal herb extracts

Abstract

Screening of antifungal activity from eighteen plant extracts were evaluated on six phytopathogenic fungi; Alternaria brassicicola, Colletotrichum gloeosporioides, Fusarium oxysporum, Phytophthora palmivora, Pythium sp. and Sclerotium sp. Cultures of phytopathogenic fungi on PDA were incorporated with plant powder at concentration 50,000 ppm. Acorus calamus exhibited antifungal activity to all six phytopathogenic fungi higher up to 61%, especially for P. palmivora. The percentage of mycelial growth inhibition varied with species of plant materials. Moreover, different parts of plant materials revealed different levels on mycelial growth inhibition. Furthermore, some plant species showed the selectivity to inhibit certain fungi. Investigation of antifungal acitivity of dichloromethane and methanol crude extracts at concentration 10,000 ppm found that only dichloromethane extract displayed 100% mycelial growth inhibition to all six phytopathogenic fungiwhile the methanol crude extract had no activity. For evaluation of dichloromethane crude extract on mycelial growth inhibition at various concentrations, Pythium sp was inhibited at the lowest concentration of IC[subscript 50] 22 ppm. Chemical constituents of the dichloromethane extract of A. calamus gave 3 antifungal compounds characterized as beta-asarone, alpha-asarone and 2,4,5-trimethoxybenzaldehyde which confirmed their antifungal activity by bioautographic technique with A. brassicicola, C. gloeosporioides and F. oxysporum