Antifungal activity of Acacia nilotica extracts in control of Colletotrichum gloeosporioides [Penz.] fungi causing anthracnose of mango fruits

Antifungal activity of Acacia nilotica and a number of other plants extracts was evaluated to control anthracnose disease of mango fruits. During the study leaf extracts of seven plants viz., Acacia nilotica (ethyl alcohol), Citrus aurantifolia (ethyl acetate), Murraya koenigii (ethyl acetate), Nerium indicum (ethyl acetate), Ocimum gratissimum (petroleum ether, benzene, ethyl acetate, ethyl alcohol,), Ocimum sanctum (petroleum ether), Prunus persica (ethyl acetate) and bark extract of Acacia farnesiana (ethyl acetate) and Acacia nilotica (benzene, ethyl acetate, ethyl alcohol, methanol) showed 100 per cent activity against Colletotrichum gleoesporioides. The bark of A. nilotica showed 100 % activity in four organic solvents viz. benzene, ethyl acetate, methanol, ethyl alcohol. Therefore the bark of A. nilotica was selected for further investigations. The maximum inhibitory dilution of ethyl acetate, benzene, methanol and ethyl alcohol extracts of A. nilotica were determined to be 1:10,1:2,1:8,1:9 respectively. All the extracts of A. nilotica showed broad antifungal activity against ten fruit rotting fungi. The extracts showed significant inhibition in conidia germination of C. gloeosporioides. The effect of storage and temperature on fungitoxicity of A. nilotica extracts was also evaluated. Antifungal activity of some of the compounds isolated from the bark of A. nilotica was also tested. Kaempferol and Kaempferol 3-O-rhamnoside were found to be active against the test fungus and the structure activity relationship amongst kaempferol and kaempferol-3O-rhamnoside was also determined. An in vivo trial with the aqueous extract of A. nilotica bark showed enhancement of shelf life of mango fruits by preventing them from fungal rotting.