Indian Journal of Agricultural Biochemistry

Crude and different solvent (EtOAc, n-BuOH and MeOH) fractions of Cassia fistula Linn. were evaluated for their effectiveness for inhibition of conidial germination of Alternaria brassicae. MeOH fraction was most effective with a minimum inhibitory concentration of 290μg/ml. The subsequent bioassay guided fractionation and isolation of bioactive compounds of methanolic leaf extract of Cassia fistula was done on open column liquid chromatography. CSFs II and IV were effective at 2.5% dilution (16.5 and 14.75 μg/ml), whereas CSFs III, V, VI, VII and VIII were effective at 5% dilution (29.75–33 μg/ml). Methanolic crude extract and CSF I of Cassia fistula exhibited antifungal activity against A. brassicae by direct bioautography. The effect of CSFs of Cassia fistula was observed on development of Alternaria blight using detached-leaf inoculation method. Only CSF I at concentration of 80μg/ml (10% dilution) completely inhibited lesion development of A. brassicae on detached leaves of Indian mustard. TLC bioautography with A. brassicae and diagnosis with Godin reagent indicated the presence of bioactive saponins in CSF I of Cassia fistula.