Isolation and identification of allelochemicals from sugarcane leaves

Sequential partitioning of the aqueous extracts of sugarcane leaves against a series of solvents of increasing polarity separated the most active compounds in diethyl ether fractions. The other active fractions included ethyl acetate, petroleum ether and dichloromethane. The activity was determined by lentil root growth assay. Bioassays after TLC indicated two major zones of activity. Further separation of diethyl ether extract revealed two new toxic compounds viz., 2,4-dihydroxy-1, 4-benzoxazin-3-one (DIBOA) and benzoxazolin-2-one (BOA) in sugarcane leaves. In bioassay, DIBOA and BOA inhibited the root growth of lentil seedlings by 50% or more at 0.45 mM and 1.25-mM concentrations, respectively. Only DIBOA showed significant activity on wheat, but nether of the compounds inhibited the seed germination at concentrations tested.