Chemical characterization and phytotoxicity of volatile essential oil from leaves of Anisomeles indica (Lamiaceae)

Abstract The present study investigated the phytotoxic effect of foliar volatiles of Anisomeles indica . Laboratory bioassay with the detached leaves of A. indica inhibited the radicle and seedling elongation and dry weight accumulation of four test weeds, viz., Bidens pilosa, Cassia occidentalis, Amaranthus viridis and Echinochloa crus-galli depicting a dose–response relationship. On further investigation, yellowish-brown pungent smelling oil was extracted from the leaves. GC–MS analyses of the oil revealed 26 constituents with equal proportions of mono- and sesquiterpenes. α -Bisabolol oxide B, a sesquiterpene oxide, was the major component (∼21%) followed by dihydro- β -ionone, hexyl butanoate, tetracosane, and vitispirane (all > 5%). The oil inhibited radicle growth, seedling elongation and dry matter of the test weeds in a dose–response manner. The study concludes that foliar volatiles of A. indica emitted in the air suppress other plants, and may have several ecological implications like plant–plant interactions and the possibility of utilization for weed control.