Isolation and characterization of mosquito larvicidal compounds from leaves of Kotschya uguenensis (Taub) F. Whote

Abstract

At 72h of exposure, the crude extract showed larvicidal activity with LC50 values of 94.01 µg/mL against An. gambiae. Based on bioactivity-guided fractionation, a new ent-halimane type diterpene, named ent-halim-1(10)-ene-15-oic acid (1) together with a known 3-O-methyl-D-chiro-inositol (3) were isolated and identified as the active constituents. Ent-halim-1(10)-ene-15-oic acid (1) and 3-O-methyl-D-chiro-inositol (3) exhibited strong larvicidal activity with LC50 value of 30.05 and 80.73 µg/mL µg/mL, respectively (>95% CI) after 72 h post exposure. The extract and the two compounds (1 and 3) had no significant activity at 24 and 48 h. However the ent-halim-1(10)-ene-15-oic acid (1) demonstrated strong activity against An. gambiae with significant different being observed against the extract and compound 3. The results indicated that 80% aqueous ethanol leaves extract of K. uguenensis and the two isolated constituents have potential for development in the control of An. gambiae larvae.