Water Extract of Leaves and Stems of Preflowering but not Flowering Plants of Anisomeles indica Possesses Analgesic and Antihyperalgesic Activities in Rats

摘要

According to Sri Lankan traditional medicine, a decoction made from stems and leaves of Anisomeles indica Kuntze (Lamiaceae) possesses analgesic activity. However, the validity of this claim has not been scientifically tested. The aim of this study was to investigate analgesic and antihyperal-gesic activities of this plant using a water extract made from the leaves and stems. The water extracts were made from leaves and stems of both preflowering (El) and flowering plants (E2). El showed a dose-dependent analgesic effect up to 6h of treatment when tested in rats using the hot plate and the tail flick techniques. Further, the analgesic effect of El was not accompanied by toxic effects. This effect was neither gender dependent nor dependent on the stage of the estrous cycle. El also showed a dose-dependent antihyperalgesic activity in the hot plate test. In contrast, E2 did not show any analgesic effect (500mg/kg). The analgesic effect produced by El was not abolished by naloxone. El dose-dependently retarded the amplitude of the spontaneous contractions of isolated dioestrous rat uterus. Further, El induced a dose-dependent plasma membrane stabilisation effect on rat ery-throcytes. Collectively, these observations suggest that the analgesic and antihyperalgesic effects of El are mediated from inhibition of COX-1, thus impairing the synthesis of prostaglandins. A change in chemical contents that accompanies flowering could be one possible reason for the inability of E2 to demonstrate analgesic effect.