Acronychia pedunculata (family: Rutaceae) is one of the commonly used medicinal plants in Sri Lankan traditional medicine. Different parts of this plant are used for the treatment of inflammatory conditions in the form of medicinal oils and herbal porridge.The present study aimed to evaluate the anti-nociceptive activity and anti-inflammatory activity with their mechanisms and the acute toxicity of crude extracts of the fresh leaves of A. pedunculata for scientific validation of the ethnopharmacological claims for this plant. Further, attention has been focused on the isolation of active compounds from active fractions of the crude extracts.The acute anti-inflammatory effect of the aqueous (AELA) and 70% ethanol crude extracts (EELA) and alkaloid fraction of A. pedunculata leaves were evaluated by the determination of inhibition of hind paw oedema induced by carrageenan in Wistar rats. Evolitrine was identified as the major alkaloid with significant bioactivities by column chromatography and NMR. The anti-nociceptive and anti-histamine activities of EELA and evolitrine were evaluated by acetic acid induced writhing and wheal formation tests respectively. In addition, in-vitro (2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay) and in-vivo (lipid peroxidation assay) anti-oxidant activity, nitric oxide (NO) inhibitory activity and acute toxicity of EELA were evaluated.Acute anti-inflammatory activity of AELA and EELA were dose-dependent. EELA was more active than AELA. The 200 mg/kg body weight (b. w.) dose of EELA was found as the minimum effective dose with maximum inhibition (78%) of oedema at 5th hour compared to the negative control (p < 0.05). Evolitrine was isolated and identified as an active anti-inflammatory and analgesic compound from active alkaloid fraction of EELA. Evolitrine showed activity enhancement when compared with crude EELA. The anti-inflammatory and analgesic activities of evolitrine (50 mg/kg b. w.) were comparable to that of reference drugs indomethacin (5 mg/kg b. w) and acetylsalicylic acid (100 mg/kg b. w.). The significant (p < 0.05) anti-histamine activity, DPPH scavenging in-vitro anti-oxidant activity, in-vivo lipid peroxidation inhibitory activity in-vivo, NO inhibitory activity of EELA as compared with relevant negative controls, were identified as probable mechanisms which mediated its anti-inflammatory action. Further, EELA showed a high safety margin in the limited dose acute toxicity study.The findings of the current study rationalize the usage of leaves of A. pedunculata in Sri Lankan traditional medicine as an analgesic and anti-inflammatory agent. Possible mechanisms mediating this activity included anti-histamine, anti-oxidant and NO inhibitory activities. Evolitrine is the major analgesic and anti-inflammatory compound isolated from the active alkaloid fraction of EELA.
