Anti-inflammatory and analgesic activities of the methanol leaf extract of Phyllanthus amarus in some laboratory animals.

Background: Phyllanthus amarus is used in Nigeria and other parts of the world as a medicinal plant. The plant has a history of use in Ayurvedic medicine for over 2000 years as well as a wide variety of traditional applications. It is being evaluated for anti-inflammatory and analgesic potential because these phenomena have assumed a worldwide dimension as a result of their implications in a variety of diseases.

Methods: The methanol extract of the leaves of P. amarus was investigated for its anti-inflammatory and analgesic activities in Wistar strain albino rats and mice using carrageenan-induced inflammation as well as histamine-induced edema. The analgesic effect was determined using acetic acid writhing method and formalin-induced paw lick test. Standard phytochemical analysis was carried out to determine the active constituents responsible for biological effects.

Results: The extract at 100 and 200 mg/kg reduced significantly (p<0.05) the formation of edema induced by histamine and carrageenan. In the acetic acid-induced writhing test, the extract showed good analgesic activity characterized by a significant reduction in the number of writhes with 100 and 200 mg/kg doses used when compared to the control group. In the formalin-induced paw lick test, the extract at 100 and 200 mg/kg doses exhibited good analgesic activity characterized by a significant reduction in the number of paw licks at both the early and the late phases of the induced pain when compared with the untreated control group. Ibuprofen at 10 mg/kg served as the reference drug in all these tests.

Conclusions: Results suggested that methanol extract of the leaves of P. amarus has great anti-inflammatory and analgesic potential. These biological effects exhibited by the extract of this plant may be attributed to the presence of flavonoids and other phenols contained therein.