Evaluation of analgesic activity of ethanolic and aqueous extracts of leaf of Plumeria rubra in albino rat

Objective : Plumeria rubra is an important traditional medicinal plant used in various ailments and the indigenous plant as a medicament for treatment of various inflammatory conditions is well documented in literature. The analgesic activity was evaluated by hot-plate and acetic acid induced writhing methods. Methods : The leaves of P. rubra were collected from the local area in and around Palakkad, Kerala (India). About 1500 g of the powder was extracted using Soxhlet apparatus for 12 h using 5.0 L of Ethanol as solvent. The test extracts was administered intraperitoneally at a dose of 100 and 200 mg/kg while Pentazocine (5 mg/kg) and diclofenac sodium (10 mg/kg) served as standards. Results : The ethanolic extract of 200 mg/kg having significant analgesic activity in Acetic acid induced abdominal writhing response and percentage of inhibition (PI) (p<0.01 )when compared to control.. The Ethanolic extract of 100 mg/kg and 200 mg/kg exhibited significant analgesic activity in the hot plate method (p<0.001) by increasing the pain reaction time (PAT) of the rats to  sec 7.25±0.38 at 45 min after treatment in comparison to control (4.08±13). Conclusions : The results suggest that ethanolic extracts of P. rubra possesses potent analgesic properties, which support its use in traditional medicine and suggesting that the plant should be further investigated for its pharmacological active natural products.