Pharmacological Evaluation of Antiasthmatic Activity of Myrica nagi Bark Extracts

Background: The involvement of debilitating side effects of allopathic antiasthmatic drugs provides a strong impetus for the development of new herbal therapeutics. Myrica nagi Thunb. (Syn. Kaiphal) of Myricaceae family is a known drug of the Ayurveda system used for the treatment of several diseases including asthma. Methods: The present study deals with the preparation and phytochemical screening of polar, non-polar and methanolic extracts of Myrica nagi bark followed by the evaluation of their antiasthmatic activity using four different animal experimental models: acetylcholine induced bronchospasm in conscious guinea pigs, acetylcholine induced contraction on isolated guinea pig tracheal chain preparation, compound 48/80 induced mast cell degranulation using rat, and trypsin and egg albumin induced bronchospasm in conscious rat. Results: Polar extract of M. nagi bark (200 mg/kg, p.o.) exerted strong antiasthmatic effects near to Ketotifen (1 mg/kg, p.o) as standard drug. Polar extract of M. nagi bark (200 μg/ml) significantly inhibited Ach induced contraction of isolated guinea pig tracheal chain preparation. Pre-incubation of rat peritoneal mast cells with test drugs (methanolic, non polar and polar extracts) showed dose dependent significant reduction of % mast cell degranulation. Polar extract (200mg/kg) & Methanolic extract (200mg/kg) of M. nagi bark treated animals showed significantly lesser serum bicarbonate level, higher tidal volume, lower level of eosinophils and neutrophils. Conclusion: The results of present investigation suggest that the polar extracts of Myrica nagi bark have better antiasthmatic activity than the non polar and methanolic extract.