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 µ.g/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.

CONCLUSIONS

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.