RESUMO
Various parts of Annona squamosa Linn. (custard apple) have long been used in Thai folk medicine. The effectiveness of organic solvent extracts of custard apple seeds and leaves against headlice has been reported. The present study is focused on the efficacy and stability of seed extract prepared as a cream. A petroleum ether extract of seeds was prepared as a 20% w/w oil in water cream and tested for anti-headlice activity in school girls. After a 3 hour-hair exposure to 20 g of freshly prepared custard apple cream, 95.34+/-1.96% of headlice were killed. This killing rate was higher than that obtaned from the control (cream base) or the standard drug (25% benzyl benzoate emulsion). The anti-headlice efficacy of the 6 and 12 month-storage preparations kept in a refrigerator and 12 month-storage at room temperature were 99.19+/-0.60%, 97.55+/-2.06% and 89.47+/-3.64%, respectively, which were not significantly different from that of the freshly prepared cream. This cream did not cause any irritant effect on the scalp or neck skin while benzyl benzoate emulsion produced burning sensation or redness. The results demonstrate that the petroleum ether extract of Annona squamosa seeds prepared as a cream is stable for at least 12 months. The custard apple cream may be, therefore, suitable for use as an alternative therapy against headlice.