Water relationships in Phyllantus orbicularis and Punica granatum antiviral extracts and their influence on stability after freezing and freeze-drying

The effect of freezing, freeze-drying and storage on inhibitory half dose ( ID50) and on cytotoxic concentration (CC50) of Phyllantus orbicularis and P unica granatum extracts was studied. Selective Index SI=(CC50/ID50) was con sidered as the antiviral criterion. Both frozen and freeze-dried extracts w ere analyzed by differential scanning calorimetry (DSC). The values of vitr eous transition temperatures of P. granatum (Tg' and Tg) were lower than th ose of Ph. orbicularis. Sorption isotherms of freeze-dried products showed a typical sigmoidal shape, where GAB model was fitted instead of BET model. Water adsorption in freeze-dried Ph. orbicularis extract was higher than i n the case of P. granatum. No significant changes in SI were induced by fre ezing or freeze-drying after a 6 months storage at -20 degreesC, but in the case of P. granatum? extract, the effectiveness was highly affected after exposure to 37 degreesC or higher.