Studies on use of heat in the aqueous extraction of miswak

Introduction: The antimicrobial properties of Miswak (Salvadora persica) are well documented, and the use of its extracts in the formulation of toothpastes and mouth rinses are well established. Most of the literature agrees that the organic extracts are more effective than aqueous extracts. Aims: The aim of the study was to prepare aqueous Miswak extracts using three different methods. The difference between the methods is the amount of heating used for their preparation. Furthermore, to evaluate stability during storage of such extracts, their pH, and their antimicrobial activity. Materials and Methods: Miswak extracts were prepared by maceration, infusion, and decoction methods, followed by evaluation of their extraction efficiency, stability, pH, viscosity, and antimicrobial activity. Results: A correlation was found between pH of extracts and their viscosity. The pH of extract increases to 6.5 when extensive heat was used during preparation, which is close to the normal pH of saliva and oral cavity. The accompanied increase in viscosity was an indication of increased extraction efficiency. Suppression of freezing point confirmed such observation for extracts prepared by decoction. The only positive antibacterial activity was observed for decoction extract, but it was less than that of chlorhexiden. For minimum inhibitory concentration estimation, it was found that almost 50% w/v of the extract must be used to provide the minimum microbial inhibitory effect. Conclusions: Miswak components appear to be thermostable ingredients, and the method of decoction can produce stable and effective Miswak extract.