Quality evaluation of the exsiccated alum

Abstract

Alum, an elemental medicinal material popularly used in Thai traditional medicine, consists of two chemicals: potash alum and ammonium alum, both of which have astringent medical properties for topical and oral administrations. However, the alum that has been used in a certain Thai herbal preparation must be specially heated by the unique method called “Satu”. The aims of this study were to evaluate the quality of the alum exsiccated with the conventional method and to identify the type of alum salt. As a result of the chemical analysis, the exsiccated alum samples obtained from the market were ammonium alum. After heating or exsiccation, the amounts of ammonium salt, water-insoluble substances, alumina, iron, arsenic, copper, zinc and calcium in the exsiccated alum were larger than in the unexsiccated alum. The pH values of alum and exsiccated alum were 3.47 and 3.54, respectively. After exsiccation, the alum’s weight was lost by 53.65±0.55% (n=18). In conclusion, due to the loss of water during exsiccation, the amounts or proportions of mineral compounds especially iron in the exsiccated alum increased five-fold. The results have displayed the scientific evidence of the Thai traditional medicine knowledge in using exsiccated alum in Thai herbal preparations; and the “Satu” process has been practised in the herbal drug preparation. Additionally, the chemical properties of exsiccated alum available in the market are similar to those of raw alum, probably due incomplete heating or improper storage. Thus, it is suggested that exsiccated alum should be kept in a tightly closed container to protect against moisture.