Stability studies of saponins from Bacopa monnieri dried ethanolic extracts

Bacopa monnieri (L.) Wettst. (Brahmi) is currently used as a drug and food supplement for memory improvement. However, studies on the physical and chemical stability of its active saponin components, jujubogenin and pseudojujubogenin glycosides have not yet been reported. In this study, the stability of bacoside A 3 and bacopaside I the major jujubogenin and pseudojujubogenin glycosides in Brahmi were investigated. The studies were conducted in crude semi-solid extract, crude extract solution and pure compound solution at various temperatures and pH values were studied. The quantities of both compounds in all conditions were analyzed using HPLC techniques. The moisture adsorption of the semi-solid crude extract was determined at 5, 40, 60, 80°C at 75% relative humidity using the gravimetric method. The results revealed that the crude extract quickly adsorbed moisture up to 54% w/w at 40 and 80°C, while it adsorbed moisture only slowly at 5°C. The amount of both compounds in the crude extract decreased drastically at 80°C, slowly at 40 and 60°C, and remained unchanged at 5°C during the period of investigation. Moreover, the amount of intact compounds in the solution form dropped sharply at a pH of 1.2 but slowly at pH 6.8 and 9.0, respectively. In conclusion, saponins in Brahmi extracts were not stable at high temperature and low pH. Saponins were more stable in the semi-solid crude extract than in crude extract solution and pure compound solution forms. The pre-formulation data could be further used for improvement of the final product quality.