Stability studies of saponins in 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 the extract components, especially on the lead compound important for pre-formulation, have not yet been reported. In this study, the stabilities of the crude extract and the diluted crude extract were investigated at various temperatures using saponin glycosides, bacopaside I and bacoside A₃ as markers for quantitative analysis. The stability testing of bacopaside I and bacoside A₃ standard solution was performed at various temperatures and pH values. The quantity of both compounds under all conditions was analyzed using HPLC techniques. The moisture adsorption of the crude extract was determined at 5, 40, 60 and 80°C at 75% relative humidity using gravimetric methods. The results revealed that the crude extract quickly adsorbed moisture up to 54% w/w at both 40 and 80°C, while it only slowly adsorbed moisture at 5 °C. The amounts of intact bacopaside I and bacoside A₃ 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 both compounds in the standard solution dropped sharply at a pH of 1.2 but slowly at pH 6.8 and 9.0, respectively. The pre-formulation data could be further used for improvement of the final product quality.