Ultrasound-assisted extraction of gymnemic acids from Gymnema sylvestre leaves and its effect on insulin-producing RINm-5 F β cell lines.

INTRODUCTION: Gymnema sylvestre is an important anti-diabetic medicinal plant, hence it is necessary to study the effective extraction of its active medicinal components.

OBJECTIVE: To develop an efficient ultrasound-assisted extraction method for anti-diabetic gymnemic acids from Gymnema sylvestre leaves and measure their effect on insulin-producing RINm-5 F β cells.

METHODS: Box-Behnken's design and response surface methodology was applied to the ultrasound-assisted extraction of gymnemic acids from Gymnema sylvestre leaves. Analysis of gymnemic acids was carried out by high-performance thin-layer chromatography by converting total gymnemic acids into gymnemagenin by alkali hydrolysis. Effects of extracts on insulin production were tested on cultured, insulin-producing RINm-5 F β cell lines.

RESULTS: The point prediction tool of the design expert software predicted 397.9 mg gymnemic acids per gram of the defatted G. sylvestre leaves using ultrasound-assisted extraction, with ethanol at 60 °C for 30 min. The predicted condition shows 93.34% validity under experimental conditions. The ultrasound-assisted extract caused up to about four times more insulin production from RINm-5 F β cells than extracts obtained from Soxhlet extraction.

CONCLUSIONS: Response surface methodology was successfully used to improve the extraction of gymnemic acids from G. sylvestre leaves. The ultrasound-assisted extraction process may be a better alternative to prepare such herbal extracts because it saves time and may prevent excess degradation of the target analytes.