Ultrasound-assisted Extraction of Gymnemic Acids from Gymnema sylvestre Leaves and its Effect on Insulin-producing RINm-5F β Cell Lines

IntroductionGymnema sylvestre is an important anti-diabetic medicinal plant, hence it is necessary to study the effective extraction of its active medicinal components. ObjectiveTo develop an efficient ultrasound-assisted extraction method for anti-diabetic gymnemic acids from Gymnema sylvestre leaves and measure their effect on insulin-producing RINm-5F cells. MethodsBox-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-5F cell lines. ResultsThe point prediction tool of the design expert software predicted 397.9mg gymnemic acids per gram of the defatted G. sylvestre leaves using ultrasound-assisted extraction, with ethanol at 60 degrees C for 30min. 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-5F cells than extracts obtained from Soxhlet extraction. ConclusionsResponse 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. Copyright (c) 2014 John Wiley & Sons, Ltd. The ultrasound-assisted extract of G. sylvestre showed about four times more insulin production from RINm-F cells than extract obtained from Soxhlet extraction method. Percentage of ethanol in solvent influences the saponin, gymnemic acids and gymnemagenin concentration in the extract. Form scanning electron microscopy result, it was found that ultrasound treatment results in a wide opening up of tissue channels leading to more exudation of phytochemicals from plant parts.