Comparison study for the recovery of bioactive compounds from Tribulus terrestris, Panax ginseng, Gingko biloba, Lepidium meyenii, Turnera diffusa and Withania somnifera by using microwave-assisted, ultrasound-assisted and conventional extraction methods

Abstract

Heat reflux (CONV), Soxhlet (SOX), microwave-assisted (MAE) and ultrasound-assisted (UAE) extraction methods, using ethanol, water and their mixtures, were studied for the recovery of bioactive compounds from Tribulus terrestris, Panax ginseng, Gingko biloba, Lepidium meyenii, Turnera diffusa and Withania somnifera. The study revealed that SOX method achieved extracts with the highest yieldTPC in terms of the total phenolic content (TPC) (66.65 ± 1.50%); MAE and UAE resulted also in extracts with high TPC and shorter treatment times compared to SOX. More specifically, the TPC values for MAE and UAE were 91.783 ± 0.026 mg GA/g dw and 81.113 ± 0.103 mg GA/g dw, respectively, the antioxidant activity (DPPH) was 63.577 ± 0.057 mg Trolox/g dw and 64.923 mg Trolox/g dw, and the yieldTPC was 60.82% and 61.89%, respectively. All were higher compared to those obtained by the CONV method. The use of pure ethanol as the extraction solvent, provided maximum TPC and similar results for DPPH and yieldTPC (%). Moreover, maximum TPC (183.70 mg GA/g dw) and DPPH (377.21 mg Trolox/g dw) values were achieved for T. diffusa. The HPLC analysis of T. terrestris, P. ginseng and G. biloba extracts showed that G. biloba contained its characteristic bioactive compound in the highest concentration (13.512 mg gingkolide/g herb).