Optimization of terpene lactones and ginkgolic acids extraction from Ginkgo biloba L. leaves by natural deep eutectic solvents using experimental design and HPTLC-MS analysis

In this work, a green extraction method was investigated to maximize the yield of terpene lactones and minimize that of ginkgolic acids from Ginkgo biloba L. leaves. An HPTLC-MS method for identification of simultaneous determination of terpene trilactones and ginkgolic acids in G. biloba samples was developed and validated. The limit of detection is 0.791, 0.850, 0.868, 0.785, 0.763, 0.871 and 0.622 μg/band, whereas the limit of quantitation is 2.399, 2.576, 2.632, 2.380, 2.313, 2.640 and 1.885 μg/band for bilobalide, ginkgolide A, ginkgolide B, ginkgolide C, ginkgolide K, ginkgolide J and ginkgolic acid, correspondingly. The extraction ability of 15 different mixtures of NADES, using ultrasonic assisted extraction in comparison to methanol, ethanol and water was tested. The results revealed that DES2 (Choline chloride, ascorbic acid) displayed the highest extraction yields of total ginkgolides. Concerning ginkgolic acids, in comparison with conventional solvents, DES 2 displayed significantly lower extraction amounts. Optimization experiments using Box Behnken design indicated that the ginkgolides extraction yield was highly affected by water percentage (C, p < 0.0001; C2, p < 0.0001) followed by ultrasonication temperature (B, p < 0.0001; B2, p < 0.0001), while ultrasonication temperature possessed stronger influence on extraction yield of ginkgolic acids. The set optimum conditions for extraction were found to be an ultrasonication time of 36.63 min, temperature of 55.77 °C and a water content of 33.66% v/v.