Comparison analysis of bioactive constituents and heavy metals among original plants of Kuding tea from the genus Ilex

Abstract

Kuding tea (KT) is the general name of a set of bitter-tasting herbal tea made from varied original plant species. However, limited information was reported about the difference of bioactive constituents, heavy metals, and bioactivities among those original species. In the present study, comparison analyses among heavy metals, polysaccharides, phenolics, flavonoids, and saponins constituents, as well as the antioxidant and antidiabetic activities were performed through colorimetry, UPLC-QTOF-MS, enzymatic assay and molecular docking techniques on the six KT original plants mainly from the genus Ilex. Results showed that Cd contents in the four KT original plants other than Ilex pubescens (IP) and Ilex cornuta (IC) and heavy metal contents including Pb, Cu, As and Hg in the all six plants were lower than standard limit values. Furthermore, contents of carbohydrate in polysaccharides (470.06 and 548.51 mg GLE/g), total phenolics (33.84 and 48.85 mg GAE/g), flavonoids (30.86 and 109.97 mg RE/g), phenolic acids (49.68 and 61.48 mg CAE/g), flavonols (18.47 and 19.19 mg RE/g), flavanols (0.18 and 0.14 mg CE/g), saponins (90.81 and 97.33 mg GSE /g) in IP and Ligustrum japonicum (LJ), as well as their antioxidant activity levels (IC50 607.41–780.44, and 547.06–754.00 mg/L) were all significantly higher than those in other four KT original plants. Moreover, a total of 6 and 9 compounds were tentatively characterized from IP and LJ, respectively, and molecular docking and molecular dynamics simulation were further used to analysis the interaction between α-glucosidase and bioactive compounds in IP. At last, principal component, hierarchical cluster, and correlation analysis indicated that carbohydrate content of polysaccharides, total phenols, flavonoids and phenolic acids were the main influencing factors to antioxidant abilities. Overall, according to our systematic analysis, IP possessed the highest antioxidant and antidiabetic potentials, thus might be a better KT original plants from the genus Ilex for further development and utilization.

Keywords

• Kuding tea
• Heavy metals
• Phenolics
• Polysaccharide
• Antioxidant
• Antidiabetic