Abstract
Vaccinium dunalianum Wight, usually processed as a traditional folk tea beverage, is widely distributed in the southwest of China. The present study aimed to investigate the antioxidant, α-glucosidase and pancreatic lipase inhibitory activities of V. dunalianum extract and isolate the bioactive components. In this study, the crude extract (CE) from the buds of V. dunalianum was prepared by the ultrasound-assisted extraction method in 70% methanol and then purified with macroporous resin D101 to obtain the purified extract (PM). Five fractions (Fr. A–E) were further obtained by MPLC column (RP-C18). Bioactivity assays revealed that Fr. B with 40% methanol and Fr. D with 80% methanol had better antioxidant with 0.48 ± 0.03 and 0.62 ± 0.01 nM Trolox equivalent (TE)/mg extract for DPPH, 0.87 ± 0.02 and 1.58 ± 0.02 nM TE/mg extract for FRAP, 14.42 ± 0.41 and 19.25 ± 0.23 nM TE/mg extract for ABTS, and enzyme inhibitory effects with IC50 values of 95.21 ± 2.21 and 74.55 ± 3.85 for α-glucosidase, and 142.53 ± 11.45 and 128.76 ± 13.85 µg/mL for pancreatic lipase. Multivariate analysis indicated that the TPC and TFC were positively related to the antioxidant activities. Further phytochemical purification led to the isolation of ten compounds (1–10). 6-O-Caffeoylarbutin (7) showed significant inhibitory effects on α-glucosidase and pancreatic lipase enzymes with values of 38.38 ± 1.84 and 97.56 ± 7.53 µg/mL, and had the highest antioxidant capacity compared to the other compounds.
Highlights
Discovering bioactive compounds from natural sources is a growing research interest nowadays
The crude extract of V. dunalianum buds was purified to obtain a purified extract with phenolic enrichment through D-101 macroporous resin column chromatography
C had a higher Total Phenolic Contents (TPC) concentration (36.11 ± 0.12 mg gallic acid equivalent (GAE)/mg extract), we found that this fraction was rich in 6 -O-caffeoylarbutin (7)
Summary
Discovering bioactive compounds from natural sources is a growing research interest nowadays. Consumption of phenolics presented in food resources may reduce the risk of some chronic diseases such as abnormal cholesterol metabolism, type 2 diabetes mellitus, and hypertension [1,2]. Phenolic compounds are important natural plant secondary metabolites. They are usually classified as phenolic acids, flavonoids, tannins, lignans, and stilbene derivatives due to the structural skeletons [3]. These compounds exhibit a wide range of biological properties such as antioxidant, anti-diabetic, anti-inflammatory, anticancer, antimicrobial, and cytoprotective activities [4,5]. Attention has been focused on the phenolics, especially flavonoids, because they are able to inhibit lipid peroxidation [6]
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