Reclamation of beneficial bioactivities of herbal antioxidant condensed tannin extracted from Euonymus laxiflorus

Abstract

Natural condensed tannins (CT) have received great interest due to their vast beneficial bioactivities. Recently, Euonymus laxiflorus, an edible medicinal herb collected in the Central Highlands of Vietnam, was newly recognized as a natural source rich in antioxidant CT. The aim of this study is to scale up extraction and investigate various novel bioactivities of the isolated CT. The screening of the parts used rich in CT, such as heartwood, trunk bark, branch, and the leaves of EL, indicated that the EL trunk bark (ELTB) has the highest CT content. E. laxiflorus CT (ELCT) was extracted with high-level scale from ELTB via several techniques and then was qualified by NMR spectra and HPLC finger printing. A condensed tannin ELBT-3.1.d was isolated and showed its high molecular weight of ≥ 10 kDa and various in vitro bioactivities. ELBT-3.1.d demonstrated high antioxidant capacity (IC50 = 6.11 µg/mL), and potent enzymes inhibition targets in anti-diabetes, especially showing novel potential inhibition against human salivary α-amylase with IC50 value of 3.01 µg/mL. ELBT-3.1.d displayed no anti-NO effect but did show moderate to effective anticancer activities against A549, MCF-7, HepG2, and WiDr. Notably, condensed tannin ELBT-3.1.d displayed no toxicity to normal cells and a novel potential prebiotic effect on Lactobacillus paracasei BCRC14023 and Lactobacillus rhamnosus BCRC16000. In the animal test, ELCT demonstrated significant effect on reducing plasma glucose in mice at the doses of 50–100 mg/kg BW. The current study contributes to enrich the novel bioactivities of ELCT which may be suggested as functional food or drugs due to processing numerous beneficial bioactivities.