Active Constituent in the Ethyl Acetate Extract Fraction of Terminalia bellirica Fruit Exhibits Antioxidation, Antifibrosis, and Proapoptosis Capabilities In Vitro

Abstract

Terminalia bellirica (Gaertn.) Roxb. fruit (TBF) is a widely planted traditional medicinal herb in Tibet. We aimed to determine the most active substance-enriched extract by comparing the in vitro antioxidant activities of different extract fractions of TBF that were subsequently extracted by petroleum ether, chloroform, ethyl acetate, and n-butanol after initial extraction by 95% ethanol. The main compounds of the ethyl acetate extract fraction (EF) were analyzed via HPLC-MS. Gallic acid (GA) was obtained from EF to determine in vitro antifibrotic activity based on the traditional usage of TBF. After HSC-T6 cells were incubated with GA, extracellular secreted levels of fibrosis-associated cytokines, such as collagen I, collagen III, TGF-β1, and hydroxyproline, were estimated by ELISA. Gene and protein expressions of PDGFR, CTGF, NF-κB, MMP-2, TIMP-1, TIMP-2, α-SMA, and the Bcl-2/Bax family were determined by quantitative PCR and western blot. The proapoptotic effect of GA was further investigated by annexin V-PI and TUNEL staining. These results indicate that EF has prominent in vitro antioxidant activity among four extract fractions, and its main component, GA, manifests antifibrosis activity and its potential mechanism of action includes inhibition of cytokine secretion and collagen synthesis, as well as proapoptosis of HSCs.