Bioassay-guided fractionation of a hepatoprotective and antioxidant extract of pea by-product

Abstract

Fruits and vegetables waste products offer a cheap and practical source of potent antioxidants that could be used as functional ingredients. The hydroalcoholic extract (PE) of pea (Pisum sativum L.) waste (husks) was evaluated for hepatoprotective and antioxidant activities, using CCl4-induced oxidative stress and hepatic damage in rats. PE significantly inhibited CCl4-induced elevation of serum ALT and AST by 45.3, 17.8%, respectively and normalized the levels of serum total protein and albumin in hepatotoxic rats. It afforded 31.2% protection against hepatic lipid peroxidation, recovered hepatic glutathione and protein thiols levels (by 161.3, 55.9%, respectively), restored the glutathione-peroxidase activity (by 42.7%) and significantly increased the glutathione-S-transferase activity (by 10%). PE also inhibited CCl4-induced elevation of hepatic NO levels by 34.2%. The active PE extract was fractionated using different solvents of increasing polarity and its fractions were tested for their hepatoprotective and antioxidant activities, using the same model. Chromatographic fractionation of the active n-butanol fraction led to the isolation of four flavonoid glycosides viz., quercetin-3-sophorotrioside (F1), quercetin-3-O-(6-O-feruloyl-β-D-glucopyranosyl (1→2)- β-D-glucopyranosyl (1→2)- β-D-glucopyranoside (F2), quercetin-3-O-(6-O-sinapoyl-β-D-glucopyranosyl (1→2)- β-D-glucopyranosyl (1→2)- β-D-glucopyranoside (F3) and quercetin-3-O-rutinoside (F4). The isolated compounds were quantified in PE, using a validated HPLC method. F2 (0.1312%) was the major compound, followed by F1 (0.0753%, calculated as rutin) and F3 (0.0273%, calculated as F2). Besides, low amounts of F4 (0.0049%) were also detected. According to our findings, pea by-product contained biologically active constituents which can be utilized for upgrading of this by-product to obtain high value added products for nutraceutical use.