Phenolic Content and Antioxidant Activity of a Raspberry Leaf Dry Extract

Polyphenols are known for their beneficial effects towards chronic disease caused by oxidative stress (diabetes mellitus, cancer, atherosclerosis). In the present study, a raspberry (Rubus idaeus L.) leaf dry extract was evaluated for its phenolic content and antioxidant activity. Spectrophotometric and HPLCUV/HPLC-MS methods were used for polyphenols determination and 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’ -azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS• +), ferric reducing ability (FRAP), oxygen radical absorbance capacity (ORAC) methods for antioxidant activity. 2’,7’dichloro-dihydrofluorescein diacetate (DCFH-DA) assay was used to investigate the cytoprotective effect against oxidative stress in human HepG2 cell line. It was found that the extract is a rich source of flavonoids and phenolcarboxylic acids (43.08 mg% quercitrin, 14.33% isoquercitrin, 43.40 mg% p-coumaric acid, 17.51 mg% caffeic acid, 11.41 mg% ferulic acid, 220.26 mg% quercetin) and has a modest antioxidant activity (EC50 = 0.0991 mg/mL - DPPH assay, EC50 = 0.2274 mg/mL - ABTS• +, EC50 = 0.0682 mg/mL - FRAP and 7243.7 μM trolox/g - ORAC) compared with standards (ascorbic acid, gallic acid). The dry extract showed a dose-response antioxidant activity against alloxan, induced oxidative stress inHepG2 cells, with a maximum effect at 0.01 mg/mL. Due to its phenolic content, the extract might be used for hepatic disorders treatment, associated with oxidative stress.