Phenolic constituents from apple tree leaves and their in vitro biological activity

Abstract

Apple (Malus domestica Borkh.) leaves are good source of polyphenols. Considering the increasing demand of such phytochemicals, particularly in healthcare sector, the objective of this study was to evaluate the bioactivity of apple leaves phenolics. Different solvent mediated extracts obtained from the apple leaves were assessed for presence of phenolic compounds. Among different extracts, the highest phenolic content of 30.38±0.50mg/g were recorded in 70% aqueous ethanol (ALE-7) with subsequent high antioxidant value (IC50 49.16μg/mL) by ABTS assay. RP-HPLC-DAD phenolic profiling of leaves extract, irrespective of solvent used for extraction, revealed presence of five major compounds with maximum yield of phloridzin (24.43±0.05mg/g), followed by quercitrin (2.06±0.05mg/g), quercetin-3-O-glucoside (1.55±0.001mg/g), epicatechin (0.37±0.07mg/g) and phloretin (0.15±0.05mg/g). ALE-7 extract was further fractionated with hexane (ALH) and ethyl acetate (ALEA), which were evaluated for their in vitro biological activities. ALEA extract exhibited higher nitric oxide (NO) scavenging activity (63.3%) at 200μg/mL. This fraction also showed maximum lymphocyte proliferation (34%) at 25μg/mL after 48h. The antimicrobial testing of isolated fractions revealed that ALH fraction (MIC value ranging from 1.18–2.37μg/mL) could be a good candidate, especially for controlling food borne pathogen. Furthermore, the in vitro cytotoxicity assessment of different apple leaves fractions was also performed against human cancer cell lines (KB, SiHa and A-549), but none of the fraction was found cytotoxic against selected cell line. In conclusion, the presence of biologically active phenolics in apple leaves makes it a feasible renewable bioresource for extraction of such phytochemicals for the development of nutraceuticals particularly against inflammation and microbial infections.