Evaluation of Antioxidant, Antimicrobial and Potential Food Preserving Properties of Rubus Discolor (Rosaceae) Fruit Extracts

Abstract

The presented study was aimed at exploring the bioactive properties (antioxidant, antimicrobial and food preserving) and chemical composition of R. discolor fruits collected from 2 geographically distinct wild-growing populations and extracted by using different solvents (methanol, ethanol, acetone and water). The total phenol (TPC), flavonoid (TFC) and anthocyanin (TAC) content varied from 52.7 to 186.8 mg GAE/g, 3.5 to 7.0 mg QE/g and 11.1 to 28.2 mg/g dry weight (dw), respectively. HPLC-DAD analysis identified cyanidin-3-glucoside (Cy-3-Glu) as the dominant anthocyanin that ranged in concentration from 18.4 to 32.2 mg/g dw. The acetone extract revealed the highest antioxidant activity through the ferric reducing antioxidant power (FRAP), total reducing power (TRC) and ß-carotene bleaching in vitro methods. The examined extracts showed antimicrobial activity, being more effective against Gram-positive (G+) than Gram-negative (G-) bacteria. Furthermore, Candida glabrata was the most susceptible among the pathogenic yeasts. The ethanol fruit extract was the most active against Listeria monocytogenes and thus chosen for incorporation in yoghurt and further analyses regarding its food preserving properties, which confirmed its efficacy towards this food-borne pathogen. Additionally, panelists gave high marks to the novel product regarding color, taste, texture flavor and overall acceptance. The obtained results indicated that R. discolor fruit extracts exhibits notable bioactivity and might therefore be considered as a good platform for the development of new preparations to be used in the food industry.