engleski

Antioxidant and antimicrobial properties of the extracts from plant leaves as a potential rich sources of bioactive phenolics

By-products constitute a rich but yet underutilized source of valuable components such as phenolics, which may be applied as ingredients in the food, feed, cosmetics, and pharmaceutical industries. Special attention is focused on their extraction from inexpensive or residual sources of the food and agricultural products. Potential sources for their exploitation are plant leaves as agricultural by-products. The rising interest in the substitution of synthetic food antioxidants and antimicrobial agents by natural ones has fostered research on plant sources and the screening of new materials for identifying new substances. Phenolic compounds are secondary metabolites of plants involved in their defence against various attacks such as oxidative damage and aggression by pathogens and also potential antimicrobial agents against various pathogens. The objective of this study is to assess the efficacy of plant leaves as a residual source as antioxidants and antimicrobial agents. Polyphenols were extracted from several available leaves sources, such as Olea europaea L., Vitis vinifera (two cultivars), Morus nigra and Aronia melanocarpa and antimicrobial activity of extracts was tested against gram-positive (Staphylococcus aureus ATCC 29213, Listeria monocytogenes ATCC 19115) and gram-negative bacteria (Escherichia coli ATCC 25922, Yersinia enterocolitica ATCC 9610). Extracts were characterized by the determination of the total phenolics, the total flavonoids, DPPH and ABTS scavengers’ activity. UPLC/DAD was used for the individual phenolics determination. In general, olive, grape and mulberry leaf phenolic extracts showed strong, while chokeberry leaf phenolic extract showed moderate antimicrobial activity against selected food-borne pathogenic bacteria. All tested extracts are more effective against gram-positive bacteria. The study indicates the antimicrobial potential of these plant extracts as natural ingredients in food, cosmetics, and other products.

polyphenols; leaves; residual sources; antioxidant activity; antimicrobial activity; in vitro testing; UPLC-DAD

Potpora Sveučilišta u Rijeci br. 13.11.1.2.02