Phenolic profile, antioxidant and antimicrobial activity of oregano (Origanum vulgare L, Lamiaceae) postdistillation waste extracts

Abstract

Aromatic herbs have long tradition of use in medicine, nutrition and cosmetics. Among them, oregano (Origanum vulgare L, Lamiaceae) has been appreciated as a spice and food flavouring agent owing to the presence of essential oil. However, postdistillation waste, remaining after the isolation of essential oil, is still unused. Thus, in this study antioxidant and antimicrobial activity of oregano herb postdisillation waste material was investigated. After the hydrodistillation of essential oil of oregano herb, postdistillation waste material extracts were made from decoction and used herb (with 45% v/v and 75% v/v ethanol). Chemical composition was determined by means of high performance liquid chromatography. In vitro scavenging activity was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazile) (DPPH) and hydroxyl (OH) radical. The effect on the peroxidation of membrane lipids was assayed by thiobarbituric acid (TBA) test, following the effect of investigated extracts on Fe2+/H2O2induced lipid peroxidation (LP) in corn oil as a model system. Minimal inhibitory concentration (MIC) was determined with broth microdilution assay against selected gram-positive (Staphylococcus aureus and Bacillus cereus) and gram-negative bacteria (Salmonella Infantis, Escherichia coli). All investigated extracts were rich in phenolcarboxylic acids (rosmarinic, protocatechuic, gallic and chlorogenic acid) and flavonoids (rutin and apigenin). They exhibited strong antioxidant and antibacterial activity (especially extract obtained with 75% ethanol from used herb) when compared to standardised oregano herb extract. This study confirms postdistillation plant waste material for possible use in pharmaceutical and food industry and gives very informative insight into antioxidant and antibacterial profile of investigated oregano extracts.