Antimicrobial bioactivity of the phenolic extract assisted by ultrasound from the solid waste post-distillation of essential oil of Origanum vulgare

Abstract

The post-distillation residues of essential oil from medicinal and aromatic plants, such as oregano, are potential sources of natural polyphenols. The solid residues from the essential oil industry are produced in significant volumes and can be used as natural sources of bioactive compounds. Therefore, this work was designed to evaluate the effect of three extraction methods on the total polyphenol content and the antimicrobial activity of the phenolic extracts obtained from post-distillation solid residues. The total phenolic content (TPC) and the antimicrobial activity of the extracts obtained by three methods were evaluated: maceration (M), ultrasound and maceration (US+M), and ultrasound (US) against Escherichia coli and Bacillus subtilis at concentrations ranging from 625 to 5000 mg/L. The ultrasound (US) extracts showed the highest total phenolic content (13000 mg/L gallic acid equivalents, GAE), while the minimum inhibitory concentration (MIC) of the rosemary essential oil extract (RPAEO) for E. coli was found to be 5000 mg/L in all three extraction methods, and for B. subtilis it was 5000 mg/L with the US+M and US extracts and 2500 mg/L with the M extract. The experimental findings pointed to the potential use of post-distillation oregano essential oil residue extracts as antimicrobials in the food industry, in addition to being rich sources of phenolic compounds.