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

Abstract

The post-distillation residues of essential oil from medicinal and aromatic plants represent 98% of the raw material and can be utilized as natural sources of bioactive compounds with various types of bioactivities. This work aims to evaluate the effect of three extraction methods on the total polyphenol content and the antimicrobial activity of the phenolic extracts obtained from these residues. The total polyphenol content (TPC) was evaluated using the Folin-Ciocalteau method, and the antimicrobial activity was assessed using disk diffusion and dilution methods of the extracts obtained with three methods: maceration (M), ultrasound and maceration (US+M), and ultrasound (US) against Escherichia coli and Bacillus subtilis ranging from 31.25 to 500 mg/L. The M extracts showed the highest total polyphenol content (7911 ± 51 GAE mg/mL), while the highest antimicrobial activity was observed against E. coli. The minimum inhibitory concentration for E. coli was 500 mg/L, and for B. subtilis, it could not be determined within the study range. The experimental findings pointed to the potential use of post-distillation residue extracts of rosemary essential oil as antimicrobials in foods susceptible to E. coli.