The chemical composition of the essential oil (EO) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from the peel of grapefruit (Citrus Paradisi. L) was analysed by gas chromatography ⁄ mass spectrometry (GC ⁄ MS). Totally, twenty-five components were identified in the EO. Limonene was observed as dominant (91.5-88.6%) for two extraction methods, SFME and HD, respectively. b-Pinene (0.8-1.2%), linalool (1.1-0.7%), a-terpinene (0.7-1.0%) and the other minor components were also detected. Disc diffusion method was applied to determine the antibacterial properties of the EO. The results showed that the EO of grapefruit peel had a wide spectrum of antimicrobial activities against Staphylococcus aureus, Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Salmonella typhimurium, Serratia marcescens and Proteus vulgaris, with their inhibition zones ranging from 11 to 53 mm.

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The antibacterial activity and chemical composition of the essential oils (EOs) isolated from Origanum bilgeri P.H.Davis by two different extraction methods, i.e., hydrodistillation (HD) and solvent‐free microwave extraction (SFME), were examined. This endemic Origanum species had shown very good antibacterial activity. The composition of the O. bilgeri EOs obtained by SFME and HD was investigated by GC/MS analysis. The main components of the oils obtained by both methods were carvacrol (90.20–84.30%), p‐cymene (3.40–5.85%), γ‐terpinene (0.47–1.20%), and thymol (0.69–1.08%). The EO isolation by SFME offered many important advantages, including a higher extraction yield, a shorter extraction time, and a higher content of the active component carvacrol. The carvacrol‐rich oils obtained by both HD and SFME showed a good antibacterial activity. The largest inhibition zones were observed for the O. bilgeri EO obtained by SFME. Our study suggests that O. bilgeri EO has the potential to be used as preventative against bacterial contamination in many foods, instead of the common synthetic antimicrobial products.

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