Chemical composition and antibacterial activity of Dracocephalum kotschyi essential oil obtained by microwave extraction and hydrodistillation. (18th December 2017)

• Record Type: Journal Article
• Authors: Moridi Farimani, Mahdi; Mirzania, Foroogh; Sonboli, Ali; Moghaddam, Firouz Matloubi
• Is Part Of: International journal of food properties. Volume 20(2017)Supplement 1
• Page Start: 306
• Page End: 315
• Publication Date: 2017-12-18
• Subjects: Antibacterial activity -- Biosynthetic pathway -- Dracocephalum kotschyi -- Essential oil -- Limonene -- Microwave extraction -- Terpinyl cation -- Thermal degradation; Food -- Analysis -- Periodicals; Food -- Composition -- Periodicals; 664.0705
• DOI: 10.1080/10942912.2017.1295987
• Languages: English
• ISSNs: 1094-2912

Abstract

ABSTRACT: Dracocephalum kotschyi essential oils obtained by hydrodistillation (HD), microwave-assisted hydrodistillation (MAHD), and solvent-free microwave extraction (SFME) were investigated by GC-FID (Gas Chromatography-Flame Ionization Detector) and GC-MS (Gas Chromatography-Mass Spectrometry). The percentage of oxygenated compounds was significantly increased from 62.52% in HD to 76.47% in MAHD, and 84.52% in SFME. Conversely, the monoterpene hydrocarbons were decreased from 30.84% in HD to 13.71% in MAHD, and 5.85% in SFME. The main compound in the essential oil obtained by HD is limonene, which accounted for more than 30% of the oil, while the percentage of this compound was reduced to 9.52% in MAHD, and 5.60% in SFME. The percents of other oxygenated compounds such as neral, geranial, geraniol, geranyl acetate, α-terpineol, trans -verbenol, carvon, and trans -carveol were noticeably higher in microwave methods than those present in HD method. In aqueous medium, linear oxygenated monoterpenes may be converted to a monocyclic terpinyl cation, which it could lose a proton to give limonene. The main biosynthetic pathway of these compounds, as well as a possible route of their conversion into limonene, due to prolonged heating in the HD method, was proposed. The antimicrobial activity of D. kotschyi essential oils against Gram-positive ( Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria was evaluated by broth micro-dilution susceptibility manner. The most sensitive bacteria to these oils was found to be S. aureus with the lowest minimum inhibitory concentration value of 2 mg mL −1 for MAHD and SFME specimens. The results indicated that oils obtained by microwave methods were more active against S. aureus .