Abstract
ABSTRACTDracocephalum 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.
Highlights
The genus Dracocephalum, belonging to the Lamiaceae family, is represented in Iran by eight species.[1]
We investigated the chemical composition of D. kotschyi oil obtained by microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME)
D. kotschyi essential oils obtained by HD, MAHD, and SFME were investigated by capillary GC and GC-MS
Summary
The genus Dracocephalum, belonging to the Lamiaceae family, is represented in Iran by eight species.[1] Dracocephalum kotschyi is one of the important endemic species and is distributed in many parts of Iran.[2] It is locally known as Badrandjboie-Dennaie or Zarrin-giah, and the aerial parts of the plant have been used as an additive to improve the taste and scent of tea and yogurt. In Iranian folk medicine, the plant is used as a remedy for stomach disorders. Its usefulness for headache, congestion, and liver disorders has been described in traditional medicine documents.[3] It is one of the constituents of Spinal-Z, a traditional Iranian anticancer remedy, which was used by traditional healers as a plant concoction for the treatment of many forms of cancer in humans.[4] Pharmacological studies have confirmed some medicinal properties of the plant, including antihyperlipidemic,[5] immunomodulatory,[6] antinociceptive,[7] and cytotoxic[8]
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