Chemical composition and antibacterial activity of Dracocephalum kotschyi essential oil obtained by microwave extraction and hydrodistillation

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 transcarveol 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 microdilution 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. ARTICLE HISTORY

Chemical Composition, Phytotoxic, Antimicrobial and Insecticidal Activity of the Essential Oils of Dracocephalum integrifolium

“…Essential oil obtained from another Dracocephalum species, D. foetidumby , also showed inhibitory activity against most of the tested pathogenic bacteria and yeast strains with MIC values ranging from 26 to 2592 μg/mL; furthermore, the oil was found to exhibit significant antimicrobial activity against methicilin-resistant Staphylococcus aureus (MRSA) strains, indicating this oil has potential medical value [20]. Farimani et al [14] examined the antimicrobial activity of D. kotschyi essential oils against gram-positive ( Staphylococcus aureus ) and gram-negative ( Escherichia coli ) bacteria and found S. aureus was the most sensitive strain with an IC 50 value of 2 mg/mL. Zhang et al [19] tested the antimicrobial activity of the essential oil of D. heterophyllum against nine bacterial strains, one yeast, three fungi, and found that MIC values for bacteria, yeast, and fungi strains were 0.039–0.156, 0.156, and 0.313–2.500 mg/mL, respectively.…”

“…A literature survey of the chemical composition of essential oils produced by Dracocephalum plants revealed the presence of remarkable variations among their major constituents [12]. These oils were found to possess various biological activities such as antimicrobial [13,14,15,16,17,18,19,20], antioxidant [13,17,19,21,22,23], insecticidal [24,25], phytotoxic [26,27], cytotoxic [17], antispasmodic [28] and antinociceptive [29] activity.…”

Medicinal Properties and Active Constituents of Dracocephalum kotschyi and Its Significance in Iran: A Systematic Review

“…Solvent polarity plays an important role in extraction of phenolic compounds. In this regard, methanol was a better solvent in extraction of phenolic compounds [71]. The quantity of luteolin in D. kotschyi was found to be 1061.005 μ g/g of dried plant.…”

Volatile Compounds, Chemical Composition and Biological Activities of Apis mellifera Bee Propolis

“…The basic principle of this type of extraction is azeotropic distillation (substances behave as if they were pure in relation to the boiling point), and to occur, a heating source, a container to place the vegetal biomass (for example, a volumetric flask), a condenser, and a decanter for collecting the oil and water mixture are necessary. HD is considered a multilateral method and, although simple, can be used in small or large industries because of its selectivity and low installation cost [20,23,24]. Hydrodistillation process is originated in alembics, however, since the third edition of the European pharmacopeia, its use along with the modified Clevenger system has been recommended, as this system enables the condensate recycling [20].…”