Enrichment of citral isomers in different microwave-assisted extraction of essential oil from fresh and dried lemon verbena (Aloysia citridora ) leaves

Abstract

Solvent‐free microwave extraction (SFME) and microwave‐assisted hydrodistillation (MAHD) were utilized for extraction of lemon verbena essential oil (EO) in comparison with the conventional hydrodistillation (HD). Chemical composition, extraction yield, physical properties, operation cost, antioxidant activity, and antifungal activities of extracted EOs were measured. Final yields of extraction and physical properties of extracted EOs did not show any significant difference among the three methods, but the required extraction time for extraction by microwave‐assisted extraction (MAE; i.e., MAHD and SFME) methods improved to a shorter time span. Even though the compounds in all three extraction techniques were exactly similar, extraction by MAE methods, especially the SFME, increased the quantity of oxygenated compounds such as citral isomers (geranial and neral) in comparison with HD. The obtained results showed that MAE methods, especially SFME, can selectively extract oxygenated compounds such as citral isomers and improve antioxidant and antifungal activities of the extracted EOs. Practical applications Oxygenated compounds like citral isomers are mostly effective in treating many health disorders. According to the results of this study, microwave extraction like MAHD and SFME result in the enrichment of citral isomers of EOs. This selective extraction can affect antioxidant and antifungal activities of EOs extracted by the microwave method in comparison with conventional methods like HD.

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“…Recently, it was demonstrated that citral produces a long-lasting inhibition of TRPV1-3 and TRPM8 channels, whereas it produces a transient block of both TRPV4 and TRPA1 channels. Similarly, it was demonstrated that the main constituent of the fruit essential oil of C. insularimontanum is citral, and that this compound exerted a significant inhibitory effect on the production of nitric oxide in lipopolysaccharide-stimulated RAW 264.7 cells 12 . Moreover, citral exhibited an anti-inflammatory effect in a test of croton oil-induced mice ear edema.…”

Thin layer drying kinetics of lemon verbena leaves: a quality assessment and mathematical modeling

“…Essential oil extraction was carried out by the hydro-distillation method. In this method, 15 g of dried lemon verbena was crushed at first and then hydro-distilled in a round bottom flask including 300 mL of deionized water for 2 hours by using an electromantle heater (EM2000/C, Electrothermal Engineering Ltd., UK, 335 W) equipped with Clevenger apparatus (Basti et al, 2007;Golmakani et al, 2017). The apparatus included a round bottom flask, condenser, essential oil collector, return section and electric heater.…”

“…For this purpose, a gas chromatography (Agilent Technologies 7890A, USA) in conjunction with a mass spectrometer (Agilent Technologies 5975C, USA), operating at 70 eV ionization energy, 0.5 s/scan, and a mass range of 35-400 amu, equipped with an HP-5MS capillary column (phenylmethyl siloxane, 30 m 3 0.25 mm ID; 0.25 lm film thickness), were used. Details of the GC-MS method are described in Golmakani et al (2017).…”

Optimisation of Sequential Microwave-Assisted Extraction of Essential Oil and Pigment from Lemon Peels Waste

“…It is known that EOs are volatile, soluble in organic solvents but insoluble in water at room temperature [ 3 ], and they can be used as flavours and aromatic ingredients in food preservatives and cosmetics or therapeutic agents in biomedical applications [ 4 ]. Besides, different terpenoids mainly present in EOs (monoterpenes such as citral, pinene, or terpinene, as well as poly(methoxyflavones) and furanocoumarins), have been used since ancient times to treat a variety of health diseases, such as spasms, fever, respiratory problems, cardiovascular diseases, gastrointestinal problems or anxiety [ 5 ]. Several works have demonstrated the antimicrobial performance of EOs against pathogenic bacteria and fungus strains [ 6 , 7 , 8 , 9 ].…”

“…MAHD was used to obtain the EO from lemon verbena leaves, improving the selectivity of oxygenated compounds, such as citral isomers, compared to conventional HD. Besides, the antioxidant and antifungal activities against nine species of fungi isolated from contaminated Feta cheese were evaluated, obtaining successful results in terms of growth inhibition [ 5 ]. Dao et al obtained a yield of 0.76 wt.% for the extraction of the EO from lemon leaves using MAHD [ 3 ].…”