Volatile compounds and biological activity of the essential oil of Aloysia citrodora Paláu: comparison of hydrodistillation and microwave-assisted hydrodistillation

Aromatic plants are a remarkable source of natural products. Aloysia citrodora Palau (Verbenaceae), commonly known as lemon verbena, is a relevant source of essential oils with potential applications due to its lemony scent and bioactive properties. Studies carried out on this species have focused on the volatile composition of the essential oil obtained by Clevenger hydrodistillation (CHD), with little information available on alternative extraction methodologies or the biological properties of the oil. Therefore, this work aimed to compare the volatile composition, antioxidant activity, cytotoxicity, anti-inflammatory and antibacterial activities of the essential oil extracted by conventional hydrodistillation by Clevenger (CHD) and Microwave-Assisted Hydrodistillation (MAHD). Significant differences (p < 0.05) were observed for some compounds, including the two major ones, geranial (18.7-21.1%) and neral (15.3-16.2%). Better antioxidant activity was exhibited by the MAHD essential oil in DPPH radical scavenging and reducing power assays, while no differences were observed in the cellular antioxidant assay. The MADH essential oil also presented higher inhibition against four tumoral cell lines and exhibited lower cytotoxicity in non-tumoral cells as compared with Clevenger-extracted essential oil. In contrast, the latter showed higher anti-inflammatory activity. Both essential oils were able to inhibit the growth of eleven out of the fifteen bacterial strains tested. The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for providing financial support through national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020), CeDRI (UIDB/05757/2020 and UIDP/05757/2020) and SusTEC (LA/P/0007/2021); the national funding by FCT, P.I., through the institutional and individual scientific employment program—contract for R.C.C. (CEECIND/01011/2018) and PhD grant for Rafael Mascoloti Spréa (2020.08092.BD); the MICINN for the Juan de la Cierva Formación contract for T.C.S.P.P. (FJC20120-045405-I); and the “BIOMA—Bioeconomy integrated solutions for the mobilization of the Agro-food market” (POCI-01-0247-FEDER-046112) project, financed by the European Regional Development Fund (FEDER) through the Incentive System for Research and Technological Development within the Portugal 2020 Competitiveness and Internationalization Operational Program.