A Comparative Study on Chemical Compositions and Biological Activities of Four Amazonian Ecuador Essential Oils: Curcuma longa L. (Zingiberaceae), Cymbopogon citratus (DC.) Stapf, (Poaceae), Ocimum campechianum Mill. (Lamiaceae), and Zingiber officinale Roscoe (Zingiberaceae)

Abstract

Essential oils (EOs) and their vapour phase of <i>Curcuma longa</i> (Zingiberaceae), <i>Cymbopogon citratus</i> (Poaceae), <i>Ocimum campechianum</i> (Lamiaceae), and <i>Zingiber officinale</i> (Zingiberaceae) of cultivated plants grown in an Amazonian Ecuador area were chemically characterised by Gas Chromatography-Flame Ionization Detector (GC-FID), Gas Chromatography-Mass Spectrometry (GC-MS), and Head Space-Gas Chromatograph-Flame Ionization Detector-Mass Spectrometry (HS-GC-FID-MS).figure The EOs analyses led to the identification of 25 compounds for <i>C. longa</i> (99.46% of the total; ar-turmerone: 23.35%), 18 compounds for <i>C. citratus</i> (99.59% of the total; geraniol: 39.43%), 19 compounds for <i>O. campechianum</i> (96.24% of the total; eugenol: 50.97%), and 28 for <i>Z. officinale</i> (98.04% of the total; α-Zingiberene: 15.45%). The Head Space fractions (HS) revealed <i>C. longa</i> mainly characterised by limonene and 1,8-cineole (37.35%) and α-phellandrene (32.33%); <i>Z. officinale</i> and <i>C. citratus</i> showed camphene (50.39%) and cis-Isocitral (15.27%) as the most abundant compounds, respectively. <i>O. campechianum</i> EO revealed a higher amount of sesquiterpenes (10.08%), mainly characterised by E-caryophyllene (4.95%), but monoterpene fraction remained the most abundant (89.94%). The EOs were tested for antioxidant, antimicrobial, and mutagen-protective properties and compared to the <i>Thymus vulgaris</i> EO as a positive reference. <i>O. campechianum</i> EO was the most effective in all the bioactivities checked. Similar results emerged from assaying the bioactivity of the vapour phase of <i>O. campechianum</i> EO. The antioxidant and antimicrobial activity evaluation of <i>O. campechianum</i> EO were repeated through HP-TLC bioautography assay, pointing out eugenol as the lead compound for bioactivity. The mutagen-protective evaluation checked through Ames's test properly modified evidenced a better capacity of <i>O. campechianum</i> EO compared with the other EOs, reducing the induced mutagenicity at 0.1 mg/plate. However, even with differences in efficacy, the overall results suggest important perspectives for the functional use of the four studied EOs.