An investigation of chemical composition and antimicrobial activity of essential oils extracted from Aeollanthus and Plectranthus species

Abstract

Essential oils from plants represent a rich source of new antimicrobials that are able to overcome the microbial virulence. The present study was designed to determine the chemical compositions and assess antimicrobial potentials of essential oils derived from Aeollanthus cucullathus (Ryding), Aeollanthus heliotropioides (Oliv.) and Plectranthus glandulosus (Hook. F.) against Candida species biofilm formation. Essential oils were extracted using hydrodistillation followed by the chemical composition determination using gas chromatography coupled with mass spectrometry (GC-MS). The minimum inhibitory concentration (MIC) was determined using a microdilution method. Then, the antibiofilm assay was performed in two stages; germ tubes and mature biofilm formation by a micro biofilm inhibition assay. Extraction yields were 0.0001%; 0.07% and 0.04%, respectively for Aeollanthhus cucullathus (ACap), Aeollanthus heliotropioides (AHap) and Plectranthus glandulosus (PGl) essential oils (EOs). The chemical analysis revealed the presence of naphthalene, 1,2,3,4,4a,5,6,8a-octahydro-4a,8-dimethyl-2-(1-methylet henyl)-, [2R-(2.alpha.,4a.alpha.,8 a.beta.)]- (6.71%), caryophyllene oxide (5.12%), 2-Isopropyl-5-methyl-9-methylenebicyclo[4.4.0]dec-1-ene (4.95%) in ACap EOs; linalool (25.67%), farnesene (13.20%), caryophyllene (6.02%) in AHap EOs and germacrene D (9.90%), (E)-3-hexenyl butyrate (9.30%), l-fenchone (8.75%) in PGl EOs. MIC values ranged from 0.31 mg/mL to 5 mg/mL respectively for AHap and PGl EOs. The inhibition of pseudo-hyphae formation revealed an activity up to 0.03 mg/mL for AHap EO on C. albicans. All the EOs inhibited the mature biofilm formation at subinhibitory concentrations. This study highlighted the possible uses of A. heliotropioides, A. cucculathus and P. glandulosus for therapeutic agent's development.