Eremomastax speciosa (Hochst.): GC/MS profiling, antioxidant and antimicrobial activities of stem essential oil

Abstract

Abstract Background Eremomastax speciosa (Hochst.) Cufod. (Acanthaceae) is a renowned medicinal plant used to ease menstrual cramps and treat female infertility, anaemia, dysentery, urinary tract infection and haemorrhoids. Essential oils and their constituents from herbs have also been utilised in the management of a good number of ailments in ethno-medicine. The chemical composition, antioxidant and antimicrobial activities of the stem essential oil are investigated in this study. The essential oil was obtained by hydro-distillation using an all-glass Clevenger apparatus. Identification and characterisation were done using Gas Chromatography–Mass Spectrometry, while antioxidant activity was evaluated with 2, 2-diphenyl-1 picrylhydrazyl radical (DPPH*) method. The antimicrobial property was assessed by the broth dilution method. Results The essential oil contained forty-three compounds constituting 62.87% of the total oil composition. It was dominated by non-terpene derivatives, of which (14β)-Pregnane (17.58%) is the most abundant compound. Other significant compounds identified in the essential oil include n-decane (2.3%), norbornane (2.2%), (−)-α-Copaene (1.5%), 10-epizonarene (1.5%), thymol (1.25) and (−)-α-phellandrene (1.12%). The essential oil exhibited significant antioxidant activity (IC50 0.7296 μg/mL), which is more active than the standards; vitamin C (IC50 0.8728 μg/mL) and butylated hydroxy anisole (IC50 0.8729 μg/mL) used for the assay. Also, the oil inhibited significant bacterial and fungal strains at concentrations ranging from 100 to 3.125 μg/mL with a minimum inhibitory concentration between 3.5 and 6.5 μg/mL. Conclusion The chemical composition of the stem essential oil of E. speciosa could be responsible for the pharmacological applications of the plant in ethno-medicine and the chemical constituent of the stem essential oil of E. speciosa is reported for the first time. Graphical Abstract