GC-MS analyses of four essential oils with antioxidant activity of extracts of Rytigynia umbellulata (Hiern) Robyns

Abstract

Article InformationEssential oil compositions of leaf, leaf stalk, stem and fruit with phytochemical screening and antioxidant evaluation of extracts obtained from Rytigynia umbellulata (Rubiaceae) were determined in this study. The essential oils were extracted using hydro-distillation method and analysed by gas chromatography coupled with mass spectrometry (GC-MS), while crude extraction was done in methanol, subjected to standard phytochemical tests and antioxidant potential of extracts was done using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The numbers of identified compounds in leaf, leaf stalk, stem and fruit essential oils were 15, 19, 27 and 11, respectively. Saturated hydrocarbons (70.95%) and acyclic diterpene (16.91%) dominate the leaf essential oil, with the most abundant being: cyclohexane (65.22%) and phytol (16.91%). Saturated hydrocarbons were also prominent in essential oils procured from the leaf stalk (67.05%), stem (37.86%) and fruit (40.32%). Carboxylic acids (11.84%) were exclusive to stalk oil, while sesquiterpenes were only identified in the stem oil. Methanol extracts from leaves (66.88 g) and stem (22.68 g) gave extractive yields of 19.11% and 4.73% respectively. Flavonoids, phenolic compounds, tannins, saponins, terpenoids and coumarins were the classes of secondary metabolites revealed in both extracts. Alkaloid was exclusive to the stem extract, while quinone was only in the leaf extract. The antioxidant evaluation showed that the stem extract exhibited better activity (IC50=0.30 mg/mL) compared to the leaf extract (IC50=0.41 mg/mL), while the control, butylated hydroxyanisole had IC50=0.19 mg/mL. The chemical compositions of the essential oils, phytochemical screening and antioxidant activity of the extracts being reported for the first time support the uses of R. umbellulata in ethno-medicine.