Chemical Characterisation of Steam‐Distilled Essential Oils From Lemongrass ( Cymbopogon citratus Stapf) and Ginger Rhizomes ( Zingiber officinale Roscoe) Using FTIR and GC‐MS: Comparison of Phytochemical Composition

ABSTRACT Essential oils from lemongrass and ginger rhizomes contain bioactive compounds with potential for nutraceutical and pharmaceutical applications. In this study, essential oils were extracted from ginger rhizomes and lemongrass by the steam distillation method, using a locally fabricated extractor. The physical properties of the oils were determined, and characterisation of the oils for their phytochemical constituents and functional groups was carried out using gas chromatography–mass spectrometry and Fourier transform infrared spectroscopy. The specific gravities, refractive indices and pH values of the lemongrass and the ginger essential oils were found to be 0.878, 0.880; 1.450, 1.470; and 6.200, 6.300, respectively. It is evident from the physical properties of both oils that they contain oxygenated aromatic compounds having a specific gravity of less than 1, are slightly acidic in nature and are relatively pure in view of their refractive indices being closer to the standard values. The GC‐MS analyses showed that both essential oils have common active compounds such as citral, zingiberene, ‐curcumene, ‐bisabolene, ‐caryophyllene, ‐fernesene and citronellal, in varied compositions, which determine their antimicrobial potency. Other components identified in the lemongrass include ‐myrcene (6.95%), geraniol (0.29%), sesquiterpenoid (0.87%) and geranyl formate (0.77%), whereas those of ginger were linalool (1.13%), endo‐borneol (3.47%), eucalyptol (6.64%) and ‐terpineol (1.90%). The bioactive components of the oils obtained in this study were compared with those reported in five similar African studies. Ghana has the highest compositions, with citral and zingiberene being the principal constituents of the respective oils. The FTIR analyses confirmed the presence of aromatic compounds with conjugated double bonds (C=C), ether groups (C–O), ester groups (C=O), hydroxyl (OH) bonds of phenols and OH stretching vibrations of carboxylic acids. Based on the comparative dominance of phytochemical compounds in both oils, it is inferred that lemongrass essential oil has more potency in terms of antifungal, antibacterial, anti‐inflammatory and antiviral properties than ginger oil, whereas ginger oil is more potent in terms of antioxidant properties than lemongrass oil. Further research should be conducted on clinical trials for the treatment of illness.