Phytochemical, Antioxidant and Free Radical Scavenging Activities of Ethanol Extract of Costus afer, Sida acuta and Irvingia gabonensis

Background: Scientific investigation supporting the use of various African plant species for the management of diseases, including neurological disease is currently ongoing. Plant-based antioxidants have recently received a lot of attention because of their purported positive impact on human health. Medicinal plants selected for this study are widely used in traditional medicine for the treatment of neurological disorders. Aims: This study investigated the phytochemical, antioxidant and free radical scavenging activities of ethanol leaf extracts of Costus afer, Irvingia gabonensis and Sida acuta. Materials and Methods: Fresh leaves of Costus afer, Irvingia gabonensis and Sida acuta were collected from a farm at Egbu in Owerri North LGA of Imo state. They were washed and spread to air dry at room temperature and ground into fine powder. Phytochemistry was carried out through gas chromatography coupled with mass spectrometry (GC-MS) analysis. Fourier transform infrared (FTIR) spectroscopy was used to determine the functional groups in the plant extracts. The in vitro antioxidant activity was determined for total flavonoid content (TFC) and total phenol content (TPC). Free radical scavenging potential was evaluated by measuring 2, 2-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant potential (FRAP), nitric oxide (NO), and hydroxyl (OH) radicals. Results: A total of thirty-seven (37) phytocompounds were revealed in Costus afer, while Irvingia gabonensis and Sida acuta exhibited sixty-seven (67) and ninety-four (94) phytocompounds respectively. Bioactive compounds such as flavonoids, alkaloids, phenols, carboxylic acids, fatty acids, alkenes, glycosides, steroids, alcohol, and aldehydes were present in the plant extracts. The functional groups present in the extracts included disubstituted aromatic compounds, phenols, alkenes, aromatic amines, isothiocyanates, phosphonic acids, amine salts, secondary amines, phosphines, carboxylic acids, aldehydes, intramolecular bonded alcohols, aromatic esters and free alcohols. Sida acuta extract exhibited the highest levels of total flavonoid (9.29 ± 0.23 mg/ml) and phenolic content (6.15 ± 0.15 mg/ml). All three samples exhibited statistically significant (p<0.05) values for DPPH, FRAP and OH scavenging activities. Conclusion: The results suggested that the ethanol leaf extracts of Costus afer, Sida acuta and Irvingia gabonensis had considerable number of phytochemicals, antioxidant and free radicals scavenging properties, hence supporting the traditional use of the plants in the management and treatment of neurological disorders.