Antioxidant properties, anti-nutritive and toxic factors of Terminalia sericea in Onderstepoort

Anti-nutritive and toxic factors in plants adversely affect animal health and production. Hence, the aims of the study were to (1) carry out qualitative and quantitative analysis of these factors in Terminalia sericea that grows abundantly in Onderstepoort; (2) evaluate an affordable, efficient and reliable method that reduces these factors and (3) evaluate antioxidant properties of the phenolic compounds. Thus, sequential organic and aqueous extractions were carried out on T. sericea leaves and feed pellets. Extracts were subjected to qualitative analysis to confirm the presence of 11 phytochemicals. While quantitative analysis of nine phytochemicals was carried out on spectrophotometry, the phenolic extracts were further tested for antioxidant activity on 2,2-diphenyl-picrylhydrazyl (DPPH) assay where gallic acid (GA), quercetin (Q) and ascorbic acid (AA) were used as standards. The contents of GA, Q and AA in the phenolic extracts were determined on high-performance liquid chromatography (HPLC). Aqueous extraction was an effective method as most phytochemicals were extracted. Nine phytochemicals were qualitatively analysed in T. sericea. The highest contents of 1.97% and 2.37 ± 0.077 mg/g gallic acid equivalent with a significant difference (p < 0.05) were determined in oxalates and phenolics, respectively. Furthermore, 83.1% DPPH inhibition (IC₅₀ = 0.0432 μg/mL) was determined relative to the standards (85.27% – 85.96%; IC₅₀ = 0.000009 μg/mL – 0.00042 μg/mL). Subsequently, HPLC results showed that T. sericea contained high concentration of AA (62.5 ± 2.13 μg/mL) to confirm antioxidant properties of the leaves. Contribution: Though T. sericea leaves have antioxidant activities, the alkaloid contents may pose a threat to the livestock. Therefore, farmers around Onderstepoort should protect their livestock from feeding on these leaves.