ANTIOXIDANT ACTIVITY OF AFRICAN BLOOD TONIC (Eremomastax speciosa) AND AFRICAN PADAUK (Pterocarpus soyaxuii) LEAVES AFTER SIMULATED DIGESTION AND THEIR ANTI-DIABETIC POTENTIAL IN VITRO

Abstract

Medicinal plants are natural products endowed with tremendous capacities to treat wide arrays of diseases. The use of plant-based formulation to treat diseases also known as herbal medicine is the oldest form of medicine. This present investigation was aimed at examining the antioxidant indices (total phenol, total flavonoids content, ferric reducing antioxidant power, α-α-diphenyl-β-picrylhydrazyl, 2,2’-azino-bis-3-ethylbenzothiazoline and hydroxyl anti radical actions) and antidiabetic potential (α-amylase, α- glucosidase, non-enzymatic glycosylation of haemoglobin, yeast glucose uptake rate and glucose diffusion inhibitory effect) of African blood tonic (Eremomastax speciosa) and African padauk (Pterocarpus soyaxuii) leaves after simulated in vitro digestion. The results of the phytochemical screening, Eremomastax speciosa (African blood tonic) revealed the presence of tanins, steroids, flavonoids, terpenoids and cardiac glycosides while Pterocarpus soyaxuii (African padauk) revealed the presence of alkaloid, terpernes, flavonoids and cardiac glycosides. The non-enzymatic antioxidant assays of the African blood tonic and African Padauk leaves showed that the digested samples have low antioxidant capacity when compared to organic solvent extract in most of the assays. However, results of the endogenous antioxidant assay showed that both digested and undigested samples of the vegetal matter possess appreciable level of endogenous enzyme upregulation potential, which are not significantly different. The research has also been able to provide information on the antidiabetic potential of the digested and undigested samples of both plants. Digested samples of both African blood tonic and African Padauk leaves showed better and appreciable antidiabetic properties (α-amylase, α-glucosidase, non-enzymatic glycosylation of hemoglobin, glucose uptake rate by yeast cell, glucose diffusion inhibitory assay) when compared to the undigested samples. The bioactive compounds in the digested samples of both study plants are more than the undigested samples. In silico studies on the bioactive compounds gotten from the samples revealed that 11 bioactive compounds from the digested and undigested samples of both study plants have high binding affinity and hence high docking score when compared with acarbose (standard drug) against α-amylase and α-glucosidase which are the key enzymes implicated in Type 2 diabetes. Conclusively, the non-enzymatic antioxidant assays of the African blood tonic and African Padauk leaves showed that the digested samples have low antioxidant capacity when compared to organic solvent extract in most of the assays. Whereas, the results of the endogenous antioxidant assay showed that both digested and undigested samples of the medicinal plants possess very appreciable level of endogenous enzyme upregulation potential. The digested samples of both African blood tonic and African Padauk leaves showed better and appreciable antidiabetic properties when compared to the undigested samples. Therefore, the studied plant can be harnessed as antioxidant bio-resource and antidiabetic agent after passing through the gastro-intestinal tract