Nutritional composition, antioxidant assay and α-glucosidase inhibitory flavonoids from the fruits of Carissa edulis Vahl (Apocynaceae)

Carissa edulis Vahl (Apocynaceae) is a plant whose leaves, roots and fruits are traditionally employed for the treatment of malaria, microbial infections, headache, cough, fever and ulcer among many others. Fresh fruits of Carissa edulis were crushed and extracted with 70 % methanol for 72 hours to obtain MeOH extract. Proximate analysis as well as mineral composition of the fresh fruits were determined. Total phenolic content (TPC), total flavonoids content (TFC) and antioxidant activity (DPPH, FRAP & Ferrous chelating) of the MeOH extract were determined, while the α-glucosidase inhibitory activity of the extract was conducted using bioautographic assay. The structure of compounds isolated were elucidated by 1D NMR spectroscopic analysis and high-resolution mass spectrometric (HRESIMS) data. The results showed that the nutritive value of the fresh Carissa edulis is 43.43 kcal/100 g, while the extract demonstrated good antioxidant activities (DPPH, IC50 = 87.98 μg/ml; FRAP, EC50 = 464.33 μg/ml & Ferrous chelating, EC50 = 294.55 μg/ml). Further study of the MeOH extract of the fruit led to the isolation of rhamnetin-3-β-D-glucopyranoside, peonidin-3-rutinoside and malvidin-3-O-β-D-(6”-acetylglucoside). These results suggest that the fruits of Carissa edulis are nutritious and possess potential antidiabetic effect which corroborated the ethnomedical uses of the fruits. Keywords: Carissa edulis; α-Glucosidase; Anthocyanins; Nutritional composition; Antioxidant properties