In-vitro Antioxidant Capacity, Phytochemical Characterisation, Toxic and Functional Properties of African Yam Bean (Sphenostylis stenocarpa) Seed-Enriched Cassava (Manihot esculenta) Product (Pupuru)

Abstract

Aims: This study aimed at determining the In-vitro antioxidant capacity, characterise phytochemical constituents, assess toxic and functional properties of African yam bean (Sphenostylis stenocarpa) seed-enriched Cassava product (Pupuru) flour blends using standard methods. Methodology: Pupuru flour blends were produced from spontaneously-fermented cassava tubers substituted with African yam bean (Sphenostylis stenocarpa) seed (AYBS) (5% (EP5), 10% (EP10) and 15% (EP15), before toasting, cooling, milling, sieving and packaging. A commercial sample (CP) with 100% cassava and another produced in this study, were used as controls. Results: In-vitro 2,2-Azino-bis (3-ethylbenthiazoline-6-sulphonic acid) (ABTS) and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging abilities, total flavonoid content (TFC), ferric reducing antioxidant power (FRAP) and total phenol content (TPC) increased significantly (P = .05) as AYBS enrichment levels increased. The commercial and laboratory control samples showed no significant difference (P = .05) in all the antioxidants analysed except DPPH: ABTS (7.61- 12.27%); DPPH (26.34-48.26%); TFC (0.10-0.25 mg CAE/g); FRAP (0.81-2.36 (mg/g) and TPC (15.74- 24.15 mg GAE/g). All the phytochemicals except tannins increased significantly (P = .05) as levels of enrichment with AYBS increased. Tannins, phytates, saponins, alkaloids and oxalates were 1.46 -2.87 (mg/g); 0.85-1.40 mg/100 g; 4.18-13.27 mg/g; 24.89-29.05 mg/g and 1.71-3.23 mg/g, respectively. The toxic constituent revealed that all the samples contained significantly different (P = .05) cyanide ranging from 0.87-2.51 mg/kg which reduced as AYBS level of inclusion increased. The functional properties of the samples were significantly (P = .05) enhanced with AYBS enrichment. Conclusion: Utilisation of AYBS to enrich Pupuru increased its In-vitro antioxidant capacity and phytochemical constituents, reduced the toxic cyanide content enhanced the functional properties, hence, its suitability as a nutraceutical to delay the ageing process and prevent cardiovascular diseases.