ABSTRACT

Extraction, characterization and evaluation of bioactive constituents of eight indigenous legumes variously processed namely African breadfruit (Treculia africana) seeds, bambaranut (Vigna subterranean L.), red bean (Phaseolus vulgaris), pigeon pea (Cajanus cajan), cowpea (Vigna unguiculata L.), African yam bean (Sphenostylis stenocarpa) seed, African oil bean (Pentaclethra mycrophylla Benth.) seed and groundnut (Arachis hypogea L.) were studied using standard methods. The results of the chemical composition showed that legume samples vary significantly (p< 0.05) in all the parameters evaluated. Groundnut, African oil bean seed and African breadfruit had significantly higher protein, carbohydrate, fat and ash contents compared with other legumes. Also, groundnut, African oil bean and African breadfruit showed superiority in mineral and fibre abundance while, bambaranut had the lowest mineral and fibre contents. Linolenic acid is the most abundant fatty acids with values ranging from 38.78 – 84.57%. Percentage PUFA ranged from 40.15 – 48.97%. The total essential amino acids ranged from 24.11 – 66.67 mg/100 g. Extraction variables significantly (p<0.05) influenced the total phenolic yield of all the samples. Acetone extraction solvent gave the highest yield of total phenolic compounds in African breadfruit, African oil bean, African yam bean seed and groundnut; while ethanol extraction solvent gave the highest yield in bambaranut and cowpea; and methanol extraction solvent in red bean and pigeonpea. Processing methods applied significantly (p<0.05) influenced the total phenolic, tannin, anthocyanin, carotenoid and flavonoid contents of the samples. Pressure cooking exhibited a significant (p<0.05) reduction in the phenolic, tannin, anthocyanin, carotenoid and flavonoid contents in all the samples with increasing cooking time, however, there was minimal increase in the total phenolic and carotenoid contents of red bean, total anthocyanin of red bean and African oil bean. Roasting temperatures significantly (p<0.05) reduced the phenolic content of the samples except in bambaranut, red bean and African oil bean where there were increases with increasing cooking time. The tannin, anthocyanin, carotenoid and flavonoid contents were significantly (p<0.05) reduced with increasing roasting temperatures. Fermentation reduced the phenolic, tannin, anthocyanin, carotenoid and flavonoid contents of the samples with increasing fermentation time. However, red bean showed minimal increase with increasing fermentation time. There was significant (p<0.05) increase in the total phenolic content of all the samples with increasing germination time. But, tannin and flavonoid showed significant (p<0.05) reduction with increasing germination time. Germination significantly (p<0.05) reduced the carotenoid and anthocyanin levels in all the samples, however, red bean, pigeonpea and African oil bean showed increases with increasing germination time. Samples evaluated exhibited significantly (p<0.05) different antioxidant capacities. African oil bean and groundnut had the highest antioxidant activities 52.18% and 52.16%, respectively while, African yam bean seed was the lowest (19.85%). Similar trend was observed in the reducing power of the raw samples where groundnut, bambaranut and African breadfruit showed significantly (p<0.05) higher reducing power. Three (3) days germination significantly (p<0.05) increased the antioxidant capacities by 14.65%, 18.42%, 53.58%, 52.84%, 17.24%, 14.56%, 53.18% and 43.03% in African oil bean, bambaranut, cowpea, red bean, African breadfruit, groundnut, African oil bean and  pigeonpea, respectively. The GC-MS analysis revealed the presence of diverse bioactive compounds which exhibit antitumor properties, antimicrobial properties, antidepressant, enzymes inhibition, bio stimulation, restoration of regular heartbeat.