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Yams (Dioscorea species) and cocoyam (ariods) are major staples that are widely consumed in tropical and subtropical countries, especially Nigeria.Up till now, there is limited information on the phenolic compounds and antioxidant activity of yams and cocoyam species in this tropical region.Three under-utilized Nigerian yams (Dioscoreacayenensis, Dioscoreadumetorum, Dioscoreabulbifera) and cocoyam (Xanthosomamaffa (Scoth)) were analyzed for total polyphenols, total flavonoids and antioxidant activities applying three commonly used assays: DPPH, ABTS, and ORAC. Correlation analysis wasperformed to determine the contribution of polyphenols and flavonoids toantioxidant activities. The total polyphenol content of the samples ranged from 7.02 to 163.37mg Gallic Acid Equivalent(GAE/100gFW), while the total flavonoid content of the samples ranged from 3.14 to 155.38mg Catechin Equivalent(CE/100gFW). The antioxidant activities evaluated by DPPHassay ranged from 88.17 to 729.39 Trolox Equivalent (TE/100gFW), whileABTSvalues ranged from 32.49 to 756.0 Trolox Equivalent (TE/100gFW)and ORAC assay ranged from 459.29 to 669.45mg Trolox Equivalent (TE/100gFW) respectively. Significant correlation was observed between total polyphenols and DPPH radical scavenging activity (R 2 =0.897);total polyphenols and ABTS(R 2 =0.931),andbetween total polyphenols and ORAC (R 2 =0.707). The correlation between total flavonoid and DPPH(R 2 =0.992), and between total flavonoidand ABTS(R 2 =0.744) respectively. The polyphenol, flavonoid and antioxidant activity of Xanthosomamaffa (Scoth) were higher and significantly different (P<0.05) from the yamsDioscoreaspecies. Extracts from these under-utilized yams and cocoyam tubers can play a considerable role in boosting immunity against human diseases caused by free radical reactions like cancer, cardiovascular disease, diabetes and aging.

This study evaluated the phytochemical and nutrient composition of four selected vegetables consumed in Nigeria, namely, bush mallow (ahihara), garden egg leaf (okpokwa),African spinach(inine), and bush okro (ewedu). They were analyzed for proximate, minerals, vitamins and phytochemical contents. Proximate values maintained the following ranges: moisture 6.73% to 91.22%, protein 7.05% to 32.12%, crude fiber 2.75% to 6.36%, ether extract 3.15% to 6.81%, ash content 2.81% to 6.81% and carbohydrate 48.75% to 72.62% while energy value ranged from 340.54kcal to 363.07kcal. The vitamin contents for these vegetables ranged as follows: vitamin A 0.13.mg/100g to 370.64mg/100g, thiamin (vit B1) 3.12mg/100g to 7.45mg/100g, riboflavin (vit B2) 0.08mg/100g to 3.96mg/100g, vitamin B3(niacin) 0.17mg/100g to 1.91mg/100g, and vitamin C 39.84mg/100g to 98.75mg/100g. The mineral content, namely, calcium ranged from 45.61mg/100g to 430.69mg/100g, magnesium 11.05mg/100g to 198.14mg/100g, potassium 49.82mg/100g to 708.28mg/100g, sodium 2.36mg/100g to 22.98mg/100g. Also the phytochemical contents of the vegetables for phytate ranged from 0.47% to 3.04%, tannin 0.10% to 1.01%, saponin 0.16% to 2.56% and oxalate 0.63% to 0.72%. The results obtained from these vegetables show that they can contribute qualitatively to the nutritional need of the Nigerian population especially among the rural dwellers where vegetables is major food source.

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