Evaluation of the Phytochemical Content of Some Edible Grains Marketed in Nigeria

Food grains represent the main supplementary energy source in starchy food-based diets consumed by large segments of people living in Nigeria and many other developing countries. Grains such as millet, wheat, guinea corn etc constitute staple diets of most of the people living in Northern Nigeria while in other parts of the country they are eaten as complement foods. Generally grains have found good applications in food products and animal feeds. They are good sources of metabolizable energy, dietary minerals, proteins, carbohydrate and vitamins.


Introduction
Food grains represent the main supplementary energy source in starchy food-based diets consumed by large segments of people living in Nigeria and many other developing countries.Grains such as millet, wheat, guinea corn etc constitute staple diets of most of the people living in Northern Nigeria while in other parts of the country they are eaten as complement foods.Generally grains have found good applications in food products and animal feeds.They are good sources of metabolizable energy, dietary minerals, proteins, carbohydrate and vitamins.
Food grain legumes e.g.beans, lentils, groundnuts, breadfruit, etc. have high nutrient bioavailability, particularly high protein, which allows them to serve as excellent protein supplements to cereal grains 1 .According to Philips and McWaters 2 cereals and food legumes provide a great part of dietary nutrients for large populations of people living in developing countries where protein-rich foods are expensive.
In addition to their nutritionally useful constituents, grains have been found to contain phytochemicals and anti-nutritional factors, which constitute a great health hazard.Thus the nutritional value of food grains can be divided into positive factors, which are nutritionally beneficial and the negative factors, which are non-beneficial.Ahmed et al 3 ., have identified the positive factors as high protein and fibre while the negative factors include anti-nutritional constituents like polyphenols, tannin, phytate, enzyme (Trypsin) inhibitors etc.
According to Aletor and Adeogun 4 , the presence of inherent anti-nutritional components in plants is a major factor affecting the nutritional value of foods and feeds.The objective of this study was therefore to estimate the phytochemical constituents and anti-nutritional factors present in selected food grains from markets in the Niger Delta region of Nigeria.

Experimental
The millet, wheat, Guinea corn, groundnut and breadfruit used in this study were randomly purchased directly from major markets in Abia, Akwa Ibom, Bayelsa, Cross River, Delta, Edo, Imo, Rivers and Ondo States of Nigeria.The grain samples were sorted to remove foreign materials, washed, dried and ground into uniform powder using Author Thomas machine and stored in labeled air-tight bottles till required for analysis.

Phytochemical analyses
Alkaloid contents of the samples were estimated by the alkaline precipitation method described by Harborne 5 .Total phytate contents of the samples were determined using the spectrophotometric method described by Hang and Lantzsch 6 while saponins were quantified according to the method described Obadoni and Ochuko 7 .Flavonoids were determined following the method of Bohm and Kocipai-Abyazan 8 .Total phenols were determined according to the Prucian Blue spectrophotometic method described by Price and Butler 9 while tannins were estimated using the Folin-Dennis spectrophotometric method described by Pearson 10 .

Statistical analysis
Three replicate samples of each food grain from each of the states in the study area were analyzed and values were averaged.Data were assessed by analysis of variance (ANOVA) and Duncan's multiple range tests with a probability p ≤ 0.05.

Results and Discussion
The phytochemicals determined in the food items investigated are presented in Tables 1-6.The range of concentration of alkaloids obtained were groundnut, 1.12-1.36%,millet, 0.50 -0.78%, wheat, 0.52-0.68%, guinea corn, 0.65-0.83%and breadfruit, 0.66-0.92%(Table 1).The highest alkaloid content of 1.36% was obtained from groundnut from Abia State while the lowest concentration of 0.50% was recorded for millet from Cross River State.Groundnut had the highest concentration of alkaloids with a mean value of 1.24±0.08%while wheat had the lowest concentration with a mean value of 0.61±0.06%.Groundnut samples from all the states showed significant differences in their alkaloid contents at p<0.05 while the other food commodities showed some similarities in the alkaloid contents of samples from 2 or 3 states.For instance there was no significant difference between the concentrations of alkaloids in breadfruit samples from Akwa Ibom, Cross River and Rivers States.Alkaloids affect a lot of metabolic activities in the body and most of them possess dramatic physiological activities hence they are widely used in medicine 5 .Alkaloids are toxic to man.Certain plant alkaloids cause serious intoxications in animals and humans and are often mutagenic 3,4 .The concentrations of flavonoids from the samples examined are presented in Table 2. Mean concentrations of 0.82±0.13%,1.56±0.15%,1.78±0.12%,1.48-±0.09%and 2.27±0.55%.In addition, the possible anti tumor action of certain flavonoids has also generated interest [12][13][14] .Perhaps the grains may provide the necessary dietary bioflavonoids required to prevent cancer and the growth of certain tumor in humans when adequate quantities are consumed regularly.Flavonoids have been reported to possess certain biological properties such as antibacterial, antitoxic and anti-inflammatory activities and often function as strong antioxidants, free radical scavengers and metal chelators 15,16 .
The saponins contents of the samples are presented in Table 3.The phytochemical score of the samples showed that saponins ranked last.The mean concentrations of saponins obtained were 0.04±0.02%,0.03±0.02%,0.05±0.03%,0.03±0.02%and 0.05±0.03%for groundnut, millet, wheat, guinea corn and breadfruit, respectively.The highest saponins content of 0.11% was recorded for wheat from Ondo State and the lowest concentration of 0.01% was obtained from groundnut (Ondo State) and guinea corn (Abia and Edo States).From the results obtained, breadfruit and wheat had the highest overall mean saponin compared to the other food items studied.Plant saponins are components of glycosides and are often referred to as "natural detergents" because of their foamy nature.They are known to have both beneficial and deleterious properties depending on their concentration.Saponins have been reported to possess anticarcinogenic properties, immune modulation activities and regulation of cell proliferation as well as health benefits such as inhibition of the growth of cancer cells and cholesterol lowering activity 16 .
b ±0.08 Values are mean ±S.D of three determinations.Values not sharing common superscript letter (s) in a column are significantly different at P<0.05.

Table 2 .
Flavonoid content of grains, (%).The highest flavonoid content of 3.16% was obtained from breadfruit from Abia State while the lowest concentration of 0.65% was recorded for groundnut from Abia State.Breadfruit had the highest flavonoid content (overall mean = 2.27±0.55)compared to the other food items studied.Plant Flavonoids have attracted attention as potentially important dietary cancer chemoprotective agents a ±0.55 Values are mean ±S.D of three determinations.Values not sharing common superscript letter (s) in a column are significantly different at P<0.05.
Values are mean ± S.D of three determinations.Values not sharing common superscript letter (s) in a column are significantly different at P<0.05.