Nutritional and Bioactive Potentials of an Underutilized Vegetable— Vitex doniana

The use of lesser-known plant foods in addressing nutritional deficiencies is gaining popularity particularly in developing countries where malnutrition is endemic. This study investigated the proximate, minerals, vitamins, amino acids, tannins, phenolic acids, alkaloids, caratenoids, phytosterols and glycosides composition of the leaves of Vitex doniana using AOAC and gaschro-matographic methods. The leaves had high (g/100g) fiber (14.67 - 35.39) and protein (15.46 - 37.30); but poor in lipid (0.80 - 1.93) and carbohydrates (4.02 - 9.70) corresponding to 58.68% - 141.56%, 30.92% - 74.60%, 1.23% - 2.97% and 1.34% - 3.23% daily value. The protein had relatively high level of essential amino acids (40.94). The leaves were rich in vitamins A, C and E; mineral elements, iron, copper, manganese and cobalt. Tannic acid constituted 100% of the tannins; ferulic acid (46.99%) for phenolic compounds; viticin (99.96%) of total alkaloids; lutein (35.62%) for carotenoids; vanillic acid (49.78%) and sitosterol (61.6%) for phytosterols while the most abundant of the glycocides was agnuside (72.64%) in the leaves. This result indicated that Vitex doniana leaves are a good source of nutrients and bioactive compounds for better nutrition and general wellbeing.


Introduction
In many African countries the fight against malnutrition and under-nourishment continues to be a basic goal of development and variety of strategies is being applied. Strategies based on nutrient-rich foods like vegetables are considered es-

Determination of Percent Daily Value
By comparing to daily values [11], per cent daily values were calculated, as follows: and 241.32 kPa. The oven was programmed initially at 110˚C, ramped at 7˚C/min to 320˚C; and kept at 320˚C for 5 min.

Evaluating Digestible Indispensable Aminoacid (DIAA) Reference
Ratio and DIAA Score The digestible indispensable aminoacid (DIAA) (IAA) in the test proteins were determined by comparing their aminoacid composition, with WHO reference protein patterns [13], according to the following equation: The DIAA with the least DIAA reference ratio became the limiting amino acid while its ratio was converted to percentage to get the digestible IAA score (DIAAS) (13).

Results and Discussion
The daily values per 100g of the leaves ( The results of the amino acid composition and DIAA reference ratios of the leaf protein are presented in Table 2 and Table 3 respectively. They are rich in essential amino acids, 40.94% except for tryptophan that was not detected and can meet the daily requirements [11] for essential amino acids except for lysine. In comparison to the WHO reference protein pattern for infant (birth to 6 months), child (6 months to 3 years) and older child, adolescent, adult [13], the DIAA ratio of the leaf protein were the least, 2.45, 3.00 and 3.50 respectively for methionine though tryptophan was not detected. However, the leaf protein can be used for the supplementation of all the detected essential amino acids except lycine and methionine in all the groups. Every 100 g of the leaf protein contains 32.5 g essential amino acids, 4.5 g sulphur containing amino acids and 7.7 g of aromatic amino acids ( Table 2).
The vitamin composition of Vitex doniana leaves is presented in Table 4.
Ten mineral elements, (five macro and five trace elements) were detected. The leaf is a good source of the trace elements iron, copper and manganese. This report is supported by [24]. They have higher percent daily values than the other detected mineral elements. The high iron and copper content of the leaves suggests that the two mineral elements will be well metabolized from the leaf because of the synergistic relationship between the two trace elements. The metabolic fates of copper and iron are intimately related. Systemic copper deficiency generates cellular iron deficiency, which in humans results in diminished work lasmin, an iron-oxidizing enzyme in blood [27]. The observation of anaemia in copper deficiency may probably be related to its role in facilitating iron absorption and in the incorporation of iron into haemoglobin [28].
The result indicated that Vitex doniana leaves had low sodium/potassium ratio (0.047) and relatively high calcium/phosphorus ratio (1.43). Sodium/potassium ratio is associated with blood pressure (BP) in humans [29] [30] [31] [32]. High sodium and potassium intake are known to be related to high and low blood pressure, respectively [33] [34] [35]. High calcium/phosphorus ratio is vital to bone health and development particularly for infants [36]. The tannins, alkaloids and phenolic acids composition are presented in Table   6. Only tannic acid 0.1590 -0.3440 mg/100g was identified in the Vitex doniana leaves. The concentration was slightly lower in fluted pumkin [37]) and slightly higher in Venonia sp [38]). Tannic acid or tannin is a bitter tasting substance.
The leaf probable owes its strong bitter taste to this compound. It also acts as an astringent when consumed or applied topically, which means it shrinks or constricts the body tissues which may be the reason why the leaf is used for treating wound [39]). It is also believed that the tannin in the leaves is the reason for its use by rural dwellers in traditional medicine for treatment of anaemia with huge success [40] [41] and also its haemopoetic properties [42] [43]. Food and Nutrition Sciences Viticin is reported to have lactopoietic properties [45]. It aids in initiating, maintaining, and augmenting of adequate milk production. Dopamine is a neu-rotransmitter that plays several important roles in the brain and body like impact mood regulation, muscle movement, sleep patterns, ability to store and recall memories, concentration, appetite, and ability to express self-control. Tryptamine is an indolamine metabolite of the essential amino acid, tryptophan. In the human gut, symbiotic bacteria convert dietary tryptophan to tryptamine, which activates 5-HT 4 receptors and regulates gastrointestinal motility. [46] [47] [48]. Tryptamine has been shown to activate trace anime-associated receptors expressed in the mammalian brain, and regulates the activity of dopaminergic, serotonergic and glutamatergic systems [49] [50].
Vanillic acid and ferulic acid had the greater percentage of the detected phenolic acids, 49.78% and 46.99% respectively. Vanillic acid has been shown to be protective against cardiac toxicity caused by oxidative stress [51]. Ferulic acid has been reported to have many physiological functions, including antioxidant, antimicrobial, anti-inflammatory, anti-thrombosis, and anti-cancer activities. It also protects against coronary disease, lowers cholesterol and increases sperm viability [52]. Many studies have shown a strong and positive correlation (p ≤ 0.05) between the phenolic compound contents and the antioxidant potential of fruits and vegetables [53] [54] [55]. This antioxidant mechanism, present in the plants, has an important role in the reduction of lipid oxidation in (plant and animal) tissues, because when incorporated in the human diet, not only it conserves the quality of the food, but it also reduces the risk of developing some diseases [56] [57].

Conclusion
The study has shown that Vitex doniana leaves have high nutritional potentials as well as possess some bioactive compounds. Consequently, if the vegetable is consumed in sufficient amount it may help in combating diseases associated with malnutrition as well as maintaining the overall wellbeing. Therefore, Vitex doniana plant, deserves protection in the wild and its domestication should be promoted.