NUTRIENTS AND PHYTOCHEMICAL COMPOUNDS OF TWO VARIETIES OF BUSH MANGO (IRVINGIAGABONENSIS) GROWN IN BENIN

Sawab Deen Osseni, Fidèle Paul Tchobo, Andriano Jospin Djossou and Mouaimine Mazou. Unité de Recherche en Génie Enzymatique et Alimentaire, Laboratoire d’Etude et de Recherche en Chimie Appliquée. Ecole Polytechnique d’Abomey-Calavi, Université d’Abomey-Calavi, Bénin, 01 BP 2009. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 2 August 2018 Final Accepted: 4 September 2018 Published: October 2018

In particular, 80% of rural populations in sub-Saharan Africa depends on non-timber forest products (NTFPs) for their health needs (Kalaba et al., 2010). Their biochemical and nutritional contributions (proteins, fats, carbohydrates, minerals and vitamins and fiber (Augustino et al., 2011)) have demonstrated their potential to resolve food, nutrition and health crises in Africa (Okolo et al., 1995;Ahenkan and Boon, 2011;Sossa-Vihotogbé et al., 2012). Irvingia gabonensis (bush mango) is one of NTFPs widespread in the Gulf of Guinea. It is among the species of priority food tree in traditional agroforestry systems and subject to domestication (Franzel et al., 1996). Fruits are economically very important in sub-Saharan Africa for local populations (Asaah et al., 2003, Leakey et al., 2003. In Benin, Irvingia gabonensis is very abundant in the departments of Mono, Couffo and the dense forests of Pobè (Akouêhou, 2012). It is an important source of livelihood and income for many farmers. Indeed, some of these harvested products are intended for self-consumption and another for trade on local, national and regional markets. It is distinguished locally under two varieties («Ewoto» and «Eshito») in the national languages. This distinction has already been mentioned by Okafor (1975) in Nigeria. Thus, the aim of this work was to evaluate the physicochemical characteristics and the antinutritional compounds of the varieties encountered in Benin.

Material and Methods:-Material
Bush mango samples consist of the two varieties identified by indigenous peoples in southern Benin. These are the varieties «Eshito» and «Ewoto». These two varieties were collected in eight township of Benin (Lalo, Tovikilin, Klwehanmè, Aplahoué, Kétou, Pobè, Ifangni, Adja-Ouèrè) and have been stored at 4-6°C before used.
Physicochemical analysis pH and titratable acidity were determined according to the modified procedure of AACC 02-31.01. The pH was measured using a pH meter on a homogenized mixture of 10 g of pulp and 20 ml of distilled water. Titratable acidity is measured on a solution obtained with 10 g of pulp and 90 ml of distilled water. The solution obtained after filtration was titrated with magnetic stirring with sodium hydroxide (0.1 N) to the phenolphthalein end point.
Moisture content of samples was determined by oven methods (ISO 712: 1998). Soluble solids (Brix) was determined using a digital refractometer (ATAGO HSR-500). Protein was analyzed by the Microkjedhal nitrogen method, using a conversion factor of 6.25. Ash was determined according to the standard methods described by the Association of Official Analytical Chemists (AOAC, 1990). The total and reducing sugar contents were measured respectively by the colorimetric method developed by Dubois et al. (1959) and that described by Gonçalves et al. (1900). Ascorbic acid content was determined by dichlorophenolindophenol (Lees, 1975)

Phytochemical analysis
The Folin-Ciocalteu method (Singleton, Orthofer, and Lamuela-Raventos, 1999) was used to determine the phenolic content. The absorbance of the reaction mixture was measured at 760 nm on the spectrophotometer. Oxalates were assayed by the method of Day and Underwood (1986), phytates by the method of Reddy and Love (1999), saponins by the method of Hudson and El Difrawi (1979), flavonoids by the method of Arvouet-Grand et al (1994) and tannins by the method of Trease and Evans (1978).

Results and discussion:
Figures 1 and 2 show the pH, the titratable acidity and the Brix degree of the two varieties of Irvingia gabonesis studied. These results show that the pH of the samples varied from 4.4 to 6.1, for the variety «Ewoto» and from 5.3 to 6.1 for the variety «Eshito». For the titratable acidity, it varied from 0.03 to 0.06 for all varieties. As to Brix degree, it varied from 10.5 to 12 for the «Ewoto» variety and from 10.5 to 15.5 for variety «Eshito».The result shows that the Brix degree and the pH were varied significantly according to the variety and the production area. however, the «Ewoto» variety had the most acidic fruit so it is more stable to deterioration. Indeed, according to Bourgeois (1985), for pH below 4.5, fruit enjoy a microbiological stability and those with pH values close to neutrality would be susceptible to microbial growth. The results of Brix degree show that the variety ««Eshito» » have a significant concentration of soluble matter. These differences may be due to the maturity of the fruits.   Achinewhu (1983). Table 2 presented oxalates, phytates, tannins, saponins and flavonoids content of the samples of Irvingia gabonensis studied. The presence of some of these compounds in fruits gives them well-known medicinal properties. Indeed, flavonoids, saponins and tannins have antimicrobial activity, as well as other physiological activities (Evans 2005). However, they constitute factors of non-absorption or mal-absorption of nutrients in the body.
The results in Table 2 show that the highest values for oxalates, phytates, tannins and saponins were 0.99, 0.91, 0.20 and 6.01%, respectively. These values for total phenols and flavonoids were 0.26 mg GA/100g and 1.06 mg CAT/100g of pulp. The high content of saponides (3.07 -7.47%) were certainly responsible for the bitter aftertaste of the pulp of Irvingia gabonesis. The results do not reveal a significant difference between the values obtained for each parameter. The «Eshito» variety has the highest levels of oxalates, tannins, and flavonoids, while the highest levels of phenolics, phytates, and saponins are obtained from «Ewoto». These results can be explained by the variation of storage duration after harvest. Indeed, according to the work of Etubu (2012), while the content of flavonoids decreases those of saponins and tannins

Conclusion:-
The nutritional contribution of the two varieties of Irvengia gabonensis to the diet of indigenous populations in Benin remains important. These fruits can contribute to the diversification of food in the regions where they are found and constitute a very good source of nutrients for the population. The physico-chemical characteristics studied reveal no significant differences between the two varieties of Irvengia gabonensis. However, further studies will be needed to differentiate them.