Nymphaea lotus L. and Nymphaea micrantha Guill. et Perr Seeds as Cereal Substitute in the Delta of Senegal River

Studies conducted in the delta and lower valley of Senegal river have demonstrated through ethnobotanical surveys, the importance of Nymphaea lotus L. and Nymphaea micrantha Guill. et Perr in the diet and in the pharmacopoeia. The seeds are used with good appreciation by the indigenous population as a welding food. But studies addressing their biochemical and nutritional aspects are still very rare in the literature. This study was initiated in order to fill this gap and allow a better appreciation of the nutritional and energetic potentialities of these seeds. For this purpose, seeds were collected in effluent from the Senegal River, dried in the shade and put into three different batches: a batch of red seeds of N. lotus, a batch of Black seeds of N. lotus and a batch of seeds of N. micrantha. The biochemical analyses gave their moisture content (9.17% ± 0.2% to 13.36% ± 3.46%), aw (0.46% to 0.71%), protein (7.90% ± 1.25% to 8.24% ± 0.5%), lipid (2.32% ± 0.45% to 4.29% ± 1.0%), carbohydrate (74.49% ± 0.9% and 77.66% ± 1.65%), mineral matter (1.77% ± 0.06% to 2.55% ± 0.08%). All three types of seeds have high levels of potassium (481.10% ± 17.62% to 770.81% ± 42.33%), magnesium (312.71% ± 14.08% to 518.67% ± 15.23%) and calcium (188.81% ± 8.52% to 296.52% ± 16%. Their energy values (350.54 ± 15.21 kcal/100g to 375.7 ± 3.48 Kcal/100g), are closed to other cereals consumed in the human diet in Senegal. Therefore, these seeds offer the opportunity to diversify the diet in the delta and lower valley of the Senegal River.

poeia. The seeds are used with good appreciation by the indigenous population as a welding food. But studies addressing their biochemical and nutritional aspects are still very rare in the literature. This study was initiated in order to fill this gap and allow a better appreciation of the nutritional and energetic potentialities of these seeds. For this purpose, seeds were collected in effluent from the Senegal River, dried in the shade and put into three different batches: a batch of red seeds of N. lotus, a batch of Black seeds of N. lotus and a batch of seeds of N. micrantha. The biochemical analyses gave their moisture content (9.17% ± 0.2% to 13.36% ± 3.46%), aw (0.46% to 0.71%), protein (7.90% ± 1.25% to 8.24% ± 0.5%), lipid (2.32% ± 0.45% to 4.29% ± 1.0%), carbohydrate (74.49% ± 0.9% and 77.66% ± 1.65%), mineral matter (1.77% ± 0.06% to 2.55% ± 0.08%). All three types of seeds have high levels of potassium (481.10% ± 17.62% to 770.81% ± 42.33%), magnesium (312.71% ± 14.08% to 518.67% ± 15.23%) and calcium (188.81% ± 8.52% to 296.52% ± 16%. Their energy values (350.54 ± 15.21 kcal/100g to 375.7 ± 3.48 Kcal/100g), are closed to other cereals consumed in the human diet in Senegal. Therefore, these seeds offer the opportunity to diversify the diet in the delta and lower valley of the Senegal River.

Introduction
Food security and safety are major challenges in countries around the world, currently facing climate hazards and population growth. All over the word, 821 million people or one person out of nine, are suffering from hunger in 2017 [1]. This remains a serious problem in Africa where the population was above exceeded 1 billion in 2009 and continues to grow [2]. However facing to these challenges there is growing interest to consider the called neglected and under-used species. In fact, they have considerable potential to ensure food security and cover the population's health, care needs and contribute to the poverty reduction effort [3] [4]. Most of the plant species can provide food and are used to complete nutrients [5]. Otherwise, they are used for traditional medicines [6], such as Dioscorea rotundata [7], Maerua pseudopetalosa [8] and Cyperus esculentus [9]. Wild fruits of Nymphaea lotus and Nymphaea micrantha also fall into this group. They are aquatic species that are abundant in the freshwater of the Senegal River valley. Attention has so far focused on their ornamental character through their domestication [10]. Recently, the therapeutic properties of N. lotus's leaves have been demonstrated in the treatment of breast cancer [11], in the regulation of blood pressure and the restoration of erectile function [12]. Rhizomes of Nymphaea are also used for tanning [13]. In terms of food, almost all part of the species are useful (leaves, peduncles, flowers, stems, rhizomes and seeds) of the genus Nymphaea are edible such as in Northern Ghana [14], in Equateur Province-R. [15]. All these studies have shown the potential that can still be derived from these species. In Senegal, seeds of N. lotus and N. micrantha have been used to supplement diet in time of food shortage [16]. They have numerous socio economic uses in the region of Senegal River valley [16] such as ornamental characters [10], sold for therapeutic properties [11] [12], and for tanning [13]. Despite the importance of those species there is a dearth of information on their biochemical and nutritional components. This study was initiated in order to fill this gap and to allow a better appreciation of the nutritional potentialities of Nymphaea's seeds.

Methods
Caracterization of Nympea's seeds consist to determine several parameters. The moisture content of the seeds was determined after dehydration at 105˚C according to the official method AFNOR NF V 03-921. The nitrogen component was determined by Kjeldhal's method according to NF 03-050 [17] and proteins were calculated using 5.7 as coefficient. The total minerals were determined after 4 hours incineration at 550 ˚C according to V76-101 method [17]. After incineration the ashes were collected in a mixture of hydrochloric and nitric acids. The content of potassium, calcium, magnesium and sodium were evaluated by determination with an atomic absorption spectrometer according to the guidelines of the AFNOR standard NF V76-122 [17]. The lipid determination was carried out by weighing the fats after Soxhlet extraction with diethyl ether according to the method NF V 03-905 [17]. The carbohydrate content was evaluated by calculation, using the average between the content of water, ash and other organic matter of (protein or nitrogen component and lipid content). The energy value is calculated according to Atwater formula [18].

Statistical Analyzes
The one-way analysis of variance (ANOVA) test was used in this research combined with the STATISTICA 7.1 software at 5% level of significance. Through this statistical analysis samples are compared according to each parameter. Statistical differences with a probability value less than 0.05 (P < 0.05) are considered significant.

Results and Discussion
This study has determined the major biochemical composition of N. lotus and N. micrantha seeds and assessed their energy and nutritional intake. This preliminary work is one of nutritional interest following previous studies in the same region by Gueye et al. (2019) [16]. These two species are prized and edible in the delta and lower Senegal River's valley. Their fruits are globular and filled with seeds. They can undergo stages of sun drying and grinding into flour that is often consumed in main dishes [16]. Water lily seeds are also consumed in northern Ghana [14], Equator Province of Congo [15], China, East India and the Philippine Islands [10]. Floury bulbs reminiscent of potatoes; they are roasted, boiled or cooked under ashes and can be dried and reduced to flour, According to Betti and Mebere Yemefa (2011) [19], in the far north of Cameroon, the flowers and stems are also consumed as appetizers. All these uses showed that species of this genus are potentially valuable for human consumption.

Moisture and Water Activity
Water activity values varied between 0.46% and 0.71% and the lowest is noted in N. lotus black seeds (Table 1). Water activity has values below 0.75% and is in the considered in food chemistry to stabilize food [20]. Table 1 shows a significant difference with respect to the water activity (Aw) from different seeds analysed (P-value < 0.05). Water activity is an important parameter in food that can prevent the risk to spoil the food. The biochemical and microbiological stability of food could be compromised if the values are too high, as this would reduce the shelf life [21] [22]. In general, N. lotus and N. micrantha seeds have Aw's values that guarantee their good stability. The low values are correlated with those of the water content. To characterize the samples, the moisture content is generally low (not exceeding 10%), indicating good seed storage. Moisture values obtained is between 9.17% ± 0.2% and 13.36% ± 3.46% (Table 1). Comparison of the averages shows that the moisture contents are statistically identical (at the 0.05 threshold) between the three types of seeds. Nevertheless, red N. lotus seeds have higher moisture contents than black seeds (13.36% ± 3.46% and 9.66% ± 0.61% respectively). These values are close to those of peanuts, beans, and pigeon peas, which average 10% [23]. However, they are higher than those of N. lotus seeds reported in Nigeria by Mohammed  due to local thermal and hygrometric conditions. The moisture content from seeds is a determining factor in the prevention of insect infestations as dried grains with a moisture content below 12% inhibit the development of most insect pest species [23]. Several previous works highlight the importance of moisture as it has an impact on processing conditions and product stability [26].
Regarding the energy intake of these seeds in human food, black N. lotus seeds have the best values (375.7 ± 3.48 Kcal/100g). N. micrantha seeds and red N. lotus seeds have significantly different values and respectively 366.65 ± 2.97 kcal/100g and 350.54 ± 15.21 kcal/100g (Table 1). These values are close to those  [28] for N. lotus seeds (399.35 kcal/100g). They are also close to those others species commonly consumed in the human diet (Table   2). This shows that N. lotus and N. micrantha seeds can contribute to dietary diversification and provide a very good source of energy.

The Mineral Matter of Nymphaea Seeds
The total mineral content was 2.55% ± 0.08% for N. micrantha, 1.77% ± 0.06% for black N. lotus seeds and 1.89% ± 11% for red N. lotus seeds, with a significant difference between N. micrantha and red N. lotus seeds ( Table 3). The black N. lotus seeds have a content close to both types of seeds. The major mineral content of the different Nymphaea seeds is presented in   [34]. However, the sodium content is found to be the lowest among the dosed minerals. This remark is confirmed by Musa et al., 2012 [28]. In general, apart from sodium, all other minerals from the three types of seeds (potassium, calcium, magnesium) have high values that are above 180 mg-100 g-1 dry matter. This is an indication that seeds of Nymphaea spp. would probably be important for the prevention of certain diseases. Indeed, these nutrients have a positive impact on the maintenance and regulation of blood pressure [35] which remains one of the biggest problems of our populations.
This study has shown that Nymphaea spp. seeds are seeds are comparable to cereals that are important in the diets of populations all over the word. This justifies their use in the past as a substitute for rice and millet during the dearth period. In addition, Nymphaea spp. seeds offer an opportunity for rural women to improve their income by adding value to them and marketing them on a larger scale.

Conclusion
This study is a contributory approach in the knowledge of neglected and under-used species in order to better understanding of their nutritional input. The dietary importance of N. lotus and N. micrantha seeds was demonstrated to be a good manner to diversify the diet. However, regarding valorization, some complementary investigations such as secondary metabolites, fatty acids profile, should improve a better knowledge of these seeds.