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 . This remains a serious problem in Africa where the population was above exceeded 1 billion in 2009 and continues to grow . 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  . Most of the plant species can provide food and are used to complete nutrients . Otherwise, they are used for traditional medicines , such as Dioscorea rotundata , Maerua pseudopetalosa  and Cyperus esculentus . 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 . Recently, the therapeutic properties of N. lotus’s leaves have been demonstrated in the treatment of breast cancer , in the regulation of blood pressure and the restoration of erectile function . Rhizomes of Nymphaea are also used for tanning . 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 , in Equateur Province-R. . 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 . They have numerous socio economic uses in the region of Senegal River valley  such as ornamental characters , sold for therapeutic properties  , and for tanning . 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.
2. Material and Methods
2.1. Biological Materials
Three batches of water lily seed were established from three species. N. lotus with black seeds (batch 1); N. lotus with red seeds (batch 2) and N. micrantha (red seeds (Figure 1). Each N. lotus batch consist of 3 samples collected from three effluents of the Senegal River at the villages of Ndiaye (16˚12'7"W; 16˚15'55"N), Mboudom (16˚03'30"W; 16˚25'45"N) and Ndiandane (14˚59'12"W;
Figure 1. A = N. lotus’ with Black seeds; B = N. lotus with Red seeds; C = N. micrantha with red Seeds.
16˚35'06"N). The third batch of N. micrantha seeds (Lot 3) is made of two samples from two effluents in Saint-Louis (16˚24'21"W; 16˚03'24"N) and Ross-bethio (16˚07'05"W; 16˚17'59"N). The samples are dried in the shade at room temperature (30˚C) for 48 hours and sent to the laboratory for characterization.
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  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 . 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 . The lipid determination was carried out by weighing the fats after Soxhlet extraction with diethyl ether according to the method NF V 03-905 . 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 .
2.3. 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.
3. 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) . 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 . Water lily seeds are also consumed in northern Ghana , Equator Province of Congo , China, East India and the Philippine Islands . 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) , 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.
3.1. 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 . 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  . 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% . However, they are higher than those of N. lotus seeds reported in Nigeria by Mohammed et al., 2013  (4.18 ± 0.176) and Wasagu et al., 2015  (6.00% ± 0.45%). This difference could be
Table 1. Proximate components and energy value of Nymphaea’s seeds.
DM: dry matter; a, b, c: In the same row, means followed by a different letter are significantly different at the P < 5% threshold (Newman and Keuls’ method).
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 . Several previous works highlight the importance of moisture as it has an impact on processing conditions and product stability .
3.2. Proximate Components
The protein content (Table 1) is between 7.90% ± 1.25% and 8.24% ± 0.5% DM. The results have showed that N. micrantha seeds and N. lotus seeds have significantly identical protein contents (P-value > 0.05). The highest level was observed in black N. lotus seeds (8.24 ± 0.5). The protein level obtained in the seeds of Nymphaea. spp (above 7.5%) is close to the values of Vigna unguiculata variety Katiola (10.193 ± 0.075) . However, they are much higher than the values reported by Musa et al. (2012)  (3.09% ± 0.08%) and Wasagu et al. (2015)  (1.04% ± 0.17%) for N. lotus seeds.
The determination of the lipid level allows the evaluation of the energy reserve of Nymphaea seeds. The range varies from 2.32% ± 0.45% to 4.29% ± 1.0% with a highest content in black N. lotus seeds (4.29% ± 1.0%) and lowest in red N. lotus seeds (2.32 ± 0.45). N. micrantha had a content of 2.71% ± 0.5%. Lipid contents did not vary according to the types of seeds analysed. However, they are comparable to those reported for Pennisetum glaucum (6.0 ± 1.5) , Zea mays (6.1 ± 2.3), Sorghum bicolor (4.5 ± 0.9), Digitaria exilis (3.25% ± 3.9)  and Cicer arietinum (6.0 g/100) . However, they are higher than those of pulses such as Pisum sativum (1.2 g/100), Phaseolus vulgaris (0.9 g/100) and Lens culinaris (1.1 g/100) .
Carbohydrate levels in Nymphaea sp. seeds range from 74.49% ± 0.9% to 77.66% ± 1.65% DM (Table 1). No significant differences were observed following a statistical comparison of the means. The species N. micrantha had the highest seed content (77.66% ± 1.65% DM) while the black and red seeds of N. lotus contain less with 76.04% ± 1.36% and 74.49% ± 0.9% respectively. Stored in the form of starch in cereals, carbohydrates are assimilated to natural laxatives which can facilitate digestion and thus constitute a source of energy used in a primordial way by the organism . Moreover, the carbohydrate contents found in this study are similar to those reported by Wasagu et al. (2015)  in leaves (71.83% ± 1.63%), roots (61.31% ± 1.86%) and seeds of N. lotus (80.96 ± 0.37). They are also comparable to those of Sorghum bicolor (74.4 ± 2.0)  and Digitaria exilis (79.05% ± 23.9%) . This high quantity in Nymphaea seeds could be an asset for their valorization in the manufacture of marketable by-products such as starch, glucose and even alcohol.
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 reported by Musa et al., 2012  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.
3.3. 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 Table 3. The results for sodium showed no significant difference (P > 0.05) between the three types of seeds and are low (11.0 mg/100g in average). However, for potassium, calcium and magnesium, there was a significant difference between N. micrantha seeds and red and black N. lotus seeds. N. micrantha seeds are the ones containing more minerals with 770.81 ± 42.33 for potassium, 518.67 ± 15.23 for magnesium, 296.52 ± 16.3 for calcium and 13.52 ± 1.14 mg/100g for sodium. Moreover, the three types of seeds analysed showed a higher potassium content (ranging from 454 to 770.81 mg/100g), similar to berries and exotic fruits (e.g. strawberry, blackcurrant, grape, African akee, orange, avocado, banana, date, fig) which
Table 2. Comparison between Nymphaea seeds analysed in this study and others seeds reported .
Table 3. Mineral content of Nymphaea’s seeds.
contain 59 to 782 mg/100g dry matter . However, the sodium content is found to be the lowest among the dosed minerals. This remark is confirmed by Musa et al., 2012 . 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  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.
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.
The publication fee of this paper was possible thanks to the support of the European DAfrAli research project.
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