Assessment of the Content of β-Carotene, Lycopene and Total Phenolic of 45 Varieties of Tomatoes (Solanum lycopersicum L.)

Tomato is a highly consumed food in the world because of its richness in nutrients especially carotenoids, vitamins and total phenolic. It has been proven very beneficial for the body. This study aimed to evaluate the composition of βcarotene, lycopene and total phenolic of 45 tomatoes varieties from experimental station in Burkina Faso. The content of βcarotene and lycopene was determined by HPLC while the total phenolic contents were analyzed by spectrophotometry. The lycopene content and the β-carotene content of the 45 varieties ranged from 2.41 ± 0.00 (variety 27T4) to 83.51 ± 0.22 (BT1 variety) mg /100 g of dry matter and 0.83 ± 0.00 (variety 27T4) to 26.80 ± 0.08 (Variety BT1) mg / 100 g of dry matter respectively. The total phenolic contents were between 502.84 ± 47.46 (variety 4T1) to 1181.08 ± 182. 97 (variety 25T2) mg GAG /100 g of dry matter. The 45 varieties of tomato analyzed are potential sources of lycopene, β-carotene and total phenolic. Some of the varieties can be promoted for cultivation at national level due to their high content in these three elements.


Introduction
Fruits and vegetables are an excellent source of vitamins and minerals for human body [1]. As part of the daily diet, they prevent major chronic diseases such as heart disease, diabetes, obesity and some cancers [2]. The tomato (Solanum lycopersicum L.) is a very popular and versatile vegetablefruit that is used in the preparation of several dishes. It is a much consumed legume because of its richness in nutrients. Tomato is nutritionally rich in fiber, minerals, vitamins and antioxidants.
The antioxidants are total phenolic compounds, flavonoids, lycopene, vitamin A and vitamin C [3]. By its antioxidant properties, it plays an important role in protecting the body. It is considered to be the primary source of lycopene, which has been shown to reduce the risk of certain chronic diseases [4][5][6][7][8]. Etmina et al., [9] showed that consumption of tomatoes and tomato products prevented prostate cancer. Also, diets that include tomatoes have been associated with the reduction of certain cardiovascular diseases [10]. However, the nutritional composition of tomatoes such as β-carotene, lycopene, and total phenolic may vary depending on variety, Total Phenolic of 45 Varieties of Tomatoes (Solanum lycopersicum L.) climate, maturity and environmental conditions [11][12][13][14][15][16].
Currently, in Burkina Faso, several varieties of tomato are grown, but the most part are varieties imported from other countries. The breeders of these varieties prefer mainly productivity, adaptation to growing conditions and resistance to diseases to the detriment of any other character of interest. The organoleptic and nutritional quality of these varieties on the market no longer satisfies consumers. As a result, the acquisition of good organoleptic and nutritional value has become a major issue. Indeed, the research in Burkina Faso to overcome this problem entailed putting in place varieties whose nutritional composition especially ß-carotene, lycopene and total polyphenols deserve to be known. The objective of this study was to evaluate the β-carotene, lycopene and total phenolic composition of 45 tomato varieties selected by the research station in Burkina Faso (Institute of Environment and Agricultural Research) to see which varieties are potentially nutritional.

Plant Material
Forty-seven (45) tomatoes genotypes were collected from Burkina Faso (27), Mali (12) and Brasilia (6). The details are shown in the table 1. All the genotypes are cultivated at west experimental station of Institute of Environment and Agricultural Research (Bobo Dioulasso) in the raining season from July to October 2015. The experimental design used was RCBD with 4 replications. The cultural practices was followed according Rouamba et al. [17]. To make the samples of biochemical analysis, 1kg of fruit (250g per replication) per genotype was harvested from central plant per plot at the full repining stage and at the thirst harvest. These samples were crushed using a Moulinex type mill in order to obtain a homogeneous paste. These samples were stored in the freezer at -20°C before analyses.

Determination of β-Carotene and Lycopene
Beta-carotene and lycopene were determined by highperformance liquid chromatography (HPLC), method validated by Somé et al. [18]. The analyzes were carried out under yellow light and the sample containers were protected from light by aluminum foil.
Preparations for standard solutions: For each carotenoid (β carotene, lycopene), a small amount (a few milligrams) was dissolved in 3 ml of hexane. Dilutions to 1/10, 1/100, 1/1000 of this solution were carried out. The respective optical densities were measured at 450 nm. The solution with an optical density of between 0.1 and 0.9 was chosen. Its concentration was then calculated according to the formula: DO is the optical density read and e is the molar extinction coefficient.
Preparation of the calibration mixture: From the standard solution thus prepared, the concentration of which was determined, the precise volumes of each solution of carotenoids were taken so as to obtain a solution of final concentration after absorption of 15 pmol in 20 µl for each carotenoid in the mixture. Except for β-carotene, the final concentration of which was 30 pmol / 20 µl. The volumes thus taken were combined, evaporated under nitrogen, and the residue was taken up with 500 µl of acetonitrile to obtain the concentrations indicated above.
Extraction of ß carotene and lycopene: A sample of about 1 g of dough was taken from a tube. The carotenoids were extracted by vortexing with 2 × 2 ml of hexane in the presence of echinenone (internal standard) at a concentration of 0.6 µmol µl -1. After vigorous stirring, the mixture at 3000 rpm-1 for 5 min at -5°C was centrifuged. After centrifugation, the hexane phases were combined and evaporated under nitrogen. The residue thus obtained was taken up in 800 µl of acetonitrile to obtain a solution containing 15 pmol / 20 µl of the internal standard; 20 µl were then injected.
Calculation of the concentration of each type of carotenoid: After injection of the calibration mixture of defined concentration and comprising the internal standard, a relative calibration factor was calculated for each peak: Where f i is the calibration factor of the compound i with respect to the internal standard (SI), A i is the area under the curve or the peak height of the compound i, C i is Concentration of compound i in the mixture. A SI is the area under the curve of the internal standard (SI) and C SI its concentration in the calibration mixture.
The C xi concentration of each carotenoid was given by: Where C xi is the concentration of compound i in the sample and A xi the area obtained after injection of the sample. C SIE and A SIA are respectively the concentration and area under the curve of the internal standard introduced in the sample.

Determination of Total Phenolic
Total phenolic content of the tomato extract was determined by spectrophotometry according to the Folin-Ciocalteu reagent method of Singleton et al. [19] with the modifications.
Extraction: The methanol-HCl 1% solvent was used for extraction. 2.5 g of tomato pulp was placed in a flask and 50 ml of the extraction solvent was added. The vial was protected from light with aluminum foil. The mixture was placed under magnetic stirring for 10 minutes and then in the refrigerator. After 24 hours of maceration, the mixture was filtered with a filter paper N°2. The filtrate was placed in a spherical flask and stored to refrigerator at 4°C until use.
Dosage: An aliquot of 0.250 ml of extract was mixed with 1.25 ml of the Folin-Ciocalteu reagent (0.2 N). After 5 min of incubation at ambient temperature, 1 ml of sodium carbonate solution (75 g / L) was added. The mixture was then placed in a water bath, cooking double boiler, at a temperature of 65°C for 20 min and read at the spectrophotometer at 760 nm against a blank not containing the extract [19]. The measurements were carried out in triplicate. The total polyphenol content was determined from a calibration curve carried out with different concentrations of gallic acid. The results were expressed in mg gallic acid equivalent (GAE) per 100 g dry matter. was stated at P < 0.05.

Lycopene Content (mg / 100g DM)
The  [24]. The variability in lycopene levels between tomato varieties may be due to the varieties themselves but also to the degree of maturity of these varieties of tomato. According to Davies and Hobson [13] Giovanecci et al. [14], Abushita et al. [15] and Thompson et al. [16], the nutritional composition such that the lycopene content may vary depending on the variety and maturity of the tomato.

β-Carotene Content (mg / 100 g DM)
The ß-carotene content of the 45 varieties varied from 0.83 ± 0.00 (variety 14 27T4) to 28.88 ± 0.08 (variety BT1) mg / 100 g DM. Statistical analyzes also showed a significant difference between the β-carotene contents. The Betacarotene determines the activity of vitamin A and is responsible for the orange color of tomato fruits [24]. The values obtained are lower than those of Rotino et al. [22] with values ranging from 49.11 to 69.85 mg / 100 g DM on four tomato genotypes. They are similar to those obtained by Georgé et al. [21] and Tudor-Radu et al. [23] with respective values of 17.4 and 9.26 to 33.40 mg / 100g MS. Like the lycopene content, the β-carotene content may also depend on several factors such as variety, degree of maturity and agronomic conditions [13,25].

Total Polyphenol Content (mg GEA / 100 g DM)
The total phenolic content was including between 502.84 ± 47.46 and 1181.08 ± 182.96 mg GEA / 100 g DM (Figure 2). The total phenolic content was including between 502.84 ± 47.46 and 1181.08 ± 182.96 mg GEA / 100 g DM. The results show that all the varieties studied are rich in total phenolic. The 25T2 variety is the richest one in total phenolic (1181.08 ± 182.96 mg GEA / 100 g DM), followed by the variety 31 M1T11 (1150.787 ± 158.58 mg GEA / 100 g DM) and of the 22 3T1 variety (972.998 ± 139.37 mg GEA / 100 g DM). The statistical analyzes show a significant difference between the varieties (P ≤ 0.05). The values found in the present in the present study are below than those reported by Tudor-Radu et al. [23] which ranged from 29911.50 to 42874.01mg of GEA / 100g DM. On the other hand, they are lower than the values of George et al. [21] on red tomato and those of Sahlin et al. [20] on two varieties (Excell, Aranca) with respective values of 268 mg and 354.83 to 438.6 mg GEA / 100 g DM. Also, they are above those obtained by Seremé et al. [26] for Burkina Faso tomato Mongal F1 with values of 157.33 to 193.47 mg GEA / 100 g DM. The variability in total phenolic content observed may be due to the very difference of the varieties and their degree of maturity. It may also be due to the solvent used during extraction of the total phenolic. In previous study on Hibiscus sabdariffa, Arthur et al. [27] demonstrate the variability in the content of phenolic compounds using three different solvent ((70: 30% v / v), ethanol / water (70: 30% v / v) and methanol-HCl (1%)) during extraction. The variability in total phenolic content may also depend on UV radiation and the stress on the tomato [28].

Correlation Between Lycopene and β-Carotene Contents
The results in table 3 show a very strong positive correlation between lycopene and β-carotene contents. This correlation is explained by the fact that for the same variety, if the lycopene content is high, the β-Carotene content is also high and if the lycopene content is low, the β-Carotene content is also low. There is a weak negative correlation between lycopene and total polyphenols and between β-Carotene and total polyphenols.

Hierarchical Ascending Classification of the Total Polyphenol Content
The

Conclusion
At the end of this study, it appears that the 45 tomato varieties present a good content of lycopene, β-carotene and total phenolic. These results shown that these varieties are potential sources of antioxidant. The highest levels of lycopene and β-carotene were observed in the BT1 of Brazil and M1T10 varieties of Mali compared to the other varieties. The determination of the total phenolic revealed that the 25T2 of Burkina Faso and M1T11 of Mali varieties had a large amount of total phenolic than the other varieties of tomatoes. Varieties with high levels of lycopene, ß-carotene and total phenolic could be advised by the producer for cultivation at the national level.