Comparative Phytochemical and Nutritional Composition of Trichosanthes cucumerina ( L . ) and Some Solanum lycopersicum ( L . ) Cultivars in Nigeria

The phytochemical and nutritional composition of Trichosanthes cucumerina L. an underutilized vegetable used as substitute for Solanaceous tomatoes by rural dwellers was examined in comparison with majorly cultivated tomato cultivars in Nigeria (Roma VF and Ibadan local). The fruit pulp of T. cucumerina was higher in carotenoid (2053.33 mg/100g), flavonoid (861.67 mg/100g), cardiac glycoside (11.67 mg/100g), alkaloids (93.33 mg/100g), lycopene (118.5 μg/100g), tannin (555.00 mg/100g), oxalate (2.55 mg/100g) and quercetin (5.25 mg/100g) than Roma VF and Ibadan local. However, Roma VF had the highest concentration of saponin (66.67 mg/100g) but there was no significant difference in steroid among the fruits. The Vitamins A, E and C contents of T. cucumerina (5346 μg/100g, 6.23 μg/100g and 25.33 μg/100g) were significantly higher (P < 0.05) than those in S. lycopersicum. T. cucumerina had the highest values of crude protein and crude lipid (1.97% and 0.40%). The fruit pulp of T. cucumerina also had the highest ash and total carbohydrate contents (1.63% and 16.50%). Roma VF was significantly higher in crude fibre and moisture contents (1.77% and 89.40%) than other vegetables investigated. All the evaluated mineral elements (Na, K, Ca Mg, Zn, Fe, Mn, P and S) in T. cucumerina compared favourably with S. lycopersicum cultivars. It was observed that T. cucumerina pulp contained an appreciable number of nutrients and secondary metabolites which qualify it as a good substitute to S. lycopersicum.


Introduction
Neglected Underutilized Species (NUS) were not receiving attention by mainstream agriculture for a variety of agronomic, genetic, economic, social and cultural reasons; today these crops are receiving increasing recognition because of their potential roles in mitigating risk of agricultural production systems and their nutritional quality [1].Trichosanthes cucumerina is an underutilized plant, the fruit of which is mainly consumed as a vegetable by rural dwellers most especially in western part of Africa.It is an annual climber belonging to the family Cucurbitaceae.It is commonly called snake gourd, viper gourd, snake tomato or long tomato [2].The endocarp pulp when fully mature is sweet tasting, aromatic and deep red which does not go sour as quickly as the paste of S. lycopersicum, this account for the reason why it is employed as an alternative to the Solanaceous tomato [3].
The plant is richly constituted with a series of secondary metabolites like flavonoids, carotenoids, phenolic acids which makes the plant pharmacologically and therapeutically active.It has a prominent place in alternative systems of medicine like Ayurveda and Siddha due to its various pharmacological activities like antidiabetic, hepatoprotective, anti-inflammatory, larvicidal effects [2] and cytotoxicity against some cancer lines [4].
Although, vegetables play a very important role as a source of nutrients to the human body and their consumption ensures intake of various essential vitamins and mineral elements thus avoiding the problem of malnutrition [5] but, less attention has been given to nutritional qualities of some underutilized vegetables.
As a result, diets deficient in essential vitamins and nutrients still persist in many parts of the world.
Previous scientific studies have reported some phytoconstituents and antioxidant activities of the fruit of T. cucumerina [6]; antidiabetic activities of the seed [7]; anti-inflammatory activity of the aerial part of T. cucumerina [8].However there are few scientific reports about minerals, proximate, vitamins and phytochemical compositions of this plant.This study therefore aimed at providing scientific information on the minerals, proximate, vitamins and phytochemical composition of Trichosanthes cucumerina in comparison with two common tomato cultivars in Nigeria (Roma VF and Ibadan local) with a view to establish its potential as a good substitute to the Solanaceous tomatoes.

Collection of Materials and Nursery Establishment
Two cultivars of mature and ripe S. lycopersicum fruits (Ibadan-local and Roma-VF) and T. cucumerina fruit pulps were used for this study.Seeds of S. lycopersicum cultivars were collected from the National Horticultural Research Institute (NIHORT), Jericho, Ibadan, Nigeria.T. cucumerina seeds were obtained from the Federal University of Agriculture, Abeokuta Botanical Garden, Nigeria (7˚11'51''N -32˚6'12'E).
The seedlings of S. lycopersicum cultivars and T. cucumerina were raised in trays filled with sterilized top soil of 10 kg each.They were watered twice daily and transplanted to the field four weeks after planting.The seedlings were raised in a loamy soil without application of fertilizer on a bed at a spacing of 60 x75 cm on one meter wide within and between rows as recommended by NIHORT Production Guide for Tomatoes at the Federal University of Agriculture Abeokuta Botanical Garden.Trellis was prepared for T. cucumerina with six sticks (2.5 m each), three in a row and one seedling to a stand.Mulching, weeding, staking and other horticultural operations were carried out.

Preparation of Samples
Ripe fruits of T. cucumerina and S. lycopercicum (cultivars) were harvested four months after planting.They were washed and the fruits of T. cucumerina were split open exposing their pulps which were extracted and S. lycopercicum (cultivars) fruits were cut into slices.The two fruits were oven dried to a constant weight at 60˚C in a Gallen camp electric oven.The dried samples were ground into powder and put in dried air tight containers and stored in a cool dry place.
The oven dried powder was extracted in Soxhlet's with distilled water.The extract obtained in the solvent was concentrated, distilling off the solvent and evaporate to dryness.The solvent free extract obtained was subjected to qualitative test for the identification of various plant constituent from the samples.

Phytochemical Screening of Plant Samples
The phytochemical components of the fruits of T. cucumerina and two Solanum lycopersicum cultivars were screened by using standard procedures as described by [9] [10] [11] [12].

Quantitative Determination of Phytochemicals in Plant Samples
Determination of Tannin Tannin was estimated by the method of [13].

Determination of Saponin
Saponin content was calculated as described by [14].Determination of Oxalate Oxalate was determined by using the titrimetric method described by [15].% Oxalic acid = Standard Value × Average Titre (0.02); 1 ml of 0.1 N KMnO 4 = 0.00450 g anhydrous oxalic acid.
Determination of Caroteniods Caroteniod content of samples was determined using spectrophotometric method of [16].

Determination of Flavonoids
The ethyl acetate precipitation method was used as described by [12].Determination of Lycopene Lycopene contents of the samples were determined using spectrophotometric evaluation method as described by [17].

Absorbance of sample Gradient factor Dilution factor Lycopene in g g
Wt. of sample taken in g µ × × = Determination of Cardiac glycosides Cardiac glycoside content of fruit samples was determined using spectrophotometric method of [16].
Determination of Steroid Estimation of steroid content of samples was carried out using method of Analytical Methods Committee of Royal Society of Chemistry [18].

Absorbance of Sample Gradient Dilution factor % Steroid
Weight of sample 10, 000 Determination of Quercetin Quercetin was determined by using spectrophotometric method [18].

Quercetin mg 100g
Absorbance of sample average gradient factor Dil. factor Weight of sample × × =

Moisture content
Thermal drying method was used in the determination of moisture content of the samples as reported by [19].Crude protein Determination Determination of crude protein was done by determining the total organic nitrogen using the macro-Kjeldhal method [20].
( ) % Crude Protein = % N 2 (Nitrogen) × 6.25 M = Actual Molarity of Acid; V = Titre Value (Volume) of HCl used; V t = Total volume of diluted digest; Va = Aliquot volume distilled (6.25 is a general factor suitable for products in which the proportions of specific proteins are not well defined).
Crude lipid Determination Determination of crude lipid content of the samples was done using Soxhlet type of the direct solvent extraction method [21].

Ash Determination
The ash content was determined using the ignition method [19].
M a = Mass of ash (g); M s = Mass of sample used (g).
Crude Fibre Determination Crude fibre was determined using the method of [19].
Calculation: The loss in weight on incineration = C 1 − C 2 .

Carbohydrate Determination
Total carbohydrate content of each sample was estimated by "difference".In this, the sum of the percentages of all the other proximate components was subtracted from 100 [22].

Vitamin Analysis
The vitamins (A, E and C) in the fruits of both T. cucumerina and S. lycopersicum (Roma VF and Ibadan local) were determined by the methods of the As- sociation of Official Analytical Chemists [19].

Determination of Mineral Composition
The samples were digested with concentrated nitric and percholoric acids.Potassium (K) and Sodium (Na) were determined with the aid of corning 400 flame photometer according to the method of [23].Phosphorus was determined using UV-visible Spectrophotometer (JASCO V-630) at 436 nm [19].Calcium (Ca), Magnesium (Mg), Zinc (Zn), Iron (Fe), Manganese (Mn) and Sulphur (S) were determined by Atomic Absorption Spectrophotometer (Model 3030 Perkin Elmer, Nortwalk, USA) according to the established procedures of [24].

Statistical Analysis
Data were subjected to analysis of variance (ANOVA); means of the samples were separated by Duncan Multiple Range Test (DMRT) at 5% level of probability using SPSS software version 17.0.

Results and Discussion
The results of the phytochemical screening conducted show that the extracts from the fruit samples contained tannins, carotenoids, flavonoids, saponins (Table 1).Negative results were recorded for alkaloids and lycopene in all the extracts except the fruit of T. cucumerina.Also oxalate, cardiac glycosides, steroids and quercetin were found absent in all the extracts of the three fruit samples.These phytochemicals were present in varying level in all the fruits.This variation in level of visibility may be due to quantity of the phytochemicals in the fruits while absence of phytochemical denotes minute presence of phytochemical which could not trigger qualitative changes due to the adopted method (Table 2).These phytochemicals play a crucial role in maintaining optimal immune response, such that deficient or excessive intakes can have negative impact on health [25].
The quantitative screening of these phytochemicals revealed significant differences (P < 0.05) among the extract of the fruit samples (Table 2).T. cucumerina had the highest contents of tannin, oxalate, carotenoids, flavonoids, alkalo- ids, lycopene, cardiac glycoside and quercetin.Roma VF cultivar had the highest value in saponin and steroid.All the fruits exhibit appreciable amount of carotenoid with the highest present in T. cucumerina ( 2053.33 mg 100g ) and the lowest in Roma VF (1345.00mg 100g ).The high carotenoid present in T. cucumerina fruit shows that the fruit has antioxidant properties which are asso- ciated with good health and reduced risk of diseases [26].The fruit pulp of T. cucumerina (118.53 g 100g µ ) also showed a considerable quantity of Lycopene-a derivative of carotenoid compared to S. lycopersicum cultivars examined.Lycopene is responsible for the red colour of fruits [27].It is a very good antioxidant that is associated with reduction in the risk of prostate cancer as reported by [28].The values of flavonoid and its derivative Quercetin in the fruits are significantly different (P < 0.05) with the peak value of flavonoid obtained in T. cucumerina ( 861.67 mg 100g ).This also make T. cucumerina potentially endowed with the capacity to carryout biological activities, such as anti-inflammatory, antiallergic, antischemic, immunomodulatory, and antitumoral activities [29] [30].
The results also showed that T. cucumerina had high quantity of alkaloid and cardiac glycosides compared to the mostly consumed tomato cultivars in Nigeria.Many alkaloids are pharmacologically active substances, which possess various physiological activities in both humans and animals [31].They also exhibit antibiotic activities, and form part of drugs used in the treatment of congestive heart failure in a moderate dose [32].
Meanwhile, the results of this study revealed that T. cucumerina also recorded highest value in the anti-nutritive concentration of tannin and oxalate but recorded lowest value of saponin as shown in Table 2.This is in agreement with the result of [33] when T. cucumerina was compared with Jatropha cucas and Citrillus vulgaris.These anti-nutrients could be toxic when consumed in an unprocessed food.However, at the present concentration they may not constitute major danger provided the fruits are cooked before consumption [34].Oxalates are leached out during the soaking, boiling and processing of the plant materials [35] [36].Despite the negative impact of these anti nutrients, tannins have been reported to be beneficial when applied to the mucosal lining of the mouth [37].They also exert some physiological effects such as acceleration of blood clotting, reduce blood pressure, decrease serum lipid level and modulate immunoresponses [38].
Vitamins A, E and C present in the fruit pulp of T. cucumerina were significantly higher than those of S. lycopersicum cultivars (Table 3).T. cucumerina pulp had the highest values of Vitamin A, E and C with the value of 5346.40 μg/100g, 6.23 μg/100g and 25.33 μg/100g respectively.Ibadan local showed the lowest value of Vitamins E and C with the value of 4.66 μg/100g and 22.47 μg/100g respectively while Roma VF had the lowest value of Vitamin A (4459.70 μg/100g).The results of this study agree with the report of [39] that T. cucumerina fruit pulp is a good source of Vitamins.Vitamin A, a derivative of beta ca- rotene helps to maintain good sight and prevent certain diseases of the eye [40].
Vitamin E helps maintain cell membrane, red blood cell integrity and also involved in immune function [41].Vitamin C also known as ascorbic acid promotes wound healing [40]; strengthens resistance to infections by boosting the immune system and improves absorption of iron [41] [42].
The proximate content of the fruits examined is shown in Table 4.The moisture in the fruit pulp of T. cucumerina and the two other tomato cultivars are high although varies significantly with highest volume reported to be that Roma VF (89.40%).The moisture content influences the rate of food absorption and digestion [43].Also high moisture content of the fruits indicates high water  retention capacity and could therefore easily be spoiled by fungi if not consumed on time [44].The fruits generally have low protein content (Table 4).The ether extract (crude fat) content of the fruit pulp of T. cucumerina (0.47%) was slightly higher than that of Roma VF and Ibadan local (0.30%) each.A diet providing 1% -2% of its caloric energy as fat is said to be sufficient to human beings as excess fat consumption yields certain cardio vascular disorder such as atherosclerosis, cancer and aging [45].From the result, the fruits contain little crude lipid which makes them very healthy for consumption.There are also significant differences for both ash and crude fibre contents of the fruit samples (Table 4).Ash on food determines largely the extent of mineral matters likely to be found on food substance [46].T. cucumerina has higher carbohydrate and lower fibre content than other Solanaceous tomato cultivars (Table 4).Carbohydrates and lipid are the principal sources of energy.The values of carbohydrates content in these samples per 100 g can provide a lower calorie of energy preventing the breakdown of the body's store of protein [46].
T. cucumerina fruits had highest percentage of all the analyzed minerals compared to the two Solanaceous tomato cultivars (Table 5).The quantity of the mineral elements ranges from Sodium to Manganese (Na-Mn) in all the fruit samples: T. cucumerina (1645.00-0.06 mg/100g), Roma VF (878.33 -0.02 mg/ 100g) and Ibadan local (948.33-0.03 mg/100g).This is in accordance with the study of [33] where manganese, sodium and iron were compared among T. cucumerina, Jatropha cucas and Citrillus vulgaris.
Mineral elements also play important roles in health and disease states of humans.For example, [47] reported that high amount of potassium in the body increases iron utilization.Calcium and phosphorous containing substances are required by children, pregnant and lactating woman for bones and teeth development [46].This result showed that T. cucumerina can contribute 341.66 mg of the recommended daily allowance of 800 mg of Ca and P required per day for both adults and children [48].Magnesium, a constituent of bones, teeth and enzyme cofactor [49] and Iron which is required for the formation of haemoglobin were found to be more in T. cucumerina compared to the Solanaceous tomato cultivars.
Zinc, Sulphur and Manganese were of low quantity in all the fruit samples.They are required for building immune system; regulation of cellular growth and acts as a co enzyme for carbohydrates, protein and nucleic acids metabolism; regulation of blood sugar level and production of energy [46].

Conclusion
This study has revealed that most of the phytochemicals, vitamins, proximate composition and mineral contents of T. cucumerina are high enough and compare favourably with the composition of those S. lycopersicum cultivars examined.T. cucumerina also have low and safe oxalate content, and other anti-nutrients which could leach out during cooking making it safe for consumption.This result recommends T. cucumerina for households, food industries and pharmaceutical industries utilization as a substitute for S. lycopersicum due to its high nutrient composition and its potential roles in medicare.

W 1 =
weight of empty filter paper; W 2 = weight of filter paper + paper precipitate Determination of Alkaloids The alkaloid content was determined gravimetrically[9].

W 1 =
weight of empty filter paper; W 2 = weight of filter paper + paper precipitate content; W o = Loss in weight (g) on drying; W i = Initial weight of sample (g).

Table 1 .
Qualitative phytochemical screening of T. cucumerina and two S. lycopersicum cultivars (Roma VF and Ibadan Local) fruits.

Table 2 .
Quantitative phytochemical screening of T. cucumerina and two S. lycopersicum cultivars (Roma VF and Ibadan Local) fruits.
cMean value in the same row having different alphabets are significantly different (P < 0.05).Data are means of triplicate determinations ± standard errors.

Table 3 .
Vitamins composition of T. cucumerina and two S. lycopersicum cultivars (Roma VF and Ibadan Local) fruits.

Table 4 .
Proximate composition of T. cucumerina and two S. lycopersicum cultivars (Roma VF and Ibadan Local) fruits.
bMean value in the same row having different alphabets are significantly different (P < 0.05).Data are means of triplicate determinations ± standard errors.

Table 5 .
Mineral elements of T. cucumerina and two S. lycopersicum cultivars (Roma VF and Ibadan Local) fruits.