Res.J.Chem.Sci.______________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011) ISSN 2231-606X Proximate and Phytochemical Analyses of Solanum aethiopicum L. and Solanum macrocarpon L. Fruits Shalom Nwodo Chinedu, Abayomi C. Olasumbo, Okwuchukwu K. Eboji, Opeyemi C. Emiloju, Olajumoke K. Arinola and Damilola I. Dania Department of Biological Sciences, School of Natural and Applied Sciences, College of Science and Technology, Covenant University, Canaan land, PMB 1023 Ota, Ogun State, NIGERIA Available online at: www.isca.in (Received 26th April 2011, revised 4th May 2011, accepted 25th May 2011) Abstract Chemical analyses were carried out to determine the nutritional and phytochemical constituents of fruits of two indigenous Africa eggplants, S. aethiopicum L. and S. macrocarpon L. Proximate analysis of fresh fruits of S. aethiopicum L. (per 100 g) showed: 89.27 ± 0.12 g moisture, 2.24 ± 0.03 g protein, 0.52 ± 0.04 g fat, 0.87 ± 0.03 g ash, 2.96 ± 0.08 g crude fiber, 4.14 ± 0.11 g carbohydrate and 498.47 ± 2.14 mg calcium, 1.98 ± 0.10 mg magnesium and 1.02 ± 0.02 mg iron. Fresh fruits of S. macrocarpon L. contained (per 100 g): 92.50 ± 0.14 g moisture, 1.33 ± 0.05 g protein, 0.17 ± 0.01 g fat, 0.47 ± 0.02 g ash, 1.11 ± 0.03 g crude fiber, 4.42 ± 0.12 g carbohydrate, 101.56 ± 1.21 mg calcium, 1.01 ± 0.08 mg magnesium and 0.70 ± 0.01 mg iron. There was a significant presence of alkaloids, saponins, flavonoids, tannins and ascorbic acid in both fruits; terpenoids was found in trace amount. Steroids were present in S. aethiopicum L. and absent in S. macrocarpon L. These phytochemicals are of therapeutic importance; their presence in S. aethiopicum and S. macrocarpon fruits indicate the beneficial effects of the plants. Solanum aethiopicum L. contained higher levels of the beneficial agents than S. macrocarpon L. The two indigenous eggplants are not only nutritionally and therapeutically valuable, but also have the potential of providing precursors for the synthesis of useful drugs. Keywords: African eggplants, solanum aethiopicum L., solanum macrocarpon L.proximate composition, phytochemicals. Introduction Solanum, a widespread plant genus of the family Solanaceae, has over 1000 species worldwide with at least 100 indigenous species in Africa and adjacent islands; these include a number of valuable crop plants and some poisonous ones. It is represented in Nigeria by some 25 species including those domesticated with their leaves, fruits or both eaten as vegetables or used in traditional medicine.2,3 Among them aretwo African eggplants, S. aethiopicum L.(Ethiopian eggplant) and S. macrocarpon L. (Gboma eggplant), which are widely cultivated in Nigeria and across the African continent.4-6 African eggplants, also called garden eggs (Hausa: Dauta; Igbo: afufa or añara; Yoruba: igbagba), are highly valued constituents of the Nigerian foods and indigenous medicines; they are commonly consumed almost on daily basis by both rural and urban families. The eggplants form part of the traditional sub-Saharan African culture. The fruits, said to represent blessings and fruitfulness, are offered as a token of goodwill during visits, marriages and other social events. They are eaten raw and also when boiled or fried as ingredient of stews, soups and vegetable sauces. Wide variations exist within the vegetative and fruit characters both within and between the African eggplant species including variations in characters like diameter of corolla, petiole length, leaf blade width, plant branching, fruit shape, and fruit colour. Their uses in indigenous medicine range from weight reduction to treatment of several ailments Res.J.Chem.Sci.______________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011) ISSN 2231-606X including asthma, allergic rhinitis, nasal catarrh, skin infections, rheumatic disease and swollen joint pains, gastro-esophageal reflux disease, constipation, dyspepsia.9,10 Several studies support the folkloric use of the plants in local foods and medicinal preparations; for instance, different researchers have reported significant analgesic, anti-inflammatory, anti-asthmatic, anti-glaucoma, hypoglycemic, hypolipidemic, and weight reduction effects of eggplants, particularly S. melongena, on test animals and humans.9,11-13 These pharmacological properties have been attributed to the presence of certain chemical substances in the plants, such as fiber, ascorbic acid, phenols, anthocyanin, glycoalkaloidsand -chaconine.14,15 In this study, proximate and phytochemical analyses were carried out on two indigenous eggplants, S. aethiopicum L. and S. macrocarpon L., and used to assess their potential nutritive and medicinal benefits. Material and Methods Collection and Identification of specimens: Fruits of S. aethiopicum L. and S. macrocarpon L. were purchased from Mile 12 market in Lagos, Southwest Nigeria. The fruits were identified and authenticated in the Department of Biological Sciences of Covenant University by a botanist, Mr. C. A. Omohinmin. Voucher specimens were also deposited at the Department. The fruits were selected and thoroughly washed in water to remove dirt and unwanted particles. The stalks were removed and the edible portion of the fruits was analyzed. Proximate Analysis: Proximate composition of the fruits was determined by the official method of the Association of Official Analytical Chemists as follows: Moisture (section 926.08 and 925.09), Protein (section 955.04C and 979.09), Fat (section 922.06 and 954.02), ash (section 923.03) and crude fiber (section 962.09)16. Carbohydrate was calculated by difference. Analysis of mineral contents: Five grams (5 g) of the sample was dry-ashed in an electric furnace at 550C for 24 hours. The resulting ash was cooled in a desiccator and weighed. The ash was dissolved with 2 ml of concentrated HCl and few drops of concentrated HNO were added. The solution was placed in boiling water bath and evaporated almost to dryness. The content was then transferred to 100 ml volumetric flask and diluted to volume with deionized water. Appropriate dilutions were made for each element before analysis. Calcium, magnesium and iron contents were quantified using S series atomic absorption spectrophotometer as described in the official method of the Association of Official Analytical Chemists.16 Phytochemical screening: Samples were sun-dried, pulverized and passed through a sieve (about 0.5 mm pore size) to obtain a fine dry powder. Aqueous extract of the sample was prepared by soaking 100 g of the powdered samples in 200 ml of distilled water for 12 hours. The extracts were filtered using Whatman filter paper No 42 (125 mm). Chemical tests were carried out on the aqueous extract and on the powdered samples to identify the constituents using standard procedures.17-19 Colour intensity was used to categorize the presence of each phytochemical into copious, moderate or slight (trace). Test for Alkaloids: About 0.5 g of crude powder was defatted with 5% ethyl ether for 15 minutes. The defatted sample was extracted for 20 min with 5 ml of aqueous HCl on a boiling water bath. The resulting mixture was centrifuged for 10 minutes at 3000 rpm. One milliliter (1 ml) of the filtrate was treated with few drops of Mayer’s reagent and another 1 ml with Dragendroff’s reagent and turbidity was observed17,19. Test for tannins: About 0.5 g of the dried powdered samples was boiled in 20 ml of water in a test tube and then filtered. A few drops of 0.1% ferric chloride was added and observed for brownish green or a blue-black coloration.Test for terpenoids: (Salkowski test): Five milliliters (5 ml) of the extract was mixed in 2 ml of chloroform, and 3 ml concentrated HSO was Res.J.Chem.Sci.______________________________________________Research Journal of Chemical Sciences Vol. 1(3) June (2011) ISSN 2231-606X carefully added to form a layer. A reddish brown coloration of the inter face was formed to show positive results for the presence of terpenoids. Test for cardiac glycosides (Keller-Killani test): Five milliliters (5 ml) of the extracts was treated with 2 ml of glacial acetic acid containing one drop of ferric chloride solution. This was underlayed with 1 ml of concentrated sulphuric acid. A brown ring of the interface indicates a deoxysugar characteristic of cardenolides. A violet ring may appear below the brown ring, while in the acetic acid layer, a greenish ring may form just gradually throughout thin layer.Test for steroids: Two ml of acetic anhydride was added to 0.5 g ethanolic extract of the sample with 2 ml HSO. The colour changed from violet to blue or green in some samples indicating the presence of steroids.Test for saponins: About 2 g of the powdered sample was boiled in 20 ml of distilled water in a water bath and filtered. 10ml of the filtrate was mixed with 5 ml of distilled water and shaken vigorously for a stable persistent froth. The frothing was mixed with 3 drops of olive oil and shaken vigorously, then observed for the formation of emulsion.Test for flavonoids: The presence of flavonoids in the plant sample was determined by the methods described by Sofowara and Harborne17,18. Five milliliter (5 ml) of dilute ammonia solution was added to a portion of the aqueous filtrate of the plant extract followed by addition of concentrated HSO. A yellow coloration observed in each extract indicated the presence of flavonoids. The yellow coloration disappeared on standing. Few drops of 1% aluminum solution were added to a portion of each filtrate. A yellow coloration was observed indicating the presence of flavonoids. A portion of the powdered plant sample was in each case heated with 10 ml of ethyl acetate over a steam bath for 3 min. The mixture was filtered and 4 ml of the filtrate was shaken with 1 ml of dilute ammonia solution. A yellow coloration is positive for flavonoids.Test for phytosterol: The aqueous extract was refluxed with solution of alcoholic potassium hydroxide till complete saponification takes place. The mixture was diluted and extracted with ether. The ether layer was evaporated and the residues were tested for the presence of phytosterol. The residue was dissolved in few drops of diluted acetic acid; 3ml of acetic anhydride was followed by few drops of conc. HSO. A bluish green color indicates the presence of phytosterol. Test for Ascorbic acid: Iodine solution consisting of 0.5g of iodine dissolved in 100ml of 1% potassium iodide solution was freshly prepared. One drop of the iodine solution was added into 1ml of 0.1% starch solution placed in a suitable receptacle. Aqueous extract of the sample was added drop by drop until the blue-black colour of the starch iodine complex disappears leaving a colourless solution. The colourless solution indicates the presence of ascorbic acid. Results Fruits of S. aethiopicum L. and S. macrocarpon L. are shown in plates 1 and 2. Solanum aethiopicum L. fruits were mostly round shaped, medium or large sized and dark green in colour. Fruits of S. macrocarpon L. were oval shaped with a mixture of cream white to light yellow and green with dark green stripes. Table 1 shows the approximate composition of S. aethiopicum L. and S. macrocarpon L. fruits. The nutrient and mineral composition of S. aethiopicum L. fruits per 100 g fresh sample is as follows: 89.27 ± 0.12 g moisture, 2.24 ± 0.03 g protein, 0.52 ± 0.04 g fat, 0.87 ± 0.03 g ash, 2.96 ± 0.08 g crude fiber, 4.14 ± 0.11 g carbohydrate, 498.47 ± 2.14 mg calcium, 1.98 ± 0.10 mg magnesium and 1.02 ± 0.02 mg iron. Solanum macrocarpon L. contained per 100g fresh fruit: 92.50 ± 0.14 g moisture, 1.33 ± 0.05 g protein, 0.17 ± 0.01 g fat, 0.47 ± 0.02 g ash, 1.11 ± 0.03 g crude fiber, 4.42 ± 0.12 g carbohydrate, 101.56 ± 1.21 mg calcium, 1.01 ± 0.08 mg magnesium and 0.07 ± 0.01 iron. Result of the phytochemical screening of the fruits is contained in Table 2. There was copious presence of alkaloids, flavonoids,