Nutrients, Phytochemical Compositions of Hibiscus Cannabinus, Adansonia Digitata, Sesamum Indicum, Cassia Tora Leaves, Their Hypoglycemic Activity and Lipid Profile in Alloxan-Induced Diabeti

ABSTRACT The study investigated the nutrients and phytochemical compositions of some leafy vegetables in Nigeria (Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves) and the effects of their extracts on blood glucose and lipid profile of alloxan induced diabetic rats. Two kilogrammes of each of the vegetables were bought fresh, sorted by removing extraneous material, washed with deionized water and separately pulverized using Gallenkamp mixer Kenwood –MPR 201. A half of the vegetables was used for chemical analysis and a half for methanol extract production. Standard methods were used to determine in triplicate the proximate, some minerals, vitamins, antinutrients, food toxicants, and phytochemical constituents of the fresh leaves and their methanol extracts. Animal study was carried out to ascertain the effect of the nutrients on blood glucose and lipid profile of alloxan- induced diabetic rats. Forty five male adult albino rats (150-200g) divided into nine groups of five rats each on basis of body weights were used for the study. The group of rats fed rat chow and glibanclamide drug served as standard control. The other groups were fed rat chow and graded doses of each vegetable extract (500mg and 1000mg/kg bodyweight) daily for twelve days. Water was given ad libitum. The proximate principles were lower in the fresh leaves than in the extract except for crude fibre. The leaves had 80.20% - 95.09% moisture, 1.62% – 3. 89% protein, 0.05% – 0.06% fat, 0.06% – 1.35% ash, 1.56% – 4.16 crude fibre and 1.04% – 13.71% carbohydrate. Mineral values were 236.68 – 437.11mg sodium, 0.87 – 2.67mg potassium, 0.63 - 4.97mg calcium, 172.50 – 235.70mg phosphorus, 0.51 – 0.59mg zinc, 0.26 – 0.59mg iron, 3.37 – 3.44mg copper and 0.24 – 0.28mg magnesium. The leaves contained 11.57 - 22.28 µg beta carotene, 1.25 - 2.88mg thiamin, 0.87 - 2.82mg riboflavin, 15.60 - 29.37mg vitamin C, niacin 0.74 - 1.61mg and 25.89 -31.43mg vitamin E. All the vegetables had traces of oxalate, 0.01mg - 0.05mg phytate, 0.37mg - 0.43mg tannins. Hydrocyanides levels of the vegetables were low (0.01 - 0.02mg). Food toxicants (cadmium and lead) levels of the leaves were (0.01 - 0.03mg and 0.02 - 0.14mg, respectively). The values were within safe levels for cadmium and lead allowed by World Health Orginisation (WHO) standard for food substances (SAFS). The phytochemicals of the vegetables were in small quantities relative to the nutrients. The phytochemical levels were higher in the extracts than in the fresh leaves. The leaves contained 0.06 - 0.12mg saponins; 0.01mg - 0.04mg flavonoids, 0.03mg – 0.21mg alkaloids, 0.01 – 0.02mg glycosides; 0.09mg - 0.21mg terpenes and 0.09mg - 0.16mg phytosterols. The extracts had 5.40% – 9.84% moisture, 14.56% - 26.42% protein, 0.68% – 1.23 % fat; 4.34% – xviii 8.51% ash, 0.62% – 0.83% crude fibre and 54.64% - 74.44% carbohydrate. Mineral values for the extracts were 873.64 – 1423.44mg sodium, 1122.61 – 1425.30 mg potassium, 1571.94 – 1924.34 calcium, 138.37 – 224.19mg phosphorus, 0.18 – 0.27mg/100g zinc, 18.74 – 34.19mg iron, 0.28 – 0.83mg copper, and 229.37 – 341.55mg/ magnesium. The extracts contained 7.60 – 13.70µg β carotene, 1.22mg - 2.40mg thiamin, 0.54 – 2.32mg riboflavin, 14.86 – 26.34mg vitamin C, 0.84 – 9.52mg niacin and 21.30mg - 25.72 mg vitamin E. The antinutrients contents of the extracts were 0.66mg - 1.78mg phytate, 4.57 - 7.07mg tannins and 0.22mg - 0.48mg hydrocyanides. 0.01mg - 0.03mg cadmium and 0.02mg – 0.21mg lead. Phytochemicals value for the extracts were 2.40 - 3.73mg saponins, 0.09 - 0.29mg flavonoids, 4.91mg - 6.77mg alkaloids, 2.40 - 3.84mg glycosides, 1.09mg - 2.30mg terpenes and 1.26mg - 2.50mg phytosterols. Feeding the rats with rat chow supplemented with graded doses of Hibiscus cannabinus, Adansonia digitata, Sesamum indicum and Cassia tora leaves extracts reduced blood glucose concentrations and improved lipid profiles. The Adansonia digitata and Cassia tora leaf extracts fed at higher doses (1000mg) decreased blood glucose concentrations of rats (33.63% and 23.92%, respectively) more than those fed standard antidiabetic drug glibenclamide (17.23% ). They improved lipid profile of the rats by (26.92% and 25.46%). They decreased the total cholesterol (TC) and triglyceride (TG)) 54.72 and 67.70% respectively more than those fed standard drug (21.15% TC and 45.83% TG). The vegetables extracts could be used for management of diabetes and some other related non – communicable diseases due to their rich nutrients, antioxidants and phytochemical constituents.