INFLUENCE OF BIOREGULATORS AND SALINITY STRESS ON SOME BIOCHEMICAL, NUTRITIONAL AND ANTIDIABETIC PROPERTIES OF Abelmoschus esculentus LINN. (MOENCH

Abstract

Okra (Abelmoschus esculentus) is a commonly consumed vegetable and useful in ethnomedicine for the management of Diabetes mellitus. Bioregulators such as indole acetic acid (IAA) and salicylic acid (SA) play important roles in the growth and development of okra plant. There is paucity of information on bioregulator application to mitigate salinity stress effect on okra growth, and the use of okra in the management of Diabetes mellitus. This study was designed to assess the effects of bioregulators (IAA and SA) on growth and antidiabetic effect of salt-stressed okra. Two hundred okra seeds of genotypes 47-4 and LD88 were obtained from National Horticultural Research Institute, Ibadan. The seeds were divided into two equal parts each. Twenty-five seeds, part of each 47-4 and LD88, were soaked in IAA {0 (control), (0.4, 0.5, 0.6) mM} and another twenty-five seeds were soaked in SA {0, (10-2 , 10-4 , 10-6 ) mM}. The seeds (n=5) were planted in a complete randomized design each in 10 kg of soil contained each of 0, 50, 100, 150, and 200mM NaCl. Okra leaves and fruits were harvested for the analysis. Ethanol and aqueous extracts of IAA treated okra plant fruits (EEI and AEI), and that of extracts without IAA (EEW and AEW) were used to evaluate the activity of glucose transporter (GLUT)-14 in frog oocytes. Diabetes was induced in thirty male Sprague-Dawley rats (130-150 g) using streptozotocin (65mg/kg, i.v.) and grouped as: EEI, AEI, EEW, AEW, diabetes control, and glibenclamide (5mg/kg). Five non diabetic animals serve as control. The animals were orally treated with okra extracts (100mg/kg), control and diabetic control with 0.9% saline for six weeks, and then euthanized. Photosynthetic pigments, minerals, blood glucose, lipid profile, gluconeogenic enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were determined spectrophotometrically. Scintillation counter machine was used for GLUT-14 activity. Liver and muscle glycogen deposit were determined by Periodic Acid Schiff (PAS) stain technique. Results were analysed using ANOVA at α0.05. Chlorophyll b and carotenoids contents in LD88 leaves were increased (6.52±0.01 and 3.26±0.02 mg/gfw) at 200mM NaCl in 0.5mM IAA and at 50mM NaCl in 0.4mM IAA, respectively relative to controls. Similar effects were observed in the 47-4 genotype. The LD88 fruits calcium, potassium and zinc contents increased by 33.5, 37.1 and 36.9%, respectively at 10-4 mM SA in ii 50mM NaCl compared to controls. The EEI reduced blood glucose, total cholesterol, triglycerides, glucose-6-phosphatase and fructose-1,6-bisphosphatase by 25.0, 30.0, 25.0, 47.0 and 46.0%, respectively relative to controls. The EEI increased SOD, CAT and GPx in the liver (10.78±0.20, 63.85±4.19 and 12.51±0.44 U/mg), respectively. The GLUT-14 injected oocytes incubated in radiolabeled-glucose without extract, and with EEI showed high activities of GLUT-14 with mean uptake of 2-deoxy-D-glucose of 2840.2±829.5 and 2666.2±995.1 pmols/oocyte/15min, respectively relative to water injected oocytes (202.2±57.9 pmols/oocyte/15min). Liver and muscle glycogen deposit increased significantly in EEI-treated animals. Indole acetic acid and salicylic acid improved okra plant salt tolerance, yield and survival. Ethanol extract of indole acetic acid-treated okra fruits possessed hypoglycaemic property, therefore improved medicinal properties of okra fruits.