Indian J Physiol Pharmacol 1999; 43 (3): 510-514

HYPOGLYCAEMIC AND ANTI-OXIDANT ACTIVITY OF OBLONGA WALL. EXTRACT IN STREPTOZOTOCIN­ INDUCED DIABETIC RATS

K. KRISHNAKUMAR*, K. T. AUGUSTI** AND P. L. VIJAYAMMAL

Department of Biochemistry, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581 and

¥,." School of Medical Education, M.G. University, Medical College Campus, Kottayam - 686 008

(Received on February 20, 1999)

Abstract: The petroleum ether extract of the root bark of S. oblonga WaIL (Celastraceael (SOB) was studied in streptozotocin (STZ) diabetic rats and anti-lipid peroxidative activity of the same was studied in the cardiac tissue. SOB prevented significantly the streptozotocin-induced hyperglycaemia and hypoinsulinaemia. It also produced a significant decrease in peroxidation products viz. thiobarbituric acid reactive substances (P

Key words: Salacia oblonga hypoglycaemia lipid peroxidation antioxidant enzymes streptozotocin diabetes

INTRODUCTION (4, 5). Root bark boiled in oil or as decoction or as powder is used for the S. oblonga Wall. () is treatment of rheumatism, gonorrhoea, commonly known as 'ponkoranti' In itches, asthma, thirst and ear diseases Malayalam due to its golden coloured root (6). Oral administration of root bark bark. In Indian traditional medicine, the powder showed anti-inflammatory root bark of S. oblonga is used In activity (7). In the light of the above gonorrhoea, rheumatism and skin diseases reports the anti-diabetic activity of S. (1, 2, 3). The aqueous extract of the root oblonga root bark in hyperglycaemic rats bark has shown hypoglycaemic activity was studied.

*Corresponding Author Indian J Physial Pharmacal 1999; 43(4) Hypaglycaemic and Anti-Oxidant Activity 511

As there is growing literature on the with the pH having been adjusted to 4.5 toxic effects of oxygen free radicals and with 0.05M citric acid (11). After one week cardiovascular complications (8) especially glucose was measured in blood samples in diabetic condition (9) and to determine collected from orbital plexus. Rats with the mechanism of action of this drug, the glucose levels above 200 mg/dl were included level of lipid peroxides viz. thiobarbituric in the experiment. acid reactive substances, conjugated dienes, hydroperoxides, antioxidant glutathione Experimental procedure content, the related antioxidant enzymes superoxide dismutase (SOD), catalase, GSH The animal were divided into 5 groups Pxase, GSSG Rase etc. in the cardiac tissue of 6 animals each. Group I control rats were also studied. injected with 0.5 ml of physiological saline, group II rats were streptozotocin treated METHODS rats, group III diabetic rats given petroleum ether extract orally (hereafter referred to Animals as SOB) 250 mglkg of body weight daily, group IV diabetic rats received Female albino rats (Sprague-Dawley glibenc1amide (Hoechst, ) orally strain) from inbred stock having average (600 flglkg/day) and group V diabetic rats body weight 200 g were used for the received bovine insulin (Knoll Pharma, experiments. India) subcutaneously (6 units/kg). The duration of the experiment was one month. material and extraction At the end of the period the animals were deprived of food overnight and sacrificed by S. oblonga root was collected from decapitation. Western Ghats (8° 13' 38" Nand 77° 30' 16" E, Altitude-505 m), Thovalai, Kanyakumari Estimation of glucose and insulin District, Tamil Nadu, South India. The bark was removed from the root (yield 150 glkg) and powdered in an electric grinder. The Blood glucose was determined by the powder of bark was subjected to Soxhlet glucose oxidase method (12). The insulin extraction for 16 h with the following assay was done with a radioimmunoassay solvents sequentially: petroleum ether (60­ kit (Coat-A-Count(~J, DPC, Los Angeles) by 80), chloroform, acetone, methanol and the method of Morgan and Lazarow (13). water (0). The yield of the extract was 2.81, 0.02, 5.11, 2.66, 16.00% (w/w in terms of Estimation of peroxidation products and dried starting material) respectively. antioxidants

Experimental diabetes The levels of peroxidation products V1Z. thiobarbituric acid reactive substances Diabetes was induced by 65 mg/kg of (TBARS), conjugated dienes (CD) and streptozotocin administered i.p. in saline hydroperoxides (HP), glutathione (GSH) and 512 Krishnakumar et al Indian J Physiol Pharmacol 1999; 43(4) activity of antioxidant enzymes: superoxide RESULTS dismu.tase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), glutathione reductase Blood glucose (GSSGRase, EC 1.6.4.2) and glutathione peroxidase (GSHPxase, EC 1.11.1.9) were The hyperglycaemic animals showed estimated in the cardiac tissue as reported significant decrease in the blood glucose earlier (14). The protein content of the level on long term treatment for one month enzyme extract was determined by Lowry's with SOB at a dose of 250 mglkg (Group method (15). III). The glibenclamide and insulin treatment also produced significant decrease Data analyses in glucose levels in streptozotocin-diabetic rats. The activity of SOB was about 65.5% Statistical analysis was done using the of glibenclamide activity and 49.9% of the student's 't' test for glucose estimation, other insulin. The serum levels of insulin were parameters were analysed by one way increased significantly in SOB treated group analysis of variance CANOVA) and difference (Table 1). between treatment means were determined by Bonferroni multiple comparison Lipid peroxide concentration procedure. The concentration of TBARS, CD and HP Drugs and chemicals were significantly decreased in the SOB treated group as compared to the diabetic All the biochemicals used in this control (Table n. experiment were purchased from Sigma Chemical Company Inc., St. Louis, MO, USA Glutathione content unless otherwise specified. The chemicals were of analytical grade. The GSH content was increased III the

TABLE I Concentration of lipid peroxides, blood glucose, glutathione and insulin.

Group TBARS* Conjugated Hydroperoxides '.< GSH* Serum Glucose ** Serum dienes* Insulin ***

O.402±O.Ol 15.12±O.54 13.68±O.37 405.48±13.9 78.2±5.9 75.36±5.8

II O.521±O.O1" 20.01±O.67" 18.15±O.51" 357.86±9.5' 387.0±29.3a 24.55±2.0"

III O.476±O.Ol" 18.96±O.65' 16.26±O.80" 379.31±12.9' 197.2±14.0b 58.08±4.9"

IV O.445±O.Ol" 18.89±O.67' 15.51±O.92b 383.41±13.0' 153.6±11.P 59.93±4.9

V O.436±O.Ol" 17.10±O.59b 14.61±O.42b 391.21±13.2' 107.3±7.2b

Each value is the meRn ± S.D of 6 rats. "P

TABLE II Activity of the antioxidant enzymes.

Group SOD" Catalase** GSH Pxase*"" GSSG Rase****

I 12.99±0.35 8.16±0.54 0.79±0.1l 4.46±0.57 II 7.09±0.06' 5.18±0.15a 0.67±0.08" 2.94±0.37" III 8.04±0.2Ib 5.95±0.38" 0.70±0.09 3.04±0.39 IV 8.27±0.22b 6.85±0.44" 0.71±0.10 3.85±0.49 V 9.37±0.23b 7.05±0.45b 0.86±0.12b 3.34±0.43b

Each value is the mean ± S.D of 6 rats. *P

SOB, glibenclamide and insulin groups as streptozotocin diabetic rats and lipid compared to diabetic control (Table 1). peroxidation is one of the characteristic features of chronic diabetes (17). The Activity of anti-oxidant enzymes increased levels of thiobarbituric acid reactive substances (TBARS), conjugated The activity of SOD and catalase was dienes (CD) and hydroperoxides are indices significantly increased in treated groups of lipid peroxidation. The levels of TBARS, (Group III, IV and V). But the activity of CD and HP were decreased significantly in enzymes GSHPxase and GSSGRase showed the cardiac tissue of rats given SOB, significant increase in insulin and glibenclamide and insulin as compared to glibenclamide treated groups, but non­ the diabetic control animals where the levels significant changes in SOB treated group were quite high (Table 1). This indicates (Table II). that SOB may inhibit oxidative damage of the cardiac tissue. DISCUSSION

Under W VLVO condition, glutathione The experiments reveal that SOB (GSH) acts as an antioxidant and its (250 mg/kg) significantly (P

In conclusion, the above observations' The authors are grateful to the Science show that the petroleum ether soluble and Technology, Govt. of Kerala (India) for fraction of S. oblonga root bark (SOB) financial assistance.

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