Antidiabetic Effect of Urena lobata: Preliminary Study on Hexane, Ethanolic, and Aqueous Leaf Extracts

Chronic hyperglycemia is one of the signs of human type-2 diabetes mellitus due to insulin resistance and depletion. This study aimed to evaluate hexane, ethanolic, and aqueous leaf extracts of Urena lobata as antihyperglycemic agent. Design of this study was a post-test only control group using 25 male Sprague-Dawley rats divided into 5 groups. High fructose diet (HFD) ad libitum and single dose of intraperitoneal streptozocin (STZ) (25 mg/kgBW) were administered to induce diabetes in rats. Three groups of the diabetic rats orally received 500 mg/kgBW of only a type of leaf extract of U. lobata for 4 weeks. Insulin serum levels were measured using enzyme-linked immunosorbent assay (ELISA) method. Size, shape, and density of the islet cells were observed by light microscope. Blood glucose level and the area under curve (AUC) of serial oral glucose tolerance test (OGTT) were measured. The U. lobata leaf extracts of three types of solvent all increased serum insulin level and improved β cells condition, also decreased the AUC of the OGTT series in diabetic rats. Values were compared with untreated diabetic rats (p<0,05). The aqueous leaf extract of U. lobata was the best in increasing insulin serum level, recovering islet cells condition, and correcting blood glucose level. The hexane extract showed poor results when compared to the other soluble agents.


INTRODUCTION
experiment). The diabetic rats continuously received HFD until the study ended. Three groups of the diabetic rats Urena lobata otherwise called pulutan (Javaneseusing gastric sonde received hexane extract (HEU), Indonesia) is shrub growing well in the paddy field of ethanolic extract (EEU), and aqueous extract (AEU) of U. tropical region and growing well at elevations up to 1500 lobata at a dose of 500mg/kgBW every day for 4 weeks. m above sea level (1). One hundred grams of raw leaf Random and overnight fasting blood glucose level and oral contain 81,8% moisture, 54 calories, 3,2g of 57 protein, glucose tolerance test (OGTT) were measured. Glucose at 0,1g fat, 12,8g carbohydrates, 1,8g fiber, 2,1g ash, 558mg a dose of 2g/kgBW was orally administered prior to blood calcium, and 67mg of phosphorous (2). Combination of U.
glucose measurement at 15, 30, 60, and 120 minutes to lobata roots and Ennicostemma axillare (E. axillare) was present serial values of OGTT. reported to reduce spermatogenesis and steroidogenesis Glucose and Insulin Detection reversibly in adult male Wistar albino rats (3). Methanolic extract of U. lobata root at dose of 125-1000μg/ml Blood was taken from the tail vein. Blood glucose levels showed concentration-dependent antibacterial activity were measured by glucometer (Accu-Chek) (11). against some strains of Gram+ and Gram− (4). Root and Intracardial blood was collected from ketalar anesthesia leaf extracts of U. lobata have been used by Nigerian rats. Blood samples were immediately centrifuged at people to treat diabetes mellitus, a preclinical study of the 4500rpm, and serum was separated and stored under plant root and leaf extract showed an anti-hyperglycemic 20°C. Insulin serum levels were measured using a rat effect on streptozocin (STZ) induced rats (5).
insulin enzyme-linked immunosorbent assay (ELISA) kit. A Phytochemical screening of 95% ethanolic extract of aerial 50μl serum sample added with 50μl biotinylated detection parts of the plant showed the presence of alkaloids, antibody was subsequently incubated for 45 minutes at glycosides, steroids, tannins, saponins, and reducing 37°C. After being aspirated and washed, the samples were sugars (6). Aqueous extract of U. lobata exhibited an added with 100μl Horse dish peroxidase (HRP)-conjugated inhibitory effect of dipeptidyl peptidase IV (DPP-IV) anti-rabbit IgG prior to incubation at 37°C for 30 minutes. inhibiting glucagon like peptide-1 (7). Long-term Substrate reagent (90μl) was added to the samples and administration (daily for 24 weeks) of aqueous extract of then incubated for 15 minutes at 37°C. Finally, 50μl of 'stop the plant roots toward weaned rabbits (New Zealand solution' was added into samples which were then read strain) was reported to protect the pancreas from with a microplate reader at λ 450nm. oxidative stress (8). Ethanolic extract of the plant at a dose Microscopic Preparation of Pancreatic-Β Cells of 250mg/kgBW exhibited antidepressant and antiinflammatory (9). This study examined the anti-diabetic Pancreatic tissue slices were stained with Hematoxylin effect of U. lobata leaf extracted by different solvents, Eosin. Using light microscope (400x magnification), the namely; hexane, ethanol, and water. slides were observed for shape, size, and depiction of the number of pancreatic-β cells.

Data Analysis Preparation of U. Lobata Leaf Extract
Data were analyzed by using one-way ANOVA and Least Significant Difference test. P<0,05 was considered to be The leaf powder was obtained from Balai Materia Medica, significant. The data were expressed as means ±S.E.M Batu, Malang with certificate No. 074/027/101.8/2015. Decoction method was used to obtain an aqueous extract. In brief, the powder (50 g) was extracted in 250ml of 90°C RESULTS water for 30 minutes. Hexane and ethanolic extracts were The Effects of U. lobata Leaf Extract on Body Weight, Food prepared by using a shaking water bath at 40°C for 6 hours.
Consumption, Fasting and Random Blood Glucose Levels The extracts were then evaporated to obtain concentrated extracts. The extraction was done at In this study, hyperglycemia reduced body weights of temperature below the boiling point of each solvent. diabetic rats ( Table 1). The extracts of U. lobata leaf reduced body weight of diabetic rats, compared with the Animals and Treatments diabetic group receiving no extracts (p>0,05) ( Table 1). The Twenty five male Sprague-Dawley rats weighed 180-200g reduction of food consumption was detected in diabetic were obtained from Gadjah Mada University, Yogyakarta, rats administered with aqueous and hexane extracts of U. Indonesia. The animals were maintained under the lobata leaf compared with non-treated diabetic rats condition in accordance with the ethical clearance (p<0,05) ( Table 1). In this study, hyperglycemia did not obtained from the Commission of Ethical Research of influence the appetite of diabetic rats receiving no extract Brawijaya University, Malang, Indonesia, certificate No. and of diabetic rats receiving ethanolic extract of U. lobata 683-KEP-UB. The rats were separately housed into 5 (p>0,05). The three kinds of U. lobata leaf extracts groups and accommodated in an automatically controlled decreased fasting and random blood glucose levels 12:12-hour-light-dark cycle room. Free access to food and compared to diabetic rats received no extracts (p<0,05). water was available. Normal diet (ND) and high-fructose The aqueous extract has lead in reducing fasting and diet (HFD) were freshly prepared in a single alternate day. random blood glucose followed by the ethanolic extract, HFD contained 65% fructose and 35% ND. Intraperitoneal then the hexane extract ( Table 1). injection of a single dose (25mg/kgBW) of STZ followed by The Effects of U. lobata leaf Extract On Insulin Serum Level free access to HFD were conducted to induce diabetes in Of Diabetic Rats rats (fasting blood glucose was more than 126mg/dL) (10), diabetic conditions were detected in most of the animals 4 A significant decrease of insulin serum levels (14 folds) was weeks post-STZ injection. There were 4 diabetic groups shown in diabetic rats compared to normal rats (

Effect of U. lobata Extracts on Pancreatic Β-Cells of Diabetic Rats
Pancreatic islet β cells were examined using light showed pancreatic islet tissues with small numbers of long lobata leaf shape and unnucleated β-cells (Fig. 3). The extract of U.
Note: Measurements are expressed as Means ± S.E.M. a, b, c: different lobata leaf improved pancreatic islet tissues, the islet βletter indicates statistically significant difference (p<0,05). cells returned to be round in shape with slightly increased size. There was increased density of islet β cells of diabetic rats administered with the extract of the plant compared with that of type-2 diabetic rats. Slightly increased size of The Effect of U. lobata Extracts on Fasting and Random islet β cells indicated inflammation process in the Blood Glucose Levels, also Glucose Tolerance Test of pancreatic islet tissue (Fig. 3). The islet β cells quality of Diabetic Rats diabetic rats treated with aqueous extract of U. lobata was The U. lobata leaf extract reduced fasting and random the best. It was shown by the normal shapes and density of blood glucose levels of diabetic rats (p<0,05) ( Table 1). The islet β-cells which were proximal to that of healthy rats. area under-glucose tolerance test curve of diabetic rats was significantly corrected in diabetic rats treated with the extract of U. lobata leaf (fig. 2). The given dose of aqueous extract of U. lobata leaf was the most effective to correct blood glucose level in diabetic rats. At the same dose, the ethanolic extract corrected the blood glucose level close to the blood glucose level of healthy rats (p>0,05) (Fig. 2). The hexane extract of U. lobata leaf reduced blood glucose level significantly compared to the blood glucose level of untreated diabetic rats. Unfortunately, the blood glucose level was still higher than that of the healthy rats (p<0,05) (Fig. 2).

of Islet Β-Cells of Diabetic Rats
The extracts of U. lobata significantly increased insulin synthesis of type-2 diabetic rats (Fig. 1). The improvement of insulin synthesis was parallel with the condition of pancreatic islet β-cells as indicated by the increased densities of islet β-cells ( Fig. 1 and Fig. 3). The extracts also prevented islet β-cells to change in shape (Fig 3). The synergistic interaction of active compounds of U. lobata extract is suggested to have a role to increase insulin production (10). The improvement of β-cells morphology 15). A potent insulinotropic hormone, Glucagon-like peptide-1 (GLP-1), is released by oral glucose as well as DISCUSSION ingestion of mixed meals, the hormone is rapidly metabolized by Dipeptidyl peptidase (DPP) IV (12). In silico It was observed that hexane, ethanolic, and aqueous study reported that DPP IV activity was inhibited by extracts of U. lobata leaf reduced the body weight of aqueous and ethanolic extrats of U. lobata, it was diabetic rats (p<0,05) compared with diabetic rats supposed that bioactive compound of U. lobata may have received no extract ( Table 1). The previous study showed a property of DPP-IV inhibitor (7). Hormone GLP-1 inhibits aqueous extract of U. lobata root significantly reduced the gastric juice secretion and gastric motility, the later slows body weight in rabbits (10). Hexane and aqueous extracts gastric emptying rate and prolongs the transportation of of the plant leaf reduced food consumption of diabetic gastric juice into the gut that consequently prevents the groups, the one treated with aqueous extract exhibited a absorption of glucose (16). This study showed diabetic rats larger reduction of food consumption (±56%). It is treated with aqueous extract of U. lobata produced insulin suggested that hexane and aqueous extracts of U. lobata leaf might have an initial toxic effect. Even though U. more than the ones treated with hexane or ethanolic lobata leaf ethanolic extract decreased body weight of extract of U. lobata (Fig. 1), the results lead to a suggestion diabetic rats, the extract did not affect the appetite of that water is the suitable solvent for any U. lobata diabetic rats (Table 1 and Table 2). A modification in bioactive agents concerning with insulin production. duration, frequency, and concentration of treatment may Pancreatic islet histology concerning shape and size of islet reduce the side effects observed (10). A study reported β-cells of diabetic rats received the aqueous extract of U. long-term treatment of aqueous extract of U. lobata root lobata was in conformity with its insulin production ( Fig. 1 toward New Zealand strain weaned rabbits protected the and Fig. 3). pancreas from oxidative stress (8).

anthocyanin & iso-flavonone (18). Urena lobata leaf
The studies of aqueous extract of the plant leaf in STZ extracted by petroleum ether continued with methyl induced-diabetic rats showed significant hypoglycemic alcohol result in 4 types of flavonoids, i.e. kaempferol, effects (5,7). Our study found that aqueous extract of U. quercetin, kaempferol 3-O-beta glucopyranoside, and lobata leaf at a dose of 500mg/kgBW dropped blood quercetin 3-O-rutinoside (19). A portion of ethyl acetate glucose level by 40% beneath the blood glucose level of and n-butanol of 95% ethanolic extract of branches and normal rats (Table 1 and Fig. 2); the aqueous extract of the leaf showed ten flavonoid compounds, i.e. kaempferol, leaf increased almost 5-fold the insulin serum level rutin, quercetin, afzelin, astragalin, tiliroside, kaempferolcompared with untreated diabetic rats, or the insulin 3-O-β-D-glycopyranoside-7-O-α-L-rhamnoside, increment was up to 30% insulin level in normal rats (Fig. 1  kaempferol-7-O-α-L-rhamnoside, kaempferol-7-O-α-Land Table 2); the results were accompanied with body rhamnoside-4'-O-β-D-glycopyranoside, and crenuloside weight and appetite loss (Table 1 and Table 2). The dropped (2). All flavonoids are usually water soluble and are blood glucose level might have been caused by the loss of responsible for various biological and pharmacological appetite. Metformin, GLP-1 mimetic (Exenatide), and activities in mammals, most importantly their antioxidant amylin analog (Pramlitide) are oral anti-diabetics activities (20). A study reported that markers for oxidative accompanied by body weight loss (24). The diabetic rats stress, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4received aqueous leaf extract were detected to have the hydroxy-2-nonenal (HNE)-modified protein, were lowest fasting and random blood sugar levels ( Table 1 and increased in the pancreatic β-cells of non-obese diabetic Table 2). rats (21). The present study showed morphology improvement of islet β-cells of diabetic rats, and it is Hexane extract of U. lobata leaf reduced blood glucose suggested that flavonoids of U. lobata extract play a role in level by only approximately 29% of blood glucose level in improving the condition of pancreatic islet β-cells.
diabetic rats and it was still over 40% higher than blood glucose level in normal rats (Table 2); the insulin serum The Extracts of U. lobata Leaf Corrected the Blood Glucose level was about somewhat similar with the insulin level of Level of Diabetic Rats diabetic rats treated with ethanolic extract of U. lobata leaf Hyperglycemia results in oxidative stress leading to ( Fig. 1 and Table 2); there were loss of body weight and oxidative damage of organs and increases of diabetic reduction of food consumption of the animals (Table 1 and complication risk (22). Since antioxidant enzymes are low Table 2). The study on antioxidant effects of n-hexane expressed in pancreatic islet, consequently β-cells are in a fraction of U. lobata showed no reactions (25). susceptible condition to face chronic oxidative stress due Hexane, ethanolic, and aqueous extracts of U. lobata leaf to hyperglycemia (23). Study on GK-rats (type 2 diabetic improved insulin serum level and improved the model) showed that chronic hyperglycemia might be morphology of pancreatic islet β-cells. The extracts responsible for oxidative stress in pancreatic islet β-cells corrected oral glucose tolerance tests and its area under of rats (21). Long-term treatment of aqueous extract of U.
curves. Aqueous extract of U. lobata leaf showed the best lobata leaf in the weaned rabbits followed by evaluation performance in increasing insulin and recovering islet βof oxidative status reported that SOD and catalase cells condition. The ethanolic extract showed the best activities in the serum and tissue of the rabbits were result in correcting the blood glucose level. The hexane generally higher or statistically similar to the control; the serum, liver, and pancreatic MDA levels were significantly extract of U. lobata leaf showed poor result in correcting decreased; the study showed the hypoglycemic medicinal the blood glucose level. plants did not exert oxidative damage; particularly in the pancreas, they were found to be protective against Acknowledgment oxidative damage (8).
We acknowledge the study was supported by the Ministry This study showed U. lobata leaf extracts corrected the of Research, Technology, and Higher Education of OGTTs and its AUCs. Ethanolic extract of U. lobata leaf at a I n d o n e s i a , b a s e d o n l e t t e r a g r e e m e n t N O . dose of 500mg/kgBW was optimal to correct the blood 114/B.07/U.V/LPPM/2016, May 13,2016 glucose level, it was statistically proximity with normal rats (Fig. 2). This result accompanied with insulin serum level Conflicts of Interest at 17% of the normal rats or the level was about over twofold if compared with diabetic rats (Fig. 1 and Table 2).