K. Balakrishna

Petroleum and polycyclic aromatic hydrocarbons (PAHs) degradation and naphthalene metabolism in Streptomyces sp. (ERI-CPDA-1) isolated from oil contaminated soil.

Petroleum and polycyclic aromatic hydrocarbons (PAHs) degrading Streptomyces sp. isolate ERI-CPDA-1 was recovered from oil contaminated soil in Chennai, India. The degradation efficiencies were examined by GC-FID and the results showed that the isolate could remove 98.25% diesel oil, 99.14% naphthalene and 17.5% phenanthrene in 7 days at 30°C (0.1%). ERI-CPDA-1 was able to degrade naphthalene, phenanthrene and diesel oil and grow on petrol, diesel, kerosene, benzene, pyridine, methanol, ethanol, cyclohexane, tween-80, xylene, DMSO and toluene using them as sole carbon source. Effects of environmental condition on degradation of hydrocarbons (diesel oil, naphthalene and phenanthrene) were also studied at different pH, NaCl, temperature, concentration and incubation time. Degradation pathway for naphthalene has been proposed. Degradation metabolites were identified using GC-MS analysis of ethyl acetate extract of the cell free culture. The degradation products detected were benzaldehyde, catechol, phenylacetic acid and protocatechuic acid.

Insulin sensitization via partial agonism of PPARγ and glucose uptake through translocation and activation of GLUT4 in PI3K/p-Akt signaling pathway by embelin in type 2 diabetic rats.

BACKGROUND The present study was aimed at isolating an antidiabetic molecule from a herbal source and assessing its mechanism of action. METHODS Embelin, isolated from Embelia ribes Burm. (Myrsinaceae) fruit, was evaluated for its potential to regulate insulin resistance, alter β-cell dysfunction and modulate key markers involved in insulin sensitivity and glucose transport using high-fat diet (HFD) fed-streptozotocin (STZ) (40mg/kg)-induced type 2 diabetic rats. Molecular-dockings were performed to investigate the binding modes of embelin into PPARγ, PI3K, p-Akt and GLUT4 active sites. RESULTS Embelin (50mg/kg b wt.) reduced body weight gain, blood glucose and plasma insulin in treated diabetic rats. It further modulated the altered lipid profiles and antioxidant enzymes with cytoprotective action on β-cell. Embelin significantly increased the PPARγ expression in epididymal adipose tissue compared to diabetic control group; it also inhibited adipogenic activity; it mildly activated PPARγ levels in the liver and skeletal muscle. It also regulated insulin mediated glucose uptake in epididymal adipose tissue through translocation and activation of GLUT4 in PI3K/p-Akt signaling cascade. Embelin bound to PPARγ; it disclosed stable binding affinities to the active sites of PI3K, p-Akt and GLUT4. CONCLUSIONS These findings show that embelin could improve adipose tissue insulin sensitivity without increasing weight gain, enhance glycemic control, protect β-cell from damage and maintain glucose homeostasis in adipose tissue. GENERAL SIGNIFICANCE Embelin can be used in the prevention and treatment of type 2 diabetes mellitus caused due to obesity.

Gallic acid attenuates high-fat diet fed-streptozotocin-induced insulin resistance via partial agonism of PPARγ in experimental type 2 diabetic rats and enhances glucose uptake through translocation and activation of GLUT4 in PI3K/p-Akt signaling pathway

In this study, the therapeutic efficacy of gallic acid from Cyamopsis tetragonoloba (L.) Taub. (Fabaceae) beans was examined against high-fat diet fed-streptozotocin-induced experimental type 2 diabetic rats. Molecular-dockings were done to determine the putative binding modes of gallic acid into the active sites of key insulin-signaling markers. Gallic acid (20 mg/kg) given to high-fat diet fed-streptozotocin-induced rats lowered body weight gain, fasting blood glucose and plasma insulin in diabetic rats. It further restored the alterations of biochemical parameters to near normal levels in diabetic treated rats along with cytoprotective action on pancreatic β-cell. Histology of liver and adipose tissues supported the biochemical findings. Gallic acid significantly enhanced the level of peroxisome proliferator-activated receptor γ (PPARγ) expression in the adipose tissue of treated rat compared to untreated diabetic rat; it also slightly activated PPARγ expressions in the liver and skeletal muscle. Consequently, it improved insulin-dependent glucose transport in adipose tissue through translocation and activation of glucose transporter protein 4 (GLUT4) in phosphatidylinositol 3-kinase (PI3K)/phosphorylated protein kinase B (p-Akt) dependent pathway. Gallic acid docked with PPARγ; it exhibited promising interactions with the GLUT4, glucose transporter protein 1 (GLUT1), PI3K and p-Akt. These findings provided evidence to show that gallic acid could improve adipose tissue insulin sensitivity, modulate adipogenesis, increase adipose glucose uptake and protect β-cells from impairment. Hence it can be used in the management of obesity-associated type 2 diabetes mellitus.

Effect of niloticin, a protolimonoid isolated from Limonia acidissima L. (Rutaceae) on the immature stages of dengue vector Aedes aegypti L. (Diptera: Culicidae).

The aim of the present study was to evaluate the mosquitocidal activity of fractions and a compound niloticin from the hexane extract of Limonia acidissima L. leaves on eggs, larvae and pupae of Aedes aegypti L. (Diptera: Culicidae). In these bioassays, the eggs, larvae and pupae were exposed to concentrations of 2.5, 5.0, 7.5 and 10.0ppm for fractions and 0.5, 1.0, 1.5 and 2.0ppm for compound. After 24h, the mortality was assessed and the LC50 and LC90 values were calculated for larvae and pupae. Per cent ovicidal activity was calculated for eggs after 120h post treatment. Among the sixteen fractions screened, fraction 8 from the hexane extract of L. acidissima generated good mosquitocidal activity against Ae. aegypti. The LC50 and LC90 values of fraction 8 were 4.11, 8.04ppm against Ae. aegypti larvae and 4.19, 8.10ppm against Ae. aegypti pupae, respectively. Further, the isolated compound, niloticin recorded strong larvicidal and pupicidal activities. The 2ppm concentration of niloticin showed 100% larvicidal and pupicidal activities in 24h. The LC50 and LC90 values of niloticin on Ae. aegypti larvae were 0.44, 1.17ppm and on pupae were 0.62, 1.45ppm, respectively. Niloticin presented 83.2% ovicidal activity at 2ppm concentration after 120h post treatment and niloticin exhibited significant growth disruption and morphological deformities at sub lethal concentrations against Ae. aegypti. The structure of the isolated compound was identified on the basis of single XRD and spectral data ((1)H NMR and (13)C NMR) and compared with literature spectral data. The results indicate that niloticin could be used as a potential natural mosquitocide.

Hypoglycemic activity of 6-bromoembelin and vilangin in high-fat diet fed-streptozotocin-induced type 2 diabetic rats and molecular docking studies.

AIMS This paper investigates the hypoglycemic activity of two derivatives of embelin (1) viz. 6-bromoembelin (2) and vilangin (3), in high-fat diet - STZ induced diabetic rats. MAIN METHODS The effects of 6-bromoembelin (2) and vilangin (3) on insulin resistance, β-cell dysfunction and glucose transport in high-fat diet (HFD) fed-streptozotocin (STZ) (40mg/kg) induced type 2 diabetic rats were evaluated. The binding modes of 6-bromoembelin (2) and vilangin (3) into PPARγ, PI3K, Akt, and GLUT4 were also studied using Autodock 4.2 and ADT 1.5.6 programs. KEY FINDINGS At the dose of 30mg/kg, the plasma glucose, plasma insulin and body weight were reduced by both embelin derivatives in diabetic rats. Additionally the altered lipid profiles and hexokinase, glucose-6-phosphatase and fructose-1,6-bisphosphatase levels were brought to normal. Compared to diabetic control group, there was a significant increase in the expression of PPARγ in epididymal adipose tissue. Inhibition of adipogenic activity and mild activation of PPARγ levels in the skeletal muscle and liver were observed. In epididymal adipose tissue, the compounds increased the insulin-mediated glucose uptake through the activation and translocation of GLUT4 in PI3K/p-Akt signaling cascade. SIGNIFICANCE The derivatives of embelin such as 6-bromoembelin (2) and vilangin (3) may be useful in the prevention and treatment of obesity-linked type 2 diabetes mellitus.

Myoinositol ameliorates high-fat diet and streptozotocin-induced diabetes in rats through promoting insulin receptor signaling

Mimosa pudica Linn. (Mimosaceae) has been traditionally used for the management of type 2 diabetes mellitus (T2DM) in India. The present study evaluates the therapeutic efficacy of myoinositol (25 and 50mg/kg) isolated from M. pudica stem methanol extract in Triton WR-1339 induced hyperlipidemic and high-fat diet (HFD) fed-streptozotocin (STZ)-induced insulin-resistant diabetic rats. Lipid biomarkers, fasting blood glucose (FBG), changes in body weight, food and water intakes, plasma insulin, HOMA-IR, oral glucose tolerance, intraperitoneal insulin tolerance, urea, creatinine, marker enzymes of liver function, β-cell function and the expression levels of insulin receptor-induced signaling molecules were studied. Molecular-docking was also carried out to determine the possible interactions of myoinositol into the active sites of insulin-induced signaling markers. In addition, histology of liver, pancreas, kidney, heart and adipose tissues were also performed. In Triton WR-1339 induced hyperlipidemic rats, myoinositol (25 and 50mg/kg) exhibited significant reductions in total cholesterol: 37.5% and 59.73%, triglycerides: 57.75% and 80.14% and LDL-c: 81.44% and 101.75% respectively. HFD fed-STZ receiving myoinositol (25 and 50mg/kg) showed significant reductions in fasting blood glucose: 55.68% and 56.48%, plasma insulin level: 25.45% and 27.06% when compared with diabetic control. It significantly normalized the hyperglycemia induced biochemical abnormalities in insulin-resistant diabetic rats. Furthermore, it demonstrated cytoprotective effects besides increase in the intensity of positive reaction for insulin in pancreas. Myoinositol enhanced the level of PPARγ expression in the adipose tissue of treated rats when compared with rats that did not receive drug treatment; also, it significantly upregulated GLUT4 and IR signaling molecules. Myoinositol had predicted the interactions within the active sites of PPARγ, GLUT4 and IR. These findings suggested that myoinositol could play an effective role in glucose disposal into adipose tissue by insulin-dependent signaling cascade mechanism; hence it could be used in the treatment of obesity-associated T2DM.

Effect of two andrographolide derivatives on cellular and rodent models of non-alcoholic fatty liver disease

The prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD) is increasing and there is an increasing interest in natural products to treat NAFLD. This study aimed to evaluate the hepatoprotective effect of andrographolide and two of its derivatives; in one the OH group at C-14 was removed and in the other OH groups at C-3 and C-19 were protected. Andrographolide (AN) was isolated from the aerial parts of Andrographis paniculata Wall. Isoandrographolide (IAN) and 3,19-acetonylidene andrographolide (ANA) were derivatized from AN. Drug likeness of the compounds was studied using DataWarrior. The effect of the compounds in ameliorating hepatic steatosis and lipotoxicity was assessed using palmitate-oleate induced steatotic HepG2 cell lines. In vivo efficacy of the compounds was assessed by using HFD fed rats. IAN showed comparatively high drug score and low irritability than AN. MTT assay indicated that the treatment with IAN had comparatively less toxicity than AN and ANA to HepG2 cells. The treatment with IAN significantly reduced the lipid accumulation and the leakage of LDH and transaminases, while the treatments with AN and ANA did not prohibit the leakage. In the in vivo experiment, the treatment with IAN showed comparatively better hepatoprotection by reducing the serum lipid, transaminases and ALP levels than with AN and ANA. Our results showed that IAN could be a promising lead to treat NAFLD with comparatively low toxicity and improved efficacy.

Bioefficacy of ecbolin A and ecbolin B isolated from Ecbolium viride (Forsk.) Alston on dengue vector Aedes aegypti L. (Diptera: Culicidae)

Ecbolin A and ecbolin B were isolated from ethyl acetate extract of Ecbolium viride (Forsk.) Alston root and evaluated for larvicidal and growth disturbance activities against Aedes aegypti L. (Diptera: Culicidae). For larvicidal activity, the third instar larvae of A. aegypti were exposed to different concentrations viz., 1.0, 2.5, 5.0 and 10 ppm for each compound. Among the two compounds screened, ecbolin B recorded highest larvicidal activity with LC50 and LC90 values of 0.70 and 1.42 ppm, respectively. In control, the larval behaviour was normal. The active compound ecbolin B was tested for growth disruption activity at sub lethal concentrations viz., 0.5, 1.0 ppm and observed for malformation like larval gut elongation, larval longevity, intermediates, malformed adults, failed adult emergence and compared with methoprene. The results showed significant level of larva–pupa intermediates, pupa–adult intermediates, malformed adult emergence and less adult formation against A. aegypti. The histopathological results revealed a severe damage on the midgut epithelial columnar cells (CC) and cuboidal cells (CU) in ecbolin B treated larvae of A. aegypti. Similarly peritrophic membrane (pM) was also observed to be damaged in the treated larvae. The present results suggest that, ecbolin B could be used as a larvicidal agent against dengue vector A. aegypti.

Hepatoprotective effect of lawsone on rifampicin-isoniazid induced hepatotoxicity in in vitro and in vivo models

The Drug-induced liver injury is one of the common unfavourable impacts, which seriously affects any drug therapy. This study documented the hepatoprotective efficacy of lawsone, the major bioactive naphthoquinone present in Lawsonia inermis L. (Lythraceae) using in vitro and in vivo models. Lawsone was isolated from the leaves of L. inermis and its structure was confirmed using spectroscopic data. In-vitro antioxidant effect of lawsone was evaluated using ABTS assay. Hepatoprotective effect of lawsone was determined with RIF-INH treated HepG2 cells and Wistar rats. Administration of RIF-INH reduced the viability of the HepG2 cells and the treatment with lawsone significantly restored the viability of the cells even at lower concentration (7.5 μM). The other parameters such as the leakage of transaminases and MDA levels were also significantly reduced by the treatment with lawsone. Oral administration of lawsone to the animals did not show any toxicity up to 2 g/kg b.w. concentration. Treatment with lawsone to the RIF-INH administered animals significantly lowered the serum transaminases levels. The ratio of albumin to globulin was improved and the level of bilirubin was lowered. This study indicated the hepatoprotective effect of lawsone; detailed investigations will give deeper understanding of the application of lawsone for hepatoprotection.

Bioassay guided fractionation and identification of active anti-inflammatory constituent from Delonix elata flowers using RAW 264.7 cells.

Abstract Context: Delonix elata (L.) Gamble (Fabaceae) has been used in the Indian traditional medicine system to treat rheumatism and inflammation. Aim: To assess the anti-inflammatory effect of Delonix elata flowers and to isolate the active principle. Materials and methods: The prompt anti-inflammatory constituent was isolated from Delonix elata flower extracts using bioassay guided fractionation in liposaccharide (LPS) stimulated RAW 264.7 macrophage cell line. The anti-inflammatory activity of extracts/fractions/sub-fractions/compounds (10, 25, and 50 µg/ml) was evaluated by estimating the levels of nitric oxide (NO), TNF-α, and IL-1β after 24 h of LPS induction (1 μg/ml). The isolated active compound was subjected to NMR, IR, and UV analyses for structure determination. Results: In an attempt to search for anti-inflammatory constituents, the active pure principle was isolated and crystallized as a white compound from Delonix elata flowers methanol extract. This active compound (50 µg/ml) decreased the release of inflammatory mediators levels such as NO (0.263 ± 0.03 µM), TNFα (160.20 ± 17.57 pg/ml), and IL-1β (285.79 ± 15.16 pg/ml) significantly (p < 0.05); when compared to the levels of NO (0.774 ± 0.08 µM), TNFα (501.71 ± 25.14 pg/ml), and IL-1β (712.68 ± 52.25 pg/ml) from LPS-stimulated macrophage cells. The active compound was confirmed as hesperidin with NMR, IR, and UV spectroscopy data. This is the first report of this compound from Delonix elata flowers. Conclusion: The findings of the study support the traditional use of Delonix elata flowers to treat inflammation.