Bimba N. Joshi

Antidiabetic Indian Plants: A Good Source of Potent Amylase Inhibitors

Diabetes is known as a multifactorial disease. The treatment of diabetes (Type II) is complicated due to the inherent patho-physiological factors related to this disease. One of the complications of diabetes is post-prandial hyperglycemia (PPHG). Glucosidase inhibitors, particularly α-amylase inhibitors are a class of compounds that helps in managing PPHG. Six ethno-botanically known plants having antidiabetic property namely, Azadirachta indica Adr. Juss.; Murraya koenigii (L.) Sprengel; Ocimum tenuflorum (L.) (syn: Sanctum); Syzygium cumini (L.) Skeels (syn: Eugenia jambolana); Linum usitatissimum (L.) and Bougainvillea spectabilis were tested for their ability to inhibit glucosidase activity. The chloroform, methanol and aqueous extracts were prepared sequentially from either leaves or seeds of these plants. It was observed that the chloroform extract of O. tenuflorum; B. spectabilis; M. koenigii and S. cumini have significant α-amylase inhibitory property. Plants extracts were further tested against murine pancreatic, liver and small intestinal crude enzyme preparations for glucosidase inhibitory activity. The three extracts of O. tenuflorum and chloroform extract of M. koenigi showed good inhibition of murine pancreatic and intestinal glucosidases as compared with acarbose, a known glucosidase inhibitor.

Antidiabetic Activity of Gnidia glauca and Dioscorea bulbifera: Potent Amylase and Glucosidase Inhibitors

Diabetes is a metabolic disorder affecting about 220 million people worldwide. One of the most critical complications of diabetes is post-prandial hyper-glycemia (PPHG). Glucosidase inhibitor and α-amylase inhibitors are class of compounds that help in managing PPHG. Low-cost herbal treatment is recommended due to their lesser side effect for treatment of diabetes. Two plants with significant traditional therapeutic potential, namely, Gnidia glauca and Dioscorea bulbifera, were tested for their efficiency to inhibit α-amylase and α-glucosidase. Stem, leaf, and flower of G. glauca and bulb of D. bulbifera were sequentially extracted with petroleum ether, ethyl acetate, and methanol as well as separately with 70% ethanol. Petroleum ether extract of flower of G. glauca was found to inhibit α-amylase significantly (78.56%). Extracts were further tested against crude murine pancreatic, small intestinal, and liver glucosidase enzyme which revealed excellent inhibitory properties. α-glucosidase inhibition provided a strong in vitro evidence for confirmation of both G. glauca and D. bulbifera as excellent antidiabetic remedy. This is the first report of its kind that provides a strong biochemical basis for management of type II diabetes using G. glauca and D. bulbifera. These results provide intense rationale for further in vivo and clinical study.

Antidiabetic Properties of Azardiracta indica and Bougainvillea spectabilis: In Vivo Studies in Murine Diabetes Model

Diabetes mellitus is a metabolic syndrome characterized by an increase in the blood glucose level. Treatment of diabetes is complicated due to multifactorial nature of the disease. Azadirachta indica Adr. Juss and Bougainvillea spectabilis are reported to have medicinal values including antidiabetic properties. In the present study using invivo diabetic murine model, A. indica and B. spectabilis chloroform, methanolic and aqueous extracts were investigated for the biochemical parameters important for controlling diabetes. It was found that A. indica chloroform extract and B. spectabilis aqueous, methanolic extracts showed a good oral glucose tolerance and significantly reduced the intestinal glucosidase activity. Interestingly, A. indica chloroform and B. spectabilis aqueous extracts showed significant increase in glucose-6-phosphate dehydrogenase activity and hepatic, skeletal muscle glycogen content after 21 days of treatment. In immunohistochemical analysis, we observed a regeneration of insulin-producing cells and corresponding increase in the plasma insulin and c-peptide levels with the treatment of A. indica chloroform and B. spectabilis aqueous, methanolic extracts. Analyzing the results, it is clear that A. indica chloroform and B. spectabilis aqueous extracts are good candidates for developing new neutraceuticals treatment for diabetes.

Highly Stable Hexacoordinated Nonoxidovanadium(IV) Complexes of Sterically Constrained Ligands: Syntheses, Structure, and Study of Antiproliferative and Insulin Mimetic Activity

Three highly stable, hexacoordinated nonoxidovanadium(IV), V(IV)(L)2, complexes (1-3) have been isolated and structurally characterized with tridentate aroylhydrazonates containing ONO donor atoms. All the complexes are stable in the open air in the solid state as well as in solution, a phenomenon rarely observed in nonoxidovanadium(IV) complexes. The complexes have good solubility in organic solvents, permitting electrochemical and various spectroscopic investigations. The existence of nonoxidovanadium(IV) complexes was confirmed by elemental analysis, ESI mass spectroscopy, cyclic voltammetry, EPR, and magnetic susceptibility measurements. X-ray crystallography showed the N3O3 donor set to define a trigonal prismatic geometry in each case. All the complexes show in vitro insulin mimetic activity against insulin responsive L6 myoblast cells, with complex 3 being the most potent, which is comparable to insulin at the complex concentration of 4 μM, while the others have moderate insulin mimetic activity. In addition, the in vitro antiproliferative activity of complexes 1-3 against the HeLa cell line was assayed. The cytotoxicity of the complexes is affected by the various functional groups attached to the bezoylhydrazone derivative and 2 showed considerable antiproliferative activity compared to the most commonly used chemotherapeutic drugs.

Ruthenium(II) polypyridyl complex as inhibitor of acetylcholinesterase and Aβ aggregation

Two ruthenium(II) polypyridyl complexes [Ru(phen)3](2+) (1) and [Ru(phen)2(bxbg)](2+) (2) (where phen = 1,10 phenanthroline, bxbg = bis(o-xylene)bipyridine glycoluril) have been evaluated for acetylcholinesterase (AChE) and Amyloid-β peptide (Aβ) aggregation inhibition. Complex 2 exhibits higher potency of AChE inhibition and kinetics and molecular modeling studies indicate that ancillary ligand plays significant role in inhibitory potency exhibited by complex 2. The inhibitory effect of these complexes on Aβ (1-40) aggregation is investigated using Thioflavin T fluorescence and Transmission Electron Microscopy. Both complexes efficiently inhibit Aβ (1-40) aggregation and are negligibly toxic to human neuroblastoma cells. This is the first demonstration that ruthenium(II) polypyridyl complexes simultaneously inhibit AChE and Aβ aggregation.

Thiosemicarbazone modification of 3-acetyl coumarin inhibits Aβ peptide aggregation and protect against Aβ-induced cytotoxicity

Aggregation of amyloid β peptide (Aβ) is an important event in the progression of Alzheimers disease. Therefore, among the available therapeutic approaches to fight with disease, inhibition of Aβ aggregation is widely studied and one of the promising approach for the development of treatments for Alzheimers disease. Thiosemicarbazone compounds are known for their variety of biological activities. However, the potential of thiosemicarbazone compounds towards inhibition of Aβ peptide aggregation and the subsequent toxicity is little explored. Herein, we report synthesis and x-ray crystal structure of novel compound 3-acetyl coumarin thiosemicarbazone and its efficacy toward inhibition of Aβ(1-42) peptide aggregation. Our results indicate that 3-acetyl coumarin thiosemicarbazone inhibits Aβ(1-42) peptide aggregation up to 80% compared to the parent 3-acetyl coumarin which inhibits 52%. Further, 3-acetyl coumarin thiosemicarbazone provides neuroprotection against Aβ-induced cytotoxicity in SH-SY5Y cell line. These findings indicate that thiosemicarbazone modification renders 3-acetyl coumarin neuroprotective properties.

Orally active hypoglycemic protein from Costus igneus N. E. Br.: an in vitro and in vivo study.

Plants have been used for the treatment of diabetes since time immemorial. In the present study, insulin-like protein (ILP) is purified from Costus igneus belonging to family Costaceae from Western ghats of India. The ILP showed cross reactivity with murine anti-insulin antibodies hence was purified by affinity chromatography using anti-insulin antibodies. The characterization of ILP showed that it is structurally different from insulin but functionally similar. The ILP showed a hypoglycemic activity in an in vitro assay with insulin responsive cell line RIN 5f. Interestingly ILP showed significant decrease in blood glucose level when administered orally in oral glucose tolerance test. This was compared to insulin a positive control given intraperitoneally in streptozotocine induced diabetic mice. There was no toxic effect seen on animals after administrating the ILP. Therefore we conclude that the ILP purified in the present study from C. igneus is a novel protein having hypoglycemic activity.

Beneficial effect of flax seeds in streptozotocin (STZ) induced diabetic mice: isolation of active fraction having islet regenerative and glucosidase inhibitory properties

Diabetes mellitus is a metabolic disorder that affects millions of people worldwide. Present study highlights the antidiabetogenic property of Linum usitassimum active fraction (LU6) in streptozotocin (STZ) induced diabetic Swiss mice. Treatment with LU6 fraction showed improved glucose utilization with increase in liver glucose-6-phosphate dehydrogenase enzyme activity and normal glycogenesis in hepatic and muscle tissues. Reduction in pancreatic and intestinal glucosidase inhibitory activity was observed with LU6 treatment, indicating beneficial effects in reducing postprandial hyperglycemia (PPHG). Normalization of plasma insulin and C-peptide levels were observed in diabetic mice, indicating endogenous insulin secretion after the treatment with LU6. The histochemical and immunohistochemical analysis on pancreatic islets suggests the role of LU6 fraction in islet regeneration and insulin secretion as evident in increase functional pancreatic islets producing insulin. Furthermore, significant insulin producing islet formation was also observed in in vitro PANC-1 cells after LU6 treatment, indicating the cellular aggregates to be newly formed islets. This suggests the potential of LU6 fraction in the formation of new islets in vitro, as well as in vivo. Thus, LU6 can be used as a neutraceutical-based first-line treatment for diabetes.

Effects of oxidation on copper-binding properties of Aβ1-16 peptide: A pulse radiolysis study

Abstract The reaction of hydroxyl radicals (•OH) with Aβ1-16 peptide was carried out using pulse radiolysis to understand the effect of oxidation of peptide on its copper-binding properties. This reaction produced oxidized, dimeric and trimeric Aβ1-16 peptide species. The formation of these products was established with the help of fluorescence spectroscopy and mass spectrometry. The mass spectral data indicate that the major site of oxidation is at His6, while the site for dimerization is at Tyr10. Diethyl pyrocarbonate-treated Aβ1-16 peptide did not produce any trimeric species upon oxidation with •OH. The quantitative chemical modification studies indicated that one of the three histidine residues is covalently modified during pulse radiolysis. The copper-binding studies of the oxidized peptide revealed that it has similar copper-binding properties as the unoxidized peptide. Further, the cytotoxicity studies point out that both oxidized and unoxidized Aβ1-16 peptide are equally efficient in producing free radicals in presence of copper and ascorbate that resulted in comparable cell death.

Effects of oxidation on redox and cytotoxic properties of copper complex of Aβ1–16 peptide

Abstract The effect of oxidation on redox and cytotoxic properties of copper complex of amyloid beta (Aβ) peptide was studied by gamma radiolysis. The oxidation of Aβ1–16 and Aβ1–16/Cu(II) complex was carried out using hydroxyl (•OH) radicals produced by gamma radiolysis and the products were analyzed using mass spectrometry. The presence of Cu(II) was found to enhance the oxidation of Aβ1–16 peptide. The oxidation of residues Asp1, His6, and His13 was enhanced due to their involvement in copper binding. The oxidation of His residues of Aβ1–16 peptide, which are chiefly responsible for copper binding, resulted in altered redox properties and subsequently in higher cytotoxicity of the Aβ1–16 peptide in SH-SY5Y cells.