Tadigoppula Narender

Synthesis of novel triterpenoid (lupeol) derivatives and their in vivo antihyperglycemic and antidyslipidemic activity.

The triterpenoid, lupeol (1) has been isolated from the leaves extract of Aegle marmelos. Few novel derivatives (2-13) were synthesized from the naturally occurring lupeol (1) and screened for their antihyperglycemic activity (2-11) and antidyslipidemic activity (2-4 and 12-13). The derivative 4 lowered the blood glucose levels by 18.2% and 25.0% at 5h and 24h, respectively, in sucrose challenged streptozotocin induced diabetic rats (STZ-S) model at the dose of 100mg/kg body weight. The compound 4 also significantly lowered 40% (P <0.001) in triglycerides, 30% (P <0.05) in glycerol, 24% (P <0.05) in cholesterol quantity and also improved the HDL-cholesterol by 5% in dyslipidemic hamster model at the dose of 50mg/kg b.wt.

Peganine hydrochloride dihydrate an orally active antileishmanial agent.

Protozoic infections caused by genus Leishmania pose an enormous public health threat in developing countries, compounded by the toxicity and resistance to current therapies. Under the aegis of our ongoing program on drug discovery and development on antileishmanial agents from plants, we carried out bioassay guided fractionation on Peganum harmala seeds which resulted in the isolation of 1 as an antileishmanial agent. 2D-NMR spectral data and single crystal X-ray crystallography data indicated 1 as peganine hydrochloride in dihydrated form. The compound 1 exhibited in-vitro activity against both extracellular promastigotes as well as intracellular amastigotes residing within murine macrophages in Leishmania donovani. Furthermore, 1 also exhibited in-vivo activity, 79.6 (+/-8.07)% against established VL in hamsters at a dose of 100mg/kgb.wt.

Antihyperglycaemic effect of an unusual amino acid (4-hydroxyisoleucine) in C57BL/KsJ-db/db mice

The present report confirms the anti-hyperglycaemic and anti-dyslipidemic properties of 4-hydroxyisoleucine, an unusual amino acid isolated from Trigonella foenum-graecum seeds, for the first time in a well-characterised model of type II diabetes, i.e. db/db mice. 4-Hydroxyisoleucine, when given orally to these mice at 50 mg kg−1 dose level, significantly (p < 0.05) declined their elevated blood glucose, plasma insulin, triglycerides, total cholesterol, low-density lipoprotein-cholesterol levels and raised their declined plasma high-density lipoprotein-cholesterol level. These results indicate that 4-hydroxyisoleucine exhibits significant potential as an anti-diabetic agent by suppressing progression of type II diabetic states that is suggested by enhancement of insulin sensitivity and glucose uptake in peripheral tissue.

Anti-secretory and cyto-protective effects of chebulinic acid isolated from the fruits of Terminalia chebula on gastric ulcers.

In continuation of our drug discovery program on Indian medicinal plants, the gastro protective mechanism of chebulinic acid isolated from Terminalia chebula fruit was investigated. Chebulinic acid was evaluated against cold restraint (CRU), aspirin (AS), alcohol (AL) and pyloric ligation (PL) induced gastric ulcer models in rats. Potential anti-ulcer activity of chebulinic acid was observed against CRU (62.9%), AS (55.3%), AL (80.67%) and PL (66.63%) induced ulcer models. The reference drug omeprazole (10 mg/kg, p.o.) showed 77.73% protection against CRU, 58.30% against AS and 70.80% against PL model. Sucralfate, another reference drug (500 mg/kg, p.o.) showed 65.67% protection in AL induced ulcer model. Chebulinic acid significantly reduced free acidity (48.82%), total acidity (38.29%) and upregulated mucin secretion by 59.75% respectively. Further, chebulinic acid significantly inhibited H(+) K(+)-ATPase activity in vitro with IC50 of 65.01 μg/ml as compared to the IC50 value of omeprazole (30.24 μg/ml) confirming its anti-secretory activity.

4-Hydroxyisoleucine ameliorates fatty acid-induced insulin resistance and inflammatory response in skeletal muscle cells

The 4-hydroxyisoleucine (4-HIL), an unusual amino acid isolated from the seeds of Trigonella foenum-graecum was investigated for its metabolic effects to ameliorate free fatty acid-induced insulin resistance in skeletal muscle cells. An incubation of L6 myotubes with palmitate inhibited insulin stimulated-glucose uptake and -translocation of glucose transporter 4 (GLUT4) to the cell surface. Addition of 4-HIL strongly prevented this inhibition. We then examined the insulin signaling pathway, where 4-HIL effectively inhibited the ability of palmitate to reduce insulin-stimulated phosphorylation of insulin receptor substrate-1 (IRS-1), protein kinase B (PKB/AKT), AKT substrate of 160 kD (AS160) and glycogen synthase kinase 3β (GSK-3β) in L6 myotubes. Moreover, 4-HIL presented strong inhibition on palmitate-induced production of reactive oxygen species (ROS) and associated inflammation, as the activation of NF-κB, JNK1/2, ERK1/2 and p38 MAPK was greatly reduced. 4-HIL also inhibited inflammation-stimulated IRS-1 serine phosphorylation and restored insulin-stimulated IRS-1 tyrosine phosphorylation in the presence of palmitate, leading to enhanced insulin sensitivity. These findings suggested that 4-HIL could inhibit palmitate-induced, ROS-associated inflammation and restored insulin sensitivity through regulating IRS-1 function.

In vitro and in vivo anticancer activity of 2-deacetoxytaxinine J and synthesis of novel taxoids and their in vitro anticancer activity

The taxane diterpneoid 2-deacetoxytaxinine J (2-DAT-J) 1 has been isolated from the bark of Himalayan yew, Taxus baccata L. spp. wallichiana in a reasonably good yield (0.1%) and its anticancer activity against breast cancer cell lines (MCF-7 and MDA-MB-231) and normal human kidney epithelial cell line (HEK-293) has been studied. 2-DAT-J (1) showed significant in vitro activity against breast cancer cell line at a concentration of 20 microM and 10 microM in MCF-7 and MDA-MB-231 respectively. Few novel taxoids were derived (7, 8 and 10-13) from the naturally occurring 2-DAT-J (1) and screened for their anticancer activity. The structure-activity relationship studies indicated that the cinnamoyl group on C-5 and acetyl group on C-10 are essential for the anticancer activity. 2-DAT-J (1) was also tested for its in vivo activity on DMBA-induced mammary tumors in virgin female Sprague Dawley rats at a dose of 10mg/kg body weight orally for 30 days and showed significant regression in mammary tumors as compared to vehicle treated group (p<0.05).

Silver(I)-Catalyzed Regioselective Construction of Highly Substituted α-Naphthols and Its Application toward Expeditious Synthesis of Lignan Natural Products

A novel route has been developed for regioselective synthesis of highly substituted α-naphthols, binaphthols, and anthracenol through silver(I) catalyzed C(sp(3))-H/C(sp)-H, C(sp(2))-H/C(sp)-H functionalization of β-ketoesters and alkynes, respectively, in a single step using water as a solvent. This protocol exhibited broad substrate scope and paved the way for synthesis of anticancer arylnaphthalene lignan natural products such as diphyllin, taiwanin E, and justicidin A with excellent selectivity.

Antidyslipidemic and antioxidant activity of the constituents isolated from the leaves of Calophyllum inophyllum.

In continuation of our drug discovery program on Indian medicinal plants, we isolated bioactive compounds (1-5) from the leaves of Calophyllum inophyllum and evaluated their antidyslipidemic activity in triton induced hyperlipidemia model. The calophyllic acid (1A) and isocalophyllic acid (1B) mixture, canophyllic acid (4) and amentoflavone (5) showed dose dependent lipid lowering activity in in vivo experiments. The compounds 1A+1B mixture and 3 also showed good in vitro antioxidant activity.

Preliminary studies on the hypoglycemic effect of Peganum harmala L. Seeds ethanol extract on normal and streptozotocin induced diabetic rats

Peganum harmala L. (Zygophyllaceae) is a traditional medicine used for the treatment of variety of human ailments, including antidepression, hallucination, antileishmaniasis etc. We report for first time the hypoglycemic activity of the ethanolic extract of this plant at two dose levels of 150 and 250mg/kg bw in sucrose challenged normal as well as in rats with streptozotocin induced diabetes. The oral administration of ethanolic extract causes maximum fall of blood glucose level to 22.9% (p<0.05) and 29.4% (p<0.01) respectively with the two doses in normal and 30.3% (p<0.01) and 48.4% (p<0.001) in diabetic rats. The standard drug metformin treated group showed 28.0% (p<0.01) and 45.5% (p<0.001) respectively in normal and diabetic rats. The above results show that the ethanolic extract of P. harmala is as effective as metformin in reducing the blood glucose levels of normoglycemic and streptozotocin-induced diabetic rats.

Synthesis of novel triterpene and N-allylated/N-alkylated niacin hybrids as α-glucosidase inhibitors

Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia. α-Glucosidase (EC 3.2.1.20) inhibitors interfere with enzymatic action to slow down the liberation of d-glucose from oligosaccharides and disaccharides, resulting in delayed glucose absorption and decreased postprandial plasma glucose levels. In continuation of our drug discovery program on antidiabetic agents, we synthesized novel N-allylated/N-alkylated niacin and α-amyrin (4-9) and lupeol (12-16) hybrids and tested for their α-glucosidase inhibiting activity. Compounds 4-9 showed better activity profile than the marketed α-glucosidase inhibitor i.e. acarbose. Compound 4 possess the highest inhibitory action with IC50 of 5 μM. Kinetic and CD studies revealed that 4 inhibited the α-glucosidase in a noncompetitive manner and caused conformational changes in secondary structure of the enzyme protein.