Narender Tadigoppula

Synthesis and insight into the structure-activity relationships of chalcones as antimalarial agents.

Licochalcone A (I), isolated from the roots of Chinese licorice, is the most promising antimalarial compound reported so far. In continuation of our drug discovery program, we isolated two similar chalcones, medicagenin (II) and munchiwarin (III), from Crotalaria medicagenia , which exhibited antimalarial activity against Plasmodium falciparum . A library of 88 chalcones were synthesized and evaluated for their in vitro antimalarial activity. Among these, 67, 68, 74, 77, and 78 exhibited good in vitro antimalarial activity against P. falciparum strains 3D7 and K1 with low cytotoxicity. These chalcones also showed reduction in parasitemia and increased survival time of Swiss mice infected with Plasmodium yoelii (strain N-67). Pharmacokinetic studies indicated that low oral bioavailability due to poor ADME properties. Molecular docking studies revealed the binding orientation of these inhibitors in active sites of falcipain-2 (FP-2) enzyme. Compounds 67, 68, and 78 showed modest inhibitory activity against the major hemoglobin degrading cysteine protease FP-2.

Synthesis, structure-activity relationships, and biological studies of chromenochalcones as potential antileishmanial agents.

Antileishmanial activities of a library of synthetic chalcone analogues have been examined. Among them, five compounds (11, 14, 16, 17, 22, and 24) exhibited better activity than the marketed drug miltefosine in in vitro studies against the intracellular amastigotes form of Leishmania donovani. Three promising compounds, 16, 17, and 22, were tested in a L. donovani/hamster model. Oral administration of chalcone 16, at a concentration of 100 mg/kg of body weight per day for 5 consecutive days, resulted in >84% parasite inhibition at day 7 post-treatment and it retained the activity until day 28. The molecular and immunological studies revealed that compound 16 has a dual nature to act as a direct parasite killing agent and as a host immunostimulant. Pharmacokinetics and serum albumin binding studies also suggest that compound 16 has the potential to be a candidate for the treatment of the nonhealing form of leishmaniasis.

Synthesis of new andrographolide derivatives and evaluation of their antidyslipidemic, LDL-oxidation and antioxidant activity

Andrographis paniculata, native to Taiwan, Mainland China and India, is a medicinal herb, which possesses various biological activities including anti-atherosclerosis. Andrographolide (1) has been identified as one of the active constituents against atherosclerosis. In continuation of our drug discovery program we synthesized few novel derivatives of 1 to improve their antidyslipidemic, LDL-oxidation and antioxidant activity. The tosylated derivative 7 has been turned out to be more potent than the parent compound and comparable activity with marketed antidyslipidemic drugs.

PhI(OAc)2–BF3–OEt2 mediated domino imine activation, intramolecular C–C bond formation and β-elimination: new approach for the synthesis of fluorenones, xanthones and phenanthridines

PhI(OAc)2–BF3–OEt2 mediated domino synthesis of biologically important fluorenones, xanthones and phenanthridines has been developed. The reaction proceeds through imine activation, intramolecular C–C bond formation and β-elimination.

Curcumin-3,4-Dichloro Phenyl Pyrazole (CDPP) overcomes curcumin's low bioavailability, inhibits adipogenesis and ameliorates dyslipidemia by activating reverse cholesterol transport

BACKGROUND Adipocyte dysfunction, obesity and associated metabolic disorders are of prime healthcare concern worldwide. Among available medications, natural products and inspired molecules hold 40% space in clinically prescribed medicines. In queue, this study overcomes the drawback of curcumins low bioavailability with potent anti-adipogenic and anti-dyslipidemic activity. METHODS To evaluate the role of CDPP on adipocyte differentiation, 3T3-L1 adipocytes were used as an in-vitro model. Flow cytometry was performed for cell cycle analysis. Syrian golden hamsters were used to study pharmacokinetic profile and dyslipidemic activity exhibited by CDPP. RESULT CDPP was found to be a potent inhibitor of adipogenesis in-vitro. It blocked mitotic clonal expansion by causing cell cycle arrest. CDPP showed marked improvement in gastrointestinal stability and bioavailability in-vivo as compared to curcumin. Administration of CDPP (100mg/kg) significantly improved HFD induced dyslipidemic profile in hamsters and activated reverse cholesterol transport machinery. CONCLUSION CDPP could be used as a potential drug candidate against adipogenesis and dyslipidemia with enhanced gastrointestinal stability and bioavailability.

4-Hydroxyisoleucine improves insulin resistance by promoting mitochondrial biogenesis and act through AMPK and Akt dependent pathway.

4-Hydroxyisoleucine (4-HIL) is an unusual amino acid isolated from fenugreek seeds (Trigonella foenum graecum L). Various studies have shown that it acts as an antidiabetic agent yet its mechanism of action is not clear. We therefore investigated the effect 4-HIL on the high fructose diet fed streptozotocin induced diabetic rats and L6 myotubes. 4-HIL (50 mg/kg) has improved blood lipid profile, glucose tolerance and insulin sensitivity in a diabetic rat model. It has increased the glucose uptake in L6 myotubes in AMPK-dependent manner and upregulated the expression of genes (PGC-1α, PGC-1β, CPT 1 and CPT 2), which have role in mitochondrial biogenesis and energy metabolism in the liver, skeletal muscles as well as in L6 myotubes. Interestingly, it also increased the AMPK and Akt expression along with their phosphorylated forms in the liver and muscle tissues of treated animals. Altogether we concluded that 4-HIL acts to improve insulin resistance by promoting mitochondrial biogenesis in high fructose diet fed STZ induced diabetic rats.

Synthesis of new N-acryl-1-amino-2-phenylethanol and N-acyl-1-amino-3-aryloxypropanols and evaluation of their antihyperlipidemic, LDL-oxidation and antioxidant activity.

As a part of our drug discovery program, we identified an alkaloidal amide i.e. Aegeline (V) isolated from the leaves of Aegle marmelos as a dual acting agent (antihyperlipidemic and antihyperglycemic). In continuation of this program, we synthesized new N-acyl-1-amino-2-alcohols (N-acrylated-1-amino-2-phenylethanol and N-acylated-1-amino-3-aryloxypropanols) via Ritter reaction and screened for their in-vivo antihyperlipdemic activity in Triton induced hyperlipidemia model, LDL-oxidation and antioxidant activity. Compounds 3, 11 and 13 showed good antihyperlipidemic activity, LDL-oxidation as well as antioxidant activity and comparable activity with marketed antidyslipidemic drug.

Synthesis of novel anticancer iridoid derivatives and their cell cycle arrest and caspase dependent apoptosis.

Nyctanthes arbortristis Linn (Oleaceae) is widely distributed in sub-Himalayan regions and southwards to Godavari, India commonly known as Harsingar and Night Jasmine. In continuation of our drug discovery programme on Indian medicinal plants, we isolated arbortristoside-A (1) and 7-O-trans-cinnamoyl 6β-hydroxyloganin (2) from the seeds of N. Arbortristis, which exhibited moderate in vitro anticancer activity. Chemical transformation of 2 led to significant improvement in the activity in derivative 8 and 15 against HepG2 (human hepatocellular carcinoma), MCF-7 (breast adenocarcinoma) cell lines. The compounds 8 and 15 were also capable of cell cycle arrest and caspase dependent apoptosis in HepG2 cell lines. These iridoid derivatives hold promise for developing safer alternatives to the marketed drugs.

In vitro anti-hyperglycemic activity of 4-hydroxyisoleucine derivatives.

The nonproteinogenic amino acid, 4-hydroxyisoleucine (1) has been isolated in large quantities from the fenugreek (T. foenum-graecum) seeds. Few novel derivatives (3-11 and 13-18) were prepared from the naturally occurring 4-hydroxyisoleucine (1) and screened for their in vitro glucose uptake stimulatory effect in L-6 skeletal muscle cells. The derivatives 6, 7, 8, 10 and 11 exhibited better glucose uptake stimulatory activity than parent compound, 4-hydroxyisoleucine at 5 and 10µM concentrations and compounds 7 and 11 enhanced translocation of insulin sensitive glucose transporters-4 in skeletal muscle cells.

Anti-malarial Activity of New Emodin Derivatives against Plasmodium falciparum Chloroquine Resistant Strain

Emodin (1) is the major bioactive compound of several herb species, which belongs to anthraquinone class of compound. As a part of our drug discovery program, large quantities of emodin (1) was isolated from the roots of Rheum emodi and a library of novel emodin derivatives 2–24 were prepared to evaluate their in-vitro antimalarial activity, among them, compound 17, 18 and 20 showed potent antimalarial activity against chloroquine resistant strain PfK1with the IC50 of 2.28, 2.49 and 2.48 μM respectively with a high safety index.