Ritu Ojha

Vasicine and structurally related quinazolines

Natural products are diverse sources of important chemical constituents. Most of the metabolites isolated from them are heterocycles possessing diverse pharmacological actions. Vasicine, a heterocyclic alkaloid possessing a privileged quinazoline nucleus is primarily present in the leaves o the plant Adhatoda vasica nees, family Acanthaceae. Vasicine and structurally related quinazolines have been an area of interest for the researchers all around the world. The present review provides an up to date compilation of the alkaloid vasicine, its biosynthesis, synthesis, biological attributes, design of its synthetic analogues along with structurally related quinazolines.

Synthesis and evaluation of naphthoflavones as a new class of non purine xanthine oxidase inhibitors

In view of reported xanthine oxidase inhibitory potential of naphthopyrans and flavones, naphthoflavones as hybrids of the two were designed, synthesized and evaluated for in vitro xanthine oxidase inhibitory activity in the present study. The results of the assay revealed that the naphthoflavones possess promising inhibitory potential against the enzyme with IC50 values ranging from 0.62 to 41.2 μM. Structure activity relationship indicated that the nature and placement of substituents on the phenyl ring at 2nd position remarkably influences the inhibitory activity. Substitution of halo and nitro groups at ortho and para position of the phenyl ring (2nd position) remarkably favored the activity. NF-4 with p-fluoro phenyl ring was the most potent inhibitor with IC50 value of 0.62 μM. Enzyme kinetics study was also performed to investigate the inhibition mechanism and it was found that the naphthoflavones displayed mixed type inhibition. The basis of significant inhibition of xanthine oxidase by NF-4 was rationalized by molecular modeling studies.

Microwave assisted synthesis of naphthopyrans catalysed by silica supported fluoroboric acid as a new class of non purine xanthine oxidase inhibitors.

A series of naphthopyrans was synthesized employing silica supported fluoroboric acid under solvent free conditions in a microwave reactor. The catalytic influence of HBF4-SiO2 was investigated in detail to optimize the reaction conditions. The synthesised compounds were evaluated for in vitro xanthine oxidase inhibitory activity for the first time. Structure-activity relationship analyses have also been presented. Among the synthesised compounds, NP-17, NP-19, NP-20, NP-23, NP-24, NP-25 and NP-26 were the active inhibitors with an IC50 ranging from 4 to 17 μM. Compound NP-19 with a thiophenyl ring at position 1 emerged as the most potent xanthine oxidase inhibitor (IC50=4 μM) in comparison to allopurinol (IC50=11.10 μM) and febuxostat (IC50=0.025 μM). The basis of significant inhibition of xanthine oxidase by NP-19 was rationalized by its molecular docking at MTE binding site of xanthine oxidase.

Tubulin inhibitors: a patent survey.

Tubulin is one of the most useful and strategic molecular targets for anticancer drugs. The dynamic process of microtubule assembly and disassembly can be blocked by various agents that bind to distinct sites in the β-tubulin subunit. By interfering with microtubule function in vitro, these agents arrest cells in mitosis, eventually leading to cell death, by both apoptosis and necrosis. So far, three binding domains have been identified a) the colchicine site close to the α/β interface, b) the area where the vinca alkaloids bind, and c) the taxane-binding pocket. This review compiles the patent literature up to 2013 and offers a detailed account of all the advances on Tubulin inhibitors (lead molecules) along with in depth knowledge about the number of novel scaffolds, modified analogs and derivatives of the lead molecules. Colchicine binding site remains the most explored site indicated by the patent survey as majority of the patents revolves around phenstatin and combretastatin based molecules where the key structural feature for tubulin inhibition is an appropriate arrangement of the two aromatic rings at an appropriate distance and optimal dihedral angle maximizing interactions with tubulin. A brief account of promising tubulin inhibitors in stages of clinical development and some strategies for the development of potent molecules overcoming the problem of drug resistance have also been discussed.

Design strategies, structure activity relationship and mechanistic insights for purines as kinase inhibitors.

Kinases control a diverse set of cellular processes comprising of reversible phosphorylation of proteins. Protein kinases play a pivotal role in human tumor cell proliferation, migration and survival of neoplasia. In the recent past, purine based molecules have emerged as significantly potent kinase inhibitors. In view of their promising potential for the inhibition of kinases, this review article focuses on purines which have progressed as kinase inhibitors during the last five years. A detailed account of the design strategies employed for the synthesis of purine analogs exerting inhibitory effects on diverse kinases has been presented. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the purine analogs for kinase inhibition. The interactions with the amino acid residues responsible for kinase inhibitory potential of purine based molecules have also been discussed. In this assemblage, purine based protein kinase inhibitors patented in the past have also been summarized in the tabular form. This compilation will be of great interest for the researchers working in the area of protein kinase inhibitors.

4,6-Diaryl/heteroarylpyrimidin-2(1H)-ones as a new class of xanthine oxidase inhibitors.

A series of 4,6‐diaryl/heteroarylpyrimidones was synthesized employing silica‐supported fluoroboric acid under solvent‐free conditions in a microwave reactor. The catalytic influence of HBF4‐SiO2 was investigated in detail to optimize the reaction conditions. The synthesized compounds were evaluated for in vitro xanthine oxidase (XO) inhibitory activity for the first time. Structure‐activity relationship analyses are also presented. Among the synthesized compounds, VA‐5, ‐9, ‐10, ‐12, ‐22, ‐23, and ‐25 were the active inhibitors with IC50 values ranging from 6.45 to 13.46 µM. Compound VA‐25 with a pyridinyl ring as ring A and a thiophenyl ring as ring B emerged as the most potent XO inhibitor (IC50 = 6.45 µM) in comparison to allopurinol (IC50 = 12.24 µM). Some of the important interactions of VA‐25 with the amino acid residues of the active site of XO were figured out by molecular modeling studies.

Effect of ring A and ring B substitution on the cytotoxic potential of pyrazole tethered chalcones

Chalcone is an aromatic ketone that forms the central core for a variety of important biological compounds, which are collectively known as chalcones. The cytotoxic potential of chalcones which consists of C6–C3–C6 units gets enhanced by the incorporation of pyrazole ring as proved by our earlier studies. Thus in the present work, pyrazoles of chalcones with ring A substituted by furan, naphthalene and variety of substituted phenyl rings has been prepared and evaluated for in vitro cytotoxic activity against PC-3, OVCAR, IMR-32, HEP-2 human cancer cell lines.Graphical abstractAll the synthesized compounds were evaluated for in vitro cytotoxicity against PC-3, OVCAR, IMR-32, HEP-2 human cancer cell lines. Compound 68 was found to be the most potent showing broad spectrum of cytotoxicity against all the cell lines .

An updated patent review: xanthine oxidase inhibitors for the treatment of hyperuricemia and gout (2011-2015)

ABSTRACT Introduction: Xanthine oxidase (XO) is a versatile molybdoflavoprotein, widely distributed, occurring in milk, kidney, lung, heart, and vascular endothelium. Catalysis by XO to produce uric acid and reactive oxygen species leads to many diseases. Anti hyperuricemic therapy by xanthine oxidase inhibitors has been mainly employed for the treatment of gout. Area covered: This review covers the patent literature (2011–2015) and also presents the interesting strategies/rational approaches employed for the design of xanthine oxidase inhibitors reported recently. Expert opinion: Recent literature indicates that various non purine scaffolds have been extensively investigated for xanthine oxidase inhibition. The significant potential endowed by heteroaryl based compounds, in particularly fused heterocycles clearly highlights their clinical promise and the need for detailed investigation. Studies by various research groups have also revealed that the flavone framework is open for isosteric replacements and structural modifications for yielding potent non purine xanthine oxidase inhibitors. In addition, various plant extracts recently reported to possess significant xanthine oxidase inhibitory potential presents enough promise to initiate a screening program for the identification of other plant extracts and phytoconstituents possessing inhibitory potential towards the enzyme.