Payare L. Sangwan

Piperine analogs as potent Staphylococcus aureus NorA efflux pump inhibitors.

Based on our recent findings that piperine is a potent Staphylococcus aureus NorA efflux pump inhibitor (EPI), 38 piperine analogs were synthesized and bioevaluated for their EPI activity. Twenty-five of them were found active with potentiating activity equivalent or more than known EPIs like reserpine, carsonic acid and verapamil. The inhibitory mechanism of the compounds was confirmed by efflux inhibition assay using ethidium bromide as NorA substrate. The present communication describes the synthesis, bioevaluation and structure related activity of these efflux pump inhibitors.

Citral derived amides as potent bacterial NorA efflux pump inhibitors.

Monoterpene citral and citronellal have been used as starting material for the preparation of 5,9-dimethyl-deca-2,4,8-trienoic acid amides and 9-formyl-5-methyl-deca-2,4,8-trienoic acid amides. The amides on bioevaluation as efflux pump inhibitors (EPIs) against Staphylococcus aureus 1199 and NorA overexpressing S. aureus 1199B bacteria resulted in the identification of several of these as potent EPIs. Many of these amides have been shown to possess potency higher or equivalent to known EPIs such as reserpine, verapamil, carsonic acid, and piperine. In this communication, we report a convenient synthesis of alkenyl amides, their bioevaluation and identification as efflux pump inhibitors against S. aureus.

Ring A structural modified derivatives of withaferin A and the evaluation of their cytotoxic potential.

Regio-/stereoselective Michael addition to ring A of withaferin-A was performed using an optimized reaction procedure to synthesise a library of 2,3-dihydro,3-β-substituted withaferin-A derivatives. The analogues thus obtained were evaluated for in vitro cytotoxicity against various human cancer cell lines. 3-Azido analogue exhibited 35-fold increase (IC(50)=0.02-1.9 μM) in cytotoxicity against almost the entire cell lines tested when compared to the parent molecule. However, further modifications of 3-azido analogue with various alkynes under Husigens cycloaddition conditions generated a variety of triazole derivatives with reduced cytotoxicity.

Bakuchiol derivatives as novel and potent cytotoxic agents: A report

A library of 28 compounds comprising of acyl, amino, halo, nitro, styryl and cyclized derivatives of bakuchiol have been evaluated against a panel of eight human cancer cell lines. Bioevaluation studies have resulted in the identification of potent cytotoxic molecules exhibiting concentration dependent growth inhibition against leukemia cancer cells with best results observed for compounds 17 and 22 exhibiting IC(50) 1.8 and 2.0 μM respectively. As evident from various biological end-points, inhibition of cell proliferation by inducing G2/M cell cycle arrest, mitochondrial membrane disruption followed by DNA fragmentation and apoptosis is demonstrated.

Inhibition of phosphotidylinositol-3 kinase pathway by a novel naphthol derivative of betulinic acid induces cell cycle arrest and apoptosis in cancer cells of different origin

Betulinic acid (BA) is a pentacyclic triterpenoid natural product reported to inhibit cell growth in a variety of cancers. However, the further clinical development of BA got hampered because of poor solubility and pharmacological properties. Interestingly, this molecule offer several hotspots for structural modifications in order to address its associated issues. In our endeavor, we selected C-3 position for the desirable chemical modification in order to improve its cytotoxic and pharmacological potential and prepared a library of different triazoline derivatives of BA. Among them, we previously reported the identification of a potential molecule, that is, 3{1N(5-hydroxy-naphth-1yl)-1H-1,2,3-triazol-4yl}methyloxy betulinic acid (HBA) with significant inhibition of cancer cell growth and their properties. In the present study, we have shown for the first time that HBA decreased the expression of phosphotidylinositol-3 kinase (PI3K) p110α and p85α and caused significant downregulation of pAKT and of NFκB using human leukemia and breast cancer cells as in vitro models. Further it was revealed that PI3K inhibition by HBA induced cell cycle arrest via effects on different cell cycle regulatory proteins that include CDKis cyclins and pGSK3β. Also, this target-specific inhibition was associated with mitochondrial apoptosis as was reflected by the increased expression of mitochondrial bax, downregulated bcl2 and decreased mitochondrial levels of cytochrome c, together with reactive oxygen species generation and decline in mitochondrial membrane potential. The apoptotic effectors such as caspase 8, caspase 9 and caspase 3 were found to be upregulated besides DNA repair-associated enzyme, that is, PARP cleavage caused cancer cell death. Pharmacodynamic evaluation revealed that both HBA and BA were safe upto the dose of 2000 mg/kg body weight and with acceptable pharmacodynamic parameters. The in vitro data corroborated with in vivo anticancer activity wherein Ehrlich solid tumor showed that HBA as a more potent agent than BA without any body weight loss and mortality.

Diminutive effect on T and B-cell proliferation of non-cytotoxic α-santonin derived 1,2,3-triazoles: A report

α-Santonin derived new series of 1,2,3-triazoles synthesized through Azide-Alkyne Huisgen 1,3-dipolar cycloaddition reaction between substituted aryl azide and a propargylated α-desmotrosantonin were bio-evaluated for their diminutive effect on ConA induced T-cell and LPS induced B-cell proliferation. Interestingly, most of the synthesized compounds showed better immunosuppressant activity than α-santonin. Triazole derivatives 9, 10, 17, 18, 29, and 30 displayed significant diminutive effect on cell proliferation. Compounds 12 and 13 were found selective against ConA T-cell proliferation exhibiting >90% inhibition at 1 × 10(-6) M concentration. The present study resulted in identification of several triazole derivatives as effective immunosuppressive agents.

Ten marker compounds-based comparative study of green tea and guava leaf by HPTLC densitometry methods: antioxidant activity profiling.

High-performance thin layer chromatography (HPTLC) method for the separation and quantitative determination of ten markers (catechins, flavonoids, and phenolics) in different extracts of green tea and guava leaf has been developed and the antioxidant activity profiles of the two plant extracts have been determined. Ten marker compounds have been resolved using silica gel 60 F(254) plates, toluene/acetone/formic acid (5:4:1  v/v/v) for markers 1-6, and toluene/ethyl acetate/formic acid/methanol (3:3:0.8:0.2  v/v/v/v) for markers 7-10 as the mobile phases. The high-performance thin layer chromatography densitometry was performed at wavelengths of 282 and 285  nm for the markers 1-6 and 7-10, respectively. Potent antioxidant activity and the presence of phenolics and flavan-3-ols has been observed for the guava leaf extracts suggestive of its use as an alternate economical source of antioxidants over green tea--the well-established food additive/nutraceutical agent.

Simultaneous quantification of five marker compounds of Betula utilis stem bark using a validated high‐performance thin‐layer chromatography method

A sensitive, selective and robust densitometric high-performance thin-layer chromatographic method was developed and validated for five marker compounds, namely betulin, lupeol, oleanolic acid, 3-acetyloleanolic acid and β-sitosterol, known for their various therapeutic activities. The marker compounds have been isolated from the stem bark of Betula utilis, well characterized by the spectral analysis, and their simultaneous quantitative determination carried out by high-performance thin-layer chromatography (HPTLC) method. The resolution of marker compounds was carried out on silica-gel 60 plates, using n-hexane:ethyl acetate (8:2 v/v) as the mobile phase. The HPTLC densitometry was performed at 500-nm wavelength after the post chromatographic derivatization with ceric ammonium sulfate reagent. The optimized method provided good linear relation (r>0.9960) for all the investigated analytes. The method is simple, and reproducible, which may be applied for quantitative analysis of the above-mentioned marker compounds.

Substituted dihydronaphthalenes as efflux pump inhibitors of Staphylococcus aureus.

A new series of 3-(substituted-3,4-dihydronaphthyl)-2-propenoic acid amides has been prepared through convergent synthetic strategies and tested in combination with ciprofloxacin against NorA overexpressing Staphylococcus aureus 1199B as test strain for potentiating of the drug activity. Out of 24 compounds evaluated, 12 compounds potentiated the activity of ciprofloxacin and resulted in 2-16 fold reduction in the MIC (4-0.5 microg/mL) of the drug. The failure of these efflux pump inhibitors (EPIs) to potentiate the activity of ciprofloxacin when tested against NorA knock out S. aureus SA-K1758 established their identity as NorA inhibitors. The structure of all these newly synthesised compounds was confirmed by spectral data. The present communication describes the synthesis, bioevaluation, structure activity relationship and mechanism of action of these EPIs.

Simultaneous quantification of eight bioactive secondary metabolites from Codonopsis ovata by validated high performance thin layer chromatography and their antioxidant profile

Chemical investigation of Codonopsis ovata resulted in the isolation and identification of β-sitosterol-3-O-glycoside, luteolin, apigenin, gentiacaulein, swertiaperenine, β-sitosterol, taraxeryl-3-acetate, and 3β-acetoxyoleanane-12-one. A rapid, precise, sensitive and validated HPTLC method for simultaneous quantification of these natural products (NPs) was developed on silica-gel 60F254 plate using ternary solvent system, n-hexane:ethyl acetate:formic acid (10.5:3.5:0.43, v/v/v). Markers were quantified after post chromatographic derivatization with cerric ammonium sulfate reagent. The method was validated for accuracy, precision, LOD, LOQ and all calibration curves showed a good linear relationship (r>0.9924) within test range. Precision was evaluated by intra- and inter-day tests with RSDs <2.59%, accuracy validation recovery 92.43-99.50% with RSDs <1.00%. Apigenin was found major component (natural abundance: 1.103%) and β-sitosterol the least (0.0263%). The NPs displayed antioxidant activity with luteolin exhibiting maximum effect at 1μg/mL concentration (75.9% for DPPH and 43.7% for ABTS) and others at 10 and 25μg/mL, suggesting thereby their apparent potential use for the prevention of free radical induced diseases or as an additive element to food and pharmaceutical industry.