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Oxidative stress is an essential component of innate response against microbes. The oxidative impact has a very subtle connection with apoptosis. Our previous work indicated presumptive evidence of apoptosis by the chalcone derivatives against the human lymphatic filarial parasite. Evidence suggests the involvement of glutathione-S-transferase (GST) in the mechanism of action of chalcone drugs. In the present study, we explored the implications of redox status in apoptosis of the parasite by this drug. Treatment with the representative drug, 4t, significantly decreased GSH level and increased GST activity in the Brugia malayi microfilariae (Mf) in comparison to Mf without 4t treatment. Drug-induced loss of motility of the parasites was reversed by the treatment with GSH (41%) and NAC (19%). A significant fall in rGST activity was observed due to drug addition, which could be reversed by the addition of GSH co-substrate, but not with the re-addition of rGST, indicating a vital role of GSH. In silico study demonstrated a favorable drug–GST enzyme interaction. Oxidative stress was reflected by increased protein carbonylation and intracellular reactive oxygen species level, in the drug-treated parasite. Mitochondrial oxygen consumption was reduced by the drug, which was reversed on the addition of GSH. Mitochondrial dysfunction was confirmed by MTT and cytochrome c assay. Apoptosis was confirmed by the inhibition in PARP activity. We conclude that the depletion of GSH by chalcone with concomitant mitochondrial dysfunction revealed a novel rationale of apoptosis in the parasite. Such a mechanism might have wide therapeutic implications.

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with ortho-cyanomethylbenzaldehydes. These amine α-C–H bond functionalization reactions are promoted by acetic acid. The resulting β-aminonitriles can be converted to the corresponding β-aminoalcohols in diastereoselective fashion.

A novel library of synthetic piperidine derivatives was used to screen against human lymphatic filarial parasite Brugia malayi. Piperidine has earlier been reported to have effect against parasites including rodent filarial nematodes. Compounds with hydroxyl substitutions (4Q and 4H) showed marked antifilarial effect. Molecular docking of 4H derivative showed more favorable thermodynamic parameters against thymidylate synthase of B. malayi than human counterpart. A wide difference between IC50 and LD50 ensured the therapeutic safety of the candidates against the filarial parasites. Addition of thymidine to the treatment regimen led to a significant reversal of antifilarial effect of 4H that confirmed inhibition of thymidylate synthase as pharmacological rationale. Apoptosis induced in the parasite as a consequence of probable inhibition of thymidylate synthase was studied by acridine orange/ethidium bromide fluorescent staining and poly (ADP-ribose) polymerase activity inhibition. Involvement of mitochondria was confirmed by decreased 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) conversion and increased cytosolic cytochrome c level in 4H treated microfilariae, compared with the untreated microfilariae. Moreover, Michael adduct of chalcone targeting dihydrofolate reductase and piperidine targeting thymidylate synthase demonstrated synergistic effect on the parasite, indicating the importance of inhibition of DNA synthesis by combined effect. In conclusion, piperidine derivatives with hydroxyl substitution have a great therapeutic potential with an apoptotic rationale involving mitochondrial pathway, due to possible inhibition of parasitic thymidylate synthase.

Glutathione S-transferase omega 1 (GSTO1) contributes to the inactivation of a wide range of drug compounds via conjugation to glutathione during phase reactions. Chemotherapy-induced GSTO1 expression in breast cancer cells leads to chemoresistance and promotes metastasis. In search of novel GSTO1 inhibitors, we identified S2E, a thia-Michael adduct of sulfonamide chalcone with low LC50 (3.75 ± 0.73 μm) that binds to the active site of GSTO1, as revealed by molecular docking (glide score: -8.1), cellular thermal shift assay and fluorescence quenching assay (Kb ≈ 10 × 105 mol·L-1 ). Docking studies confirmed molecular interactions between GSTO1 and S2E, and identified the hydrogen bond donor Val-72 (2.14 A) and hydrogen bond acceptor Ser-86 (2.77 A). Best pharmacophore hypotheses could effectively map S2E and identified the 4-methyl group of the benzene sulfonamide ring as crucial to its anti-cancer activity. Lack of a thiophenyl group in another analog, 2e, reduced its efficacy as observed by cytotoxicity and pharmacophore matching. Furthermore, GSTO1 inhibition by S2E, along with tamoxifen, led to a significant increase in apoptosis and decreased migration of aggressive MDA-MB-231 cells, as well as significantly decreased migration, invasion and mammosphere formation in sorted breast cancer stem cells (CSCs, CD24- /CD44+ ). GSTO1 silencing in breast CSCs also significantly increased apoptosis and decreased migration. Mechanistically, GSTO1 inhibition activated the c-Jun N-terminal kinase stress kinase, inducing a mitochondrial apoptosis signaling pathway in breast CSCs via the pro-apoptotic proteins BAX, cytochrome c and cleaved caspase 3. Our study elucidated the role of the GSTO1 inhibitor S2E as a potential therapeutic strategy for preventing chemotherapy-induced breast CSC-mediated cancer metastasis and recurrence.

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with 2-(2-oxoethyl)malonates in the presence of catalytic amounts of benzoic acid. These reactions install a fully saturated five-membered ring and provide access to structures closely related to the natural products crispine A and harmicine.

Diethyl carbamazine (DEC) is being used as a sole drug to treat the lymphatic filariasis, although encountered with many limitations. Importantly, DEC works with putative host immunomodulating activities without any direct antifilarial effect. This study aimed to assess the possible modulatory effect on host immune system by sulfonamide chalcone compound, having direct antifilarial activity. The immunomodulatory activity of DEC and/or chalcone compound, 4t on mice peritoneal exudate cells (PECs) was analyzed initially in vitro. This was followed by the study of in vivo effect of these test agents in the parasitaemic BALB/c mice induced by Brugia malayi microfilariae. Cytokine profile and iNOS induction were measured from PECs of mice. 4t compound showed anti-inflammatory activity in vivo in contrast to DEC. Further 4t was found to increase anti-inflammatory and regulatory cytokines, IL-10 and TGF-β gene expression with down regulation of pro-inflammatory cytokines TNF-α and IFN-γ and iNOS in mice PECs in in vitro. In conclusion, chalcones having direct antifilarial effect also upsurges anti-inflammatory host immune response. Therefore, the results might be envisaged as 4t to be a better alternative to DEC in the chronic case of lymphatic filariasis.

Amines such as 1,2,3,4-tetrahydroisoquinoline undergo redox-neutral annulations with ortho-cyanomethylbenz-aldehydes. These amine α-C–H bond functionalization reactions are promoted by acetic acid. The resulting β-aminonitriles can be converted to the corresponding β-aminoalcohols in diastereoselective fashion.

Zinc(II) triflate catalyzed three-component coupling reactions of alkynes, amines and aldehydes leading to the formation of aryl/alkyl substituted quinolines has been described. Notably, the reaction proceeded efficiently and effectively without the use of ligand, co-catalyst, solvent or inert atmosphere. This robust solvent-free process operates under an ambient atmosphere and avoids the use of precious metals, hazardous solvents and harsh reaction conditions. This atom economic process eliminates the waste generated in the multistep synthesis. Additionally, a pseudo three-component Povarov reaction of amines and butanal proceeds under the same green conditions enabling the formation of 2,3-dialkyl quinolines.

Keeping in mind the immense biological potential of chalcones and sulfonamide scaffolds, a library of sulfonamide chalcones has been synthesized and evaluated for in vitro antifilarial assay against human lymphatic filarial parasite Brugia malayi. Experimental evidence showcased for the first time the potential of some sulfonamide chalcones as effective and safe antifilarial lead molecules against human lymphatic filarial parasite B. malayi. Sulfonamide chalcones 4d, 4p, 4q, 4t and 4aa displayed the significantly wide therapeutic window. Particularly chalcones with halogen substitution in aromatic ring proved to be potent antifilarial agents against Brugia malayi. Sulphonamide chalcones with lipophilic methyl moiety (4q and 4aa) at para position of terminal phenyl rings of compounds were found to have remarkable antifilarial activities with therapeutic efficacy. Observed preliminary evidence of apoptosis by effective chalcone derivatives envisaged its fair possibility to inhibit folate pathway with consequent defect in DNA synthesis.

Zn(OTf)2-mediated expeditious and solvent-free synthesis of propargylamines via A3 coupling of aldehydes, amines, and phenylacetylene has been described. The described protocol proceeds effectively with variety of substituted benzaldehydes, enolizable aldehyde, and formaldehyde. Recyclability of the catalyst, low catalyst loading, and use of inexpensive catalyst are the key features of the present protocol.

The synthesis of highly functionalized piperidines has been strategically accessed via organo-catalytic three components (in situ five components) reaction of an amine, aldehyde and 1,3-dicarbonyl compound. This imine based multi-component reaction was realized using fully green L-proline nitrate as recyclable room temperature ionic liquid. Recycling of the catalyst was possible up to five runs without loss of catalyst activity. Smaller E-factor (0.255) and process mass intensity (PMI = 3.35), high atom-economy (AE = 89.5%) and reaction mass efficiency (RME = 79.66%) demonstrates the higher environmental compatibility and sustainability of this protocol. DFT calculations showed that the L-proline catalyzed reaction proceeds by three pathways; (i) via proline enamine pathway, (ii) proline mediated aniline enamine pathway or (iii) the pathway involving iminium activation of the aldehyde to provide the Knoevenagel product.

Density functional theory calculations were carried out on fused oligothiophenes, their cation radicals and dications (singlet and triplet spin multiplicity) as well as fused polythiophene at B3LYP/6-31G(d) level of theory and compared with their selenophene analogues. The effective conjugation in both the series of fused oligomers was compared on the basis of ‘bond length alternation’ (BLA). Fused oligo- and polyselenophenes have a more quinoidal character and lower band gap (HOMO–LUMO gap) than their thiophene analogues. The band gaps of polymers were obtained by extrapolation of HOMO–LUMO gap versus 1/n. The deviation from 1/n dependence in HOMO–LUMO gaps starts from n ⩾ 31. Thus HOMO–LUMO gaps show convergence behavior. Similar to that of the linear non-fused oligomers of thiophene and selenophene, fused oligothiophene and -selenophene show linear relationship between the internal reorganization energy for self-exchange hole-transfer process (λ) and the square root of chain length only for short oligomers. For longer oligomers, it follows a linear relationship with the reciprocal of chain length and extrapolation gives λ ≈ 0 for polymers. The dications longer than 11-mer showed the RHF/UHF instability and it can be understood as the contribution of the polaron-pair state to the ground-state structure. The calculations suggest that triplet is never a ground state for fused oligothiophene and -selenophene dications. The polaron-pair contribution to the ground state of dication increases with chain length of fused oligothiophene and -selenophene. The triplet state and unrestricted singlet state become degenerate for longer fused oligothiophene and -selenophene, whereas for smaller fused oligomer (up to 20-mer) the singlet state dications are more stable than triplet state dications. The fused oligo- and polythiophene and -selenophene behave similar to the non-fused linear oligo- and polythiophene and -selenophene and do not behave like oligo- and polyacenes.

An l -proline nitrate assisted protocol is described for the construction of 2,3-dihydroquinazolin-4(1H)-ones. The catalyst can be recovered easily and is reusable for at least six cycles without significant loss of catalytic efficiency.

L-Proline nitrate is used as a green catalyst for a one-pot cyclocondensation of anthranilamide and aldehydes under mild conditions.

An environmentally benign, room temperature aqueous synthesis of pyrazoles by the condensation of hydrazines/hydrazides with 1,3-diketones using Amberlyst-70 as a recyclable catalyst is described. The use of resinous, non-toxic, thermally stable and inexpensive Amberlyst-70 as a heterogeneous catalyst and simple reaction workup are the additional eco-friendly attributes of this synthetic protocol.

An environmentally benign aqueous protocol for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones using Amberlyst-70 as a recyclable catalyst has been developed. The use of resinous, nontoxic, thermally stable and inexpensive Amberlyst-70, as a recyclable heterogeneous catalyst, makes the process simple with negligible chemical waste. Thus renders this method an environmentally acceptable synthetic tool for Biginelli reaction.

The application of the ionic liquid L-proline nitrate as catalyst for the pseudo-five component reaction of aromatic aldehydes, anilines, and β-dicarbonyl compounds is demonstrated.

Two new phenyl capped cyclopenta[c]chalcogenophenes (PhCPTPh and PhCPSPh) were synthesized by zirconocene mediated coupling and characterized by single crystal X-ray diffraction (SCXRD). Replacement of sulfur by selenium destabilized the HOMO level and increased the structural rigidity. The crystal structures of both the compounds were found to be nearly planar. PhCPSPh, though isostructural with PhCPTPh, packed in a very-ordered and specific pattern by Se⋯π interactions between two neighboring molecules. Hirshfeld surface analysis supported the crystal structure study. Theoretical calculations exhibited very close reorganization energies of 0.23 and 0.22 eV for PhCPTPh and PhCPSPh, respectively.