Browsing by Author "Velmathi, Sivan"

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    An isophorone-derived AIE-active probe for peroxynitrite detection and bioimaging applications
    (Royal Society of Chemistry, 2025-07-11) Lalitha, Raguraman; Vivek, Vishnu Halnor; Lu, Yueh-Hsun; Wu, Shu Pao; Velmathi, Sivan
    Compounds exhibiting aggregation-induced emission (AIE) are remarkable due to their characteristic restriction of intramolecular rotation, making them highly versatile for a wide range of applications. Herein, an isophorone based probe (IHP) was developed for the detection of peroxynitrite (ONOO−) using the C 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 N as the reactive group. Photophysical investigations were conducted to explore the aggregation behaviour of IHP in two different solvent systems: DMSO:PBS and DMSO. In DMSO, only the monomeric form of the dye was observed, showing no unusual behaviour. However, in DMSO : PBS (1 : 1), multiple emitting species were detected, indicating the coexistence of dye aggregates and monomers. The fluorescence spectra exhibited wavelength-dependent changes, with the aggregates displaying a red-shift compared to the monomers, indicating J-aggregation. The AIE properties of IHP resulted in red emission, with a fluorescence response towards ONOO− through oxidative cleavage of the C N bond to an aldehyde accompanied by the shift in emission maximum. Under physiological conditions, the probe exhibited good selectivity and high sensitivity to ONOO−, low detection limit of 1.1 μM and rapid recognition within 200 seconds. Furthermore, the probe was effectively used to image exogenous and endogenous peroxynitrite in living cells. © 2025 The Royal Society of Chemistry.
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    Naphthalimide based smart sensor for CN-/Fe3+ and H2S. Synthesis and application in RAW264.7 cells and zebrafish imaging
    (Royal Society of Chemistry, 2020-02-28) Naha, Sanay; Wu, Shu-Pao; Velmathi, Sivan
    Achieving selective detection of target analytes in aqueous media continues to be an arduous proposition. Herein, we report the conceptualization and synthesis of a novel tailor-fit molecular probe R based on 1,8-naphthalimide which acts as a trifunctional molecular sensor for CN-, Fe3+ and H2S. R shows colorimetric and fluorometric "on-off" relay recognition for CN- (red colour and orange emission) and Fe3+ (no colour and no emission) in 5% H2O + DMSO medium which is experimentally ascertained to be a tandem deprotonation-protonation process and is supported by 1H-NMR titration. Among all RSS (Reactive Sulphur Species), R shows selectivity for H2S through red colouration. Other coexistent anions, cations and RSS cause no discernible perturbation to the detection process. The detection of H2S is attributed to a chemodosimetric reduction of the nitro to amino group as evidenced by a potentiometric titration assay. The experimental observations are well supported by DFT theoretical calculation. The Ka for CN-/Fe3+ are 1.4 × 104 M-1, 6.07 × 104 M-1 respectively and photochemical yield of R + CN- is 0.86. Limit of detections for CN-, Fe3+ and H2S are 17.5 nM, 8.69 μM and 8.1 μM respectively. Receptor R is effective for real time applications, bio-compatible and has been successfully employed for confocal fluorescence imaging of RAW264.7 cell and zebrafish. This journal is © 2020 The Royal Society of Chemistry.
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    New spirooxindole pyrrolidine/pyrrolizidine analogs: design, synthesis, and evaluation as an anticancer agent
    (Royal Society of Chemistry, 2025-05-19) Nivetha, Narayanasamy; Venkatesan, Janarthanan; Murugan, Dhanashree; Rangasamy, Loganathan; Wu, Shu Pao; Velmathi, Sivan
    A novel series of mesitylene-based spirooxindoles were synthesized via the multicomponent [3 + 2] cycloaddition reaction in a greener medium. Spectroscopic techniques such as 1H and 13C NMR and HRMS analysis were carried out for the structural elucidation of all the spirooxindole derivatives. The in vitro cytotoxicity properties of spirooxindole analogs 4/5(a-g) against the human lung (A549) cancer cell line exhibited encouraging outcomes. Of the fourteen synthesized spirooxindole analogs, seven compounds (4a, 4b, 4e, 4g, 5c, 5e, and 5f) showed greater potency towards the A549 lung cancer cell line. The cytotoxicity of the spirooxindole analogs was also investigated against a non-cancerous mouse embryonic fibroblast NIH-3T3 cell line. Compounds 5e and 5f, which exhibited better cytotoxic effect against the cancerous A549 cells (3.48 and 1.2 μM), appeared to be non-cytotoxic against the non-cancerous mouse embryonic fibroblast. Studies using Hoechst and acridine orange/ethidium bromide staining also demonstrated the apoptotic effect of the potent compounds, which decreased cell proliferation. © 2025 The Royal Society of Chemistry.
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    One-pot three-component synthesis of novel phenyl-pyrano-thiazol-2-one derivatives and their anti-diabetic activity studies
    (Elsevier B.V., 2022-07-12) Prabhakaran, Srinivasan; Nivetha, Narayanasamy; Patil, Shashank M.; Mary Martiz, Reshma; Ramu, Ramith; Sreenivasa, Swamy c; Velmathi, Sivan
    An easy and rapid synthetic approach for the synthesis of phenyl-pyrano-thiazol-2-one derivatives using base catalysed one-pot three-component reaction between substituted aromatic aldehyde, N-methyl-1-(methylthio)-2-nitroethamine (NMSM) and thiazolidinedione is reported. Among the bases tested, piperidine was proven to be the most efficient organo-base catalyst, when ethanol was used as a solvent. The product was obtained in good yields and confirmed using FT-IR, NMR and mass spectroscopic techniques. The electron withdrawing group substituted product was obtained in higher yield compared to the electron donating group substituted product. The strategy used involved mild reaction conditions, shorter reaction time and easy isolation of products. The reaction sequence involved Knoevenagel condensation, Michael addition followed by intramolecular O-cyclization. © 2022 The Authors
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    Radical cascade cyclization of amino acid-tethered 1,6-enynones with sulfonyl hydrazides for N-terminal modification: synthesis of functionalized succinimide derivatives
    (Royal Society of Chemistry, 2025-08-01) Sivanantham, Mathiyazhagan; Jacob Stanley, Jenis; Muthu, Kesavan; Velmathi, Sivan; Senadi, Gopal Chandru; Senadi, Gopal Chandru; Ramasamy, Mohankumar
    A metal-free strategy for the N-terminal cyclization of amino acids has been developed by synthesizing highly functionalized succinimide derivatives through radical cyclization of amino acid-tethered 1,6-enynones with sulfonyl hydrazide using NIS and H2O2 as an oxidant. The notable advantages of this work includes time-efficient, good E/Z ratio, moderate to good yields, and was synthesized on a gram-scale. Furthermore, the synthetic utility of the product 5aa was performed by (i) Suzuki coupling reaction with iodo-functionality; and (ii) dipeptide formation using glycine methyl ester. © 2025 The Royal Society of Chemistry.
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    Sulfated magnesium zirconate catalyzed synthesis, antimicrobial, antioxidant, anti-inflammatory, and anticancer activity of benzo[d]thiazole-hydrazone analogues and its molecular docking
    (Elsevier B.V., 2021-09-20) Govindaiah, Shivaraja; Naha, Sanay; Madhuchakrapani Rao, Tadimety; Revanasiddappa B.C.; Srinivasa, Sudhanva M.; Parashuram, L; Velmathi, Sivan; Sreenivasa, Swamy
    A comprehensive demonstration of novel catalytic synthetic pathway using sulfated zirconia (solid acid catalyst) to generate a library of bioactive compounds precisely, the benzo[d]thiazole-hydrazone derivatives (4a-n). The compounds are characterized using ubiquitous spectroscopic techniques such as, IR, 1H and 13C NMR, HR-Mass. The set of molecules are screened in vitro biological activities namely, antimicrobial, antioxidant, anti-inflammatory and anticancer which are aptly supported by the molecular docking studies. Among the compounds, 4a and 4e are observed to be the most potent antibacterial agents where as 4a and 4c displayed significant antifungal activity. On the contrary, compounds 4e and 4j showed good antioxidant properties and 4b and 4j exhibited excellent anti-inflammatory activity. The compound 4d found to be a potent anti-cancer agent against tested human cancer cell lines MIAPaca2, HeLa, A549, and HCT116 (IC50 values of 19.09 ± 0.50, 19.93 ± 0.25, 7.76 ± 0.50, and 5.05 ± 0.25 μM respectively). Molecular docking studies were performed using DNA Gyrase, N-myristoyltransferase, COX-2, EGFR, HER2, and VEGFR2 proteins. Notably, compound 4d strongly binds to receptors EGFR and HER2 as inferred by their binding energies compared to standard inhibitors Gefitinib (EFGR), Lapatinib (EGFR), Afatinib (HER2), and Canertinib (HER2). © 2021