Resveratrol (5-[(E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol), a redox active phytoalexin with a large number of beneficial activities is also known for antibacterial property. However the mechanism of action of resveratrol against bacteria remains unknown. Due to its extensive redox property it was envisaged if reactive oxygen species (ROS) generation by resveratrol could be a reason behind its antibacterial activity. Employing Escherichia coli as a model organism we have evaluated the role of diffusible reactive oxygen species in the events leading to inhibition of this organism by resveratrol. Evidence for the role of ROS in E. coli treated with resveratrol was investigated by direct quantification of ROS by flow cytometry, supplementation with ROS scavengers, depletion of intracellular glutathione, employing mutants devoid of enzymatic antioxidant defences, induction of adaptive response prior to resveratrol challenge and monitoring oxidative stress response elements oxyR, soxS and soxR upon resveratrol treatment. Resveratrol treatment did not result in scavengable ROS generation in E. coli cells. However, evidence towards membrane damage was obtained by potassium leakage (atomic absorption spectrometry) and propidium iodide uptake (flow cytometry and microscopy) as an early event. Based on the comprehensive evidences this study concludes for the first time the antibacterial property of resveratrol against E. coli does not progress via the diffusible ROS but is mediated by site-specific oxidative damage to the cell membrane as the primary event.

Clinical and preclinical data reveal that RECQL5 protein overexpression in breast cancer was strongly correlated with poor prognosis, survival, and therapeutic resistance. In the current investigation, we report design, synthesis, and specificity of a small molecule, 4a, which can preferentially kill RECQL5-expressing breast cancers but not RECQL5 knockout. Our stringent analysis showed that compound 4a specifically sensitizes RECQL5-expressing cancers, while it did not have any effect on other members of DNA RECQLhelicases. Integrated approaches of organic synthesis, biochemical, in silico molecular simulation, knockouts, functional mutation, and rescue experiments showed that 4a potently inhibits RECQL5-helicase activity and stabilizes RECQL5-RAD51 physical interaction, leading to impaired HRR and preferential killing of RECQL5-expressing breast cancer. Moreover, 4a treatment led to the efficient sensitization of cisplatin-resistant breast cancers but not normal mammary epithelial cells. Pharmacologically, compound 4a was orally effective in reducing the growth of RECQL5-expressing breast tumors (human xenograft) in NUDE-mice with no appreciable toxicity to the vital organs.

Synthetic strategies were developed for the preparation of indolo‐imine boron difluoride (IIBD) dyes based on indolo[3,2‐b]carbazole structures. Four new IIBD dyes were synthesized and were subsequently converted into the corresponding ‐BPh2/‐BOR2 and N‐t‐Boc/N‐benzoyl derivatives. The photophysical properties of all dyes were determined in both solution and solid media. All dyes absorb in the UV/Vis region, show negative solvatochromism, and are fluorescent in both media. The absorbance and fluorescence properties of the dyes can be tuned over a wide range by synthetic modifications. These findings are rationalized by theoretical calculations that correspond well to the experimental shifts, explain the negative solvatochromism, and allow quantification of charge transfer (CT). Similarly, the HOMO–LUMO energies measured by CV are in good agreement with the theoretically calculated values. Interestingly, the energy gaps of the dyes can also be tuned by structural modulations using the developed chemical route. Charge transport properties of the dyes were checked and showed that the N‐benzoyl derivative has the highest hole mobility which is useful for organic field effect transistor (OFET) applications. In addition, easy cellular uptake of the dyes, their low toxicity and high stability inside the cells associated with bright fluorescence in the cytoplasm will be useful for their future application as cellular imaging agents. All of these aspects highlight the interest of this new class of dyes.

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Management of the gastro-toxicity of non-steroidal anti-inflammatory drugs (NSAIDs) remains a crucial problem, because the commercially available anti-ulcer drugs have side effects and are often expensive. Hence, the potential of a new water-soluble GPx mimic, DL-trans-3,4-dihydroxy-1-selenolane (DHS(red)) in healing the indomethacin-induced stomach ulceration in mice was examined. Administration of indomethacin (18 mg/kg, p. o.) induced ulceration in the glandular portion of the gastric mucosa, accompanied by increased lipid peroxidation (1.3-fold, p <0.001) and protein oxidation (1.5-fold, p < 0.001), depletion of thiol-defense (42.5%, p < 0.01), plasma total antioxidant status (53.4%, p < 0.001) and mucin (47.5%, p < 0.01), as well as reduced expressions of cyclooxygenases and prostaglandin synthesis (54.7%, p < 0.001) in the gastric tissues of mice. Daily oral administration of DHS(red) (2.5 mg/kg) or omeprazole (Omez) (3 mg/kg) for 3 days respectively produced ˜74% and 69% (p < 0.001) healing of the acute gastric ulceration. The test samples also significantly reversed all the adverse effects of indomethacin on the biochemical parameters. Apparently, the gastric ulcer healing action of DHS(red) and Omez was due to their antioxidant action and their ability to protect mucin and augment PG synthesis by upregulation of the COX isozymes. The results suggested that the non-toxic and inexpensive compound, DHS(red), may be a good candidate for further evaluation as a potent anti-ulcer drug.

Designing heavy‐atom‐free triplet photosensitizers (PSs) is a challenge for the efficient photodynamic therapy (PDT) of cancer. Helicenes are twisted polycyclic aromatic hydrocarbons (PAHs) with an efficient intersystem crossing (ISC) that is proportional to their twisting angle. But their difficult syntheses and weak absorption profile in the visible spectral region restrict their use as heavy‐atom‐free triplet PSs for PDT. On the other hand, boron‐containing PAHs, BODIPYs are highly recognized for their outstanding optical properties. However, planar BODIPY dyes has low ISC and thus they are not very effective as PDT agents. We have designed and synthesized fused compounds containing both BODIPY and hetero[5]helicene structures to develop red‐shifted chromophores with efficient ISC. One of the pyrrole units of the BODIPY core was also replaced by a thiazole unit to further enhance the triplet conversion. All the fused compounds have helical structure, and their twisting angles are also increased by substitutions at the boron centre. The helical structures of the BODIPY‐hetero[5]helicenes were confirmed by X‐ray crystallography and DFT structure optimization. The designed BODIPY‐hetero[5]helicenes showed superior optical properties and high ISC with respect to [5]helicene. Interestingly their ISC efficiencies increase proportionally with their twisting angles. This is the first report on the relationship between the twisting angle and the ISC efficiency in twisted BODIPY‐based compounds. Theoretical calculations showed that energy gap of the S1 and T1 states decreases in BODIPY‐hetero[5]helicene as compared to planar BODIPY. This enhances the ISC rate in BODIPY‐hetero[5]helicene, which is responsible for their high generation of singlet oxygen. Finally, their potential applications as PDT agents were investigated, and one BODIPY‐hetero[5]helicene showed efficient cancer cell killing upon photo‐exposure. This new design strategy will be very useful for the future development of heavy‐atom‐free PDT agents.

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