Hypersaline environments are known to support diverse fungal species from various orders. The production of secondary metabolites is one of the strategies that fungi adopt to thrive under such extreme environments, bringing up the stress tolerance response. Some such unique secondary metabolites also exhibit clinical significance. The increasing prevalence of drug resistance in cancer therapy demands further exploration of these novel bioactive compounds as cancer therapeutics. In the present study, a total of 31 endophytic fungi harboring inside red, green, and brown marine algae have been isolated and identified. The maximum likelihood analysis and diversity indices of fungal endophytes revealed the phylogenetic relationship and species richness. The genus Aspergillus was found to be the dominating fungus, followed by Cladosporium spp. All the isolated endophytic fungal extracts were tested for their cytotoxicity against HeLa and A431 cancer cell lines. Nine isolates were further analyzed for their cytotoxic activity from the culture filtrate and mycelia extract. Among these isolates, Biscogniauxia petrensis showed potential cytotoxicity with CC50 values of 18.04 and 24.85 μg/ml against HeLa and A431 cells, respectively. Furthermore, the media and solvent extraction optimization revealed the highest cytotoxic active compounds in ethyl acetate extract from the potato dextrose yeast extract broth medium. The compound-induced cell death via apoptosis was 50–60 and 45% when assayed using propidium iodide-live/dead and loss of mitochondrial membrane potential assay, respectively, in HeLa cells. Four bioactive fractions (bioassay-based) were obtained and analyzed using chromatography and spectroscopy. This study reports, for the first time, the cytotoxic activity of an endophytic fungal community that was isolated from marine macro-algae in the Rameswaram coastal region of Tamil Nadu, India. In addition, B. petrensis is a prominent apoptotic agent, which can be used in pharmaceutical applications as a therapeutic.

A perceived drawback of ruthenium(II) polypyridyl photosensitizers for phototherapeutic applications is their inadequate absorption in the visible region. Ru(II) dyads attached to lightharvesting organic chromophores are studied to address this issue. Biotin-appended compounds having one chromophore, namely BODIPY (boron-dipyrromethene) (1) and Ru(II)-(tpy) 2 (2), or a dyad system containing BODIPY linked to Ru(II)-(tpy) 2 via a diphenylacetylene linker (3) were prepared and studied as photodetection agent and photosensitizes for Photodynamic Therapy (PDT) applications. The bichromophoric 3 with a strong absorption profile (ɛ � 71000 M À 1 cm À 1 at λ max = 503 nm) and high singlet oxygen quantum yield (Φ Δ = 0.63 in DMSO) was studied for PDT activity. This complex produced a superoxide anion radical via type-I and singlet oxygen via type-II photosensitization processes on light exposure, as evidenced from DNA photo-cleavage experiments and in vitro DCFDA assay using reactive oxygen species scavengers/quenchers. Dyad 3 displayed an apoptotic photo-cytotoxic effect against HeLa and H1299 cancer cells with a photocytotoxicity index (PI) value of > 625 in HeLa cells with a PDT efficacy much superior to those of its monochromophoric analogs 1 and 2. The intrinsic emission of complex 3, utilized for cellular imaging, showed selectivity towards lysosomes. Finally, the remarkable potential of complex 3 was evidenced using a clinically relevant 3D multicellular tumor spheroid model.

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