Unique secondary metabolites have been discovered in abundance from marine habitats, particularly from organisms housing endophytes. Some of the compounds are being evaluated as possible anticancer treatments leads by the pharmaceutical sector. Herein, we describe Biscogniauxia petrensis, an uncommon endophytic fungus discovered in Halimeda macroloba, green macroalgae from the Bay of Bengal. Screening for cytotoxicity against human cancer cell lines revealed the cytotoxic concentration (CC50) values of 18.04 and 24.85 µg/ml for HeLa and A431 cells, respectively, demonstrating the potency of Biscogniauxia petrensis secondary metabolites. The optimization of growing media and extraction solvent indicated that ethyl acetate extracts from the potato dextrose yeast extract broth medium had the utmost cytotoxic compounds. The bioactive guided purification, exposed two fractions (C2 and M4) from culture filtrate and mycelia extract with the highest impact against HeLa at CC50 values of 31.18 and 25.52 g/ml, respectively, and no toxicity to non-cancerous cells (HEK-293). Both the compounds (C2 and M4) inhibited cell growth by arresting the cell cycle in the Sub-G1 phase in HeLa. Microscopic observation of HeLa cells treated with C2 and M4 shown features of apoptosis-like loss of membrane integrity, blebbing, and chromatin condensation. Additional results from various experiments like Annexin V FITC/PI, MMP loss, and DNA fragmentation collectively proposed the apoptotic cell death, confirmed by Caspase 3/7 activation assay and western blot analysis, showing the upregulation of pro-apoptotic proteins such as PARP1, P53, Bax, Apaf-1 and caspases (3, 8, 9). Finally, NMR data revealed the molecular structure of compounds C2 and M4 with names like 4-((7-amino-7-oxoheptyl)oxy)methylene)-1,2,3,4- tetrahydroquinoline-5-carboxylic acid (AMTCA) and Heptadecanamide respectively, ), both of which turned out to be novel compounds.
KEYWORDS: Marine natural products, algicolous endophytic fungi, Biscogniauxia petrensis, Cancer, Novel Chemotherapeutics