Alternaria alternata (SDHY01/02), a fungus associated with Lamellodysidea herbacea: its anticancer potential and responsible constituent(s)

Abstract

One of the biggest global causes of death is cancer. The side effects of currently available therapies have triggered the search for new drugs. The marine environment, with its vast biodiversity, including sponges, is a rich source of natural products with immense pharmaceutical potential. The aim of the study was to analyze the microbes associated with the marine sponge, Lamellodysidea herbacea, and explore them as resources for anticancer ability. This study includes the isolation of fungi from L. herbacea, and their evaluation for cytotoxic potential against human cancer cell lines such as A-549 (lung), HCT-116 (colorectal carcinoma), HT-1080 (Fibrosarcoma), and PC-3 (prostate) using MTT assay. This revealed that fifteen extracts showed significant anticancer ability (IC₅₀ ≤ 20 µg/mL), at least against one of the cell lines. Three extracts, SPG12, SPG19, and SDHY 01/02, were found significant in terms of anticancer activity, at least against three to four cell lines (IC₅₀ values ≤ 20 µg/mL). The fungus SDHY01/02 was identified by sequencing the internal transcribed spacer (ITS) region as Alternaria alternata. Its extract showed IC₅₀ values < 10 µg/mL against all the tested cell lines and was further analysed through light and fluorescence microscopy. The extract of SDHY01/02 was active (lowest IC₅₀ 4.27 µg/mL) against A549 cells in a dose-dependent manner and caused apoptotic cell death. Further, the extract was fractionated and analyzed the constituents by GC-MS (Gas Chromatography-Mass Spectrometry). Di-ethyl ether fraction revealed the constituents (having anticancer activity) such pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methyl propyl); 4,5,6,7-tetrahydro-benzo[C]rhiophene-1-carboxylic acid cyclopropylamide; 17-pentatriacontene; 9,12-octadecadienoic acid (Z, Z)-, methyl ester; while DCM fraction contained Oleic acid, eicosyl ester. This is the first report of A. alternata with anticancer potential that has been isolated from the sponge L. herbacea, as far as we are aware.This A. alternata can be exploited to get anticancer molecule(s) in the future.

Keywords: Cancer; Cytotoxicity; MTT assay; Phylogenetic analysis; SEM.