Optimization parameters for the production of dimer of epicatechin from an endophytic fungus Curvularia australiensis FC2AP using response surface methodology (RSM)

The search for natural therapeutic agents has intensified due to their potential to treat various diseases. Bioactive secondary metabolites from endophytes offer high therapeutic profiles and can be mass-produced after optimizing medium parameters and purification. This investigation aimed to maximize crude pigmented secondary metabolite (CPSM) production from Curvularia australiensis FC2AP by optimizing fermentation conditions statistically. The endophytic fungus produced a maximum yield of 8.81 UL/g from biomass using Sabouraud's Dextrose Broth. After screening essential factors, the Plackett-Burman design was used for factorial optimization, and the Box Behnken design was employed to investigate three significant factors. The final CPSM yield was 12.3 UL/g, approximately 4-fold higher than the preliminary growth medium. Chromatographic purification using a gradient solvent system resulted in six fractions, with the fourth fraction demonstrating the highest bioactivity profile. Structural characterization confirmed this fraction to be a dimer of epicatechin, which has anti-cancer properties, as confirmed through in vivo studies on Sprague Dawley rats. This is the first report of a epicatechin dimer produced from C. australiensis.