Pulchranin A: First report of isolation from an endophytic fungus and its inhibitory activity on cyclin dependent kinases.

Fungal factories emerge as a promising source for the production of bioactive natural products. This study reports the isolation and structure elucidation of pulchranin A, for the first time, from an endophytic fungus (Aspergillus TRL1), which was cultured from Tabebuia rosea (Bignoniaceae) stems and identified by DNA ITS sequencing. Pulchranin A showed promising in-vitro cytotoxic effects against breast (MCF-7), liver (Hep-G2) and colorectal (HCT) cell lines, with IC₅₀ values of 63, 80 and 91 µg/mL, respectively. In addition, it inhibited three cyclin-dependent kinases (CDK1, CDK2 and CDK4) in MCF-7 cells with IC₅₀ values of 9.82, 15.6 and 2.7 µg/mL, respectively. Results were further supported by in-silico molecular docking of pulchranin A to CDK1, CDK2, and CDK4 crystal structures, where it demonstrated good interactions by H-bonding, hydrophobic and Pi-Pi interactions with different amino acid residues of these enzymes. Pulchranin A might be a potential CDK inhibitor in human breast cancer cells.