Biotransformation of abietic acid by fungi and biological evaluation of its metabolites

Biotransformation of abietic acid was carried out initially using 28 different microbial strains. Among the evaluated, Mucor ramannianus produced a known metabolite 2α-hydroxy-dehydroabietic acid whereas Neurospora crassa yielded two known metabolites of 7β-hydroxy-dehydroabietic and 1β-hydroxy-dehydroabietic acids in 12.7, 15.5 and 20.1% yields, respectively. The in vitro antimicrobial activities of the metabolites were evaluated against 19 different pathogenic microorganisms, resulting in moderate inhibitory activity when compared to the standards, with MICs > 250 μg/mL. However, in the in vitro anticancer activity studies, 2α-hydroxy-dehydroabietic acid was found to be the most effective derivative against A549 human lung adenocarcinoma cell line with an IC₅₀ value of 320.8 μg/mL and SI (Selectivity index) of 156, respectively. Using the same assay and conditions, 7β-hydroxy-dehydroabietic was found to be the most effective and selective antiproliferative agent against HepG2 cell line with an IC₅₀ value of 196.6 μg/mL and SI of 187, respectively. Contrary to the antimicrobial activity, the biotransformation metabolites showed promising results suggesting selective toxicity against specific cancer cell line where the genotoxicity of the same derivatives were in a negligible range. Furthermore, DNA synthesis inhibition of metabolites were more promising in the A549 cell line while apoptotic effects were better in HepG2 cell line.