Novel bioconversion products of andrographolide by Aspergillus ochraceus and their cytotoxic activities against human tumor cell lines

Andrographolide (1), a major labdane diterpenoidal constituent of a famous traditional Chinese of Andrographis paniculata, exhibits a wide spectrum of biological activities including antibacterial, anti-inflammatory, and antitumor properties. Bioconversion of andrographolide (1) by Aspergillus ochraceus (ATCC 1008) was investigated. Five bioconversion products were isolated and identified. Their structures were identified to be 8β-hydroxy-8(17)-dihydroandrographolide (2), 8β-hydroxy-8(17)-dihydro-14-deoxy-11,12-didehydroandrographolide (3), 8β-hydroxy-8(17)-dihydro-14-deoxy-11,12-didehydroandrographolide 19-oic acid (4), 14-deoxy-11,12-didehydroandrographolide (5), and 14-deoxy-11,12-didehydroandrographolide 19-oic acid (6). Metabolites 2–4 were novel compounds. The proposed biosynthetic pathways of andrographolide by A. ochraceus were drawn. Most bioconversion products showed potential cytotoxic activities against human breast cancer (MCF-7), human colon cancer (HCT-116) and leukemia (HL-60) cell lines.