BIOTRANSFORMATION OF PODOPHYLLUM LIGNANS IN CELL-SUSPENSION CULTURES OF FORSYTHIA-INTERMEDIA

Biotransformation studies using cell suspension cultures of Forsythia intermedia showed these are capable of rapidly oxidizing the aryltetralin lactone lignan podophyllotoxin into podophyllotoxone. Smaller amount of the stereoisomer picropodophyllone were also produced, probably due to pH changes in the culture during incubation. These ketone products were obtained in up to 40% overall yield. Similar products were obtained when acetylpodophyllotoxin or podophyllotoxin 4-O-glucoside were fed to the cultures, demonstrating the presence of additional esterase and beta-D-glucosidase activities. Picropodophyllin was similarly transformed into picropodophyllone. Desoxpodophyllotoxin was converted into podophyllotoxone, presumably via benzylic hydroxylation prior to the oxidation. Traces of the proposed hydroxy intermediate were detected. Lignans containing phenolic groups when added to the cultures rapidly disappeared without yielding any biotransformation products, and were presumably catabolized. Transformation of podophyllotoxin into podophyllotoxone and picropodophyllone was optimal using cells in exponential phase and a 24 hr feeding period.