According to the structure of podophyllotoxin and its structure-function relationship, a novel tandem biotransformation process was developed for the directional modification of the podophyllotoxin structure to directionally synthesize a novel compound, 4-(2,3,5,6-tetramethylpyrazine-1)-4-demethylepipodophyllotoxin (4-TMP-DMEP). In this novel tandem biotransformation process, the starting substrate of podophyllotoxin was biotransformed into 4-demethylepipodophyllotoxin (product 1) with the demethylation of the methoxyl group at the 4 position by Gibberella fujikuroi SH-f13, which was screened out from Shennongjia prime forest humus soil (Hubei, China). 4-Demethylepipodophyllotoxin (product 1) was then biotransformed into 4-demethylpodophyllotoxone (product 2) with the oxidation of the hydroxyl group at the 4 position by Alternaria alternata S-f6, which was screened out from the gathered Dysosma versipellis plants in the Wuhan Botanical Garden, Chinese Academy of Sciences. Finally, 4-demethylpodophyllotoxone (product 2) and ligustrazine were linked with a transamination reaction to synthesize the target product 4-TMP-DMEP (product 3) by Alternaria alternata S-f6. Compared with podophyllotoxin (i.e., a 50% effective concentration [EC 50 ] of 529 M), the EC 50 of 4-TMP-DMEP against the tumor cell line BGC-823 (i.e., 0.11 M) was significantly reduced by 5,199 times. Simultaneously, the EC 50 of 4-TMP-DMEP against the normal human proximal tubular epithelial cell line HK-2 (i.e., 0.40 M) was 66 times higher than that of podophyllotoxin (i.e., 0.006 M). Furthermore, compared with podophyllotoxin (i.e., log P ؍ 0.34), the water solubility of 4-TMP-DMEP (i.e., log P ؍ 0.66) was significantly enhanced by 94%. For the first time, the novel compound 4-TMP-DMEP with superior antitumor activity was directionally synthesized from podophyllotoxin by the novel tandem biotransformation process developed in this work.Podophyllotoxin (PTOX) is a naturally occurring aryltetralin lignan, and interest in it has been heightened by its potential antitumor activity (3, 16) but has failed to be used in human clinical trials because of unacceptable gastrointestinal toxic side effects (3). In order to overcome these limitations, numerous studies of Podophyllum lignans currently focus on the structural modification of the cycloparaffin (C ring) in the tetranap skeleton and the benzene with three methoxyl groups (E ring) to generate derivatives with superior pharmacological profiles (25). Aromatic heterocyclic compounds substituted with a carbon-nitrogen (CON) bond at the 4 position (14) may be a very effective pathway for improving the antitumor activity of PTOX, and most of these derivatives were more active than etoposide (1,5,7,8,15,20), which is a clinically important anticancer drug. Furthermore, previous investigations indicated that a PTOX derivative in which the para-position methoxyl group (4Ј-MeO) of PTOX was demethylated shows stronger anticancer activity and solubility than PTOX (29, 39). All of these analyses suggested that...