Ginkgo biloba cell suspension cultures were used to biotransform 2α, 5α, 10β, 14β-tetra-acetoxy-4 (20),11-taxadiene. Two novel compounds were obtained and their structures were identified as 9α-hydroxyl-2α, 5α, 10β, 14β-tetra-acetoxy-4 (20), 11-taxadiene 1 and 9α, 10β-dihydroxyl-2α, 5α, 14β-tri-acetoxy-4 (20), 11-taxadiene 2, respectively, on the basis of their physical and chemical data. Compound 1 was subsequently used as a substrate for the bioconversion by Ginkgo cell cultures, and the product obtained was confirmed to be the same as 2, which suggested that 2 is biosynthesized from 1. Investigation on properties of the related enzymes responsible for the biotransformation reaction through the experimental techniques of cell-free culture and substrate/product concentration analysis revealed that the enzymes were extracellular and constitutive.

The biotransformations of cinobufagin (1), an animal-originated bufadienolide, by cell suspension cultures of Catharanthus roseus and Platycodon grandiflorum were investigated. Incubation for 6 days of 1 with C. roseus yielded four products, desacetylcinobufotalin (2), 3-epi-desacetylcinobufagin (3), 1β-hydroxyl desacetylcinobufagin (4) and 3-epi-desacetylcinobufotalin (5), among which 4 is a new compound. Time course investigation revealed that the biotransformation rates of two major products, 2 and 3, reached their highest levels of 44.7 and 16.5%, respectively, on the third day after substrate administration. Compounds 2-5 showed more potent cytotoxic activities against HL-60 cell lines than the parent compound 1. A plausible biotransformation pathway is proposed to account for the formation of the observed products. From the culture supernatant of P. grandiflorum, 2 was isolated in 37.8% yield after 8 days of incubation with 1. Cinobufotalin (6) and desacetylcinobufagin (7) were also obtained as minor products. The two plant suspension cultures exhibited similar transformation patterns on compound 1.

Catharanthus roseus cell suspension cultures were used to bioconvert both triptolide (1) and triptonide (2). The same reaction path was followed in both biotransformations. Two biotransformed products were obtained and their structures identified as triptriolide (3) and 12β, 13α-dihydroxytriptonide (4), respectively, from 1 and 2. Product 4 is a new compound.

The diterpenoid triepoxides are the major active constituents of Tripterygium wilfordii with potent antitumor and immune activities. But the strong toxicity of these compounds has restricted their application to a great extent. In order to find more effective compounds with less toxicity, structural modifications of triptonide (1) by Aspergillus niger (AS 3.739) were investigated and four biotransformed products were obtained. Based on their chemical and spectral data, their structures were elucidated as 5αhydroxytriptonide (2), triptolide (3), 17-hydroxytriptonide (4), and 16-hydroxytriptonide (5), among which 2, 4 and 5 are new compounds. All the three new transformed products showed cytotoxic activities against the majority of the human tumor cell lines tested, however, they are found to possess less cytotoxic activity when compared with 1. Both compounds 4 and 5 showed similar cytotoxic activity and their IC50 values were 5-15 fold less than 1, while 2 is about 100 times less active than 1.

Directional modifications of resibufogenin 1 by Mucor subtilissimus and Pseudomonas aeruginosa were carried out. The substrate was hydroxylated at C-12 by M. subtilissimus AS 3.2454, from which a major product 12-hydroxyresibufogenin 2 was obtained. Then product 2 was dehydrogenated by P. aeruginosa AS 1.860, which resulted in a new compound 12β-hydroxy-3-keto-resibufogenin 3.