A Study On Microbial Transformation Of Cyperenoic Acid By Cunninghamella Elegans AS 3.2028

Cyperenoic acid is one of the major bioactive sesquiterpenes of Croton crassifolius.Previous pharmacological studies had revealed that 1 shows potent anti-angiogenic property.However,its further development has been seriously restricted by the low polarity,poor water solubility,and difficult structural modification by chemical technology.In recent years,biotransformation is an effective tool in modification of natural products with potent bioactivities,and numerous microbial transformation metabolites have been reported.In order to overcome these difficulties and obtain structurally diverse derivations,microbial transformation of cyperenoic acid by using Cunninghamella elegans AS 3.2028 was studied.In this paper,a white crystal was isolated from C.crassifolius and its structure was identified based on various spectroscopic analyses,including HR-ESI-MS,NMR,experimental and calculated ECD spectroscopy.The crystal was finally identified as cyperenoic acid(1).The filamentous fungus transformation of 1 by C.elegans AS 3.2028 was carried out.Five new metabolites were isolated,and their structures were elucidated by HR-ESI-MS,NMR analysis and CD spectroscopy.They were identified as 7S-hydroxy-cyperenoic acid(2),8S-hydroxy-cyperenoic acid(3),9R-hydroxy-cyperenoic acid(4),10S-hydroxy-cyperenoic acid(5),and(11R)-12-hydroxy-cyperenoic acid(6).Compound 1-6 were tested for cell grown inhibition activity towards two types of human cancer cells by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide(MTT)assay using 5-fluorouracil(5-Fu)as a positive control.Compound 1 and its hydroxylated modification products 2-6(at five different concentrations from 12.5 μM to 200 μM)didn’t show significantly inhibition effect on HepG2 and MCF-7 cells,which means compounds 1-6 could not have obvious cytotoxicity activity.The potential anti-angiogenic activities of all biotransformation metabolites were evaluated by enzyme-linked immunosorbent assay(ELISA)in human cancer cell lines.Compared with cyperenoic acid(1),it was found that the biotransformation products 2 and 4 showed higher anti-angiogenic activities on HepG2 cells,and biotransformation product 3 showed higher anti-angiogenic activities on MCF-7 cells.