Abstract:Cholesterol can be converted by Burkholderia cepacia into a series of steroid hormone prodrugs. A conversion product of cholesterol with higher medicinal value was identified as cholest-4-ene-3,6-dione by mass spectrometry, infrared spectrum and nuclear magnetic resonance spectroscopy, however, the hydrophobicity of cholesterol resulted in a relatively low conversion yield. Cyclodextrin was used to increase the conversion yield of the target product, and the effects of cyclodextrin on cell growth and substrate embedding were investigated. Multiple cyclodextrins were added to the conversion system and the molar ratio of methyl-β-cyclodextrin to cholesterol was 1∶1.The results showed that the molar conversion yield of cholest-4-ene-3,6-dione was significantly improved when methyl-β-cyclodextrin or hydroxyethyl-β-cyclodextrin was added, which was 27.55 times and 37.95 times higher than the control group, respectively. The addition ratio of hydroxyethyl-β-cyclodextrin and cholesterol was further optimized. And it was found that when the molar ratio of the two substances was 2∶1, the conversion yield of cholest-4-ene-3,6-dione was 1.59 times as high as that achieved at the molar ratio of 1∶1. Infrared spectroscopy was used to characterize the inclusion complexation of 2 mol hydroxyethyl-β-cyclodextrin with 1 mol substrate cholesterol. It was found that the A ring of the steroid nucleus, 26-C and 27-C of the side chain of cholesterol could be effectively wrapped by 2 mol of hydroxyethyl-β-cyclodextrin, respectively, to form a stable inclusion. Cholesterol could be effectively coated by hydroxyethyl-β-cyclodextrin, and the yield of cholester-4-ene-3,6-dione was improved, which could be used as a reference for the microbial transformation of cholest-4-ene-3,6-dione.
