Metabolites identification of glycycoumarin, a major bioactive coumarin from licorice in rats.

Glycycoumarin is a major bioactive coumarin of licorice (Glycyrrhiza uralensis), one of the most popular herbal medicines worldwide. In this work, the metabolism of glycycoumarin in rats was investigated. After oral administration of 40mg/kg glycycoumarin, 4 and 10 metabolites were respectively detected in rats plasma and urine samples by liquid chromatography coupled with mass spectrometry (LC/MS). These metabolites were tentatively characterized by analyzing their tandem mass spectra and high-resolution mass spectra, and the structures of glucuronides were confirmed by ß-glucuronidase hydrolysis. Glycycoumarin mainly undertakes hydroxylation and glucuronidation metabolism, accompanied by hydrogenation and dehydrogenation as minor reactions. Two hydroxylated metabolites, 4''-hydroxyl glycycoumarin and 5''-hydroxyl glycycoumarin, were obtained by microbial transformation of Syncephalastrum racemosum AS 3.264, and their structures were fully identified by 1D and 2D NMR. Both metabolites are new compounds. Furthermore, they were proved to be catalyzed by P450 enzymes by rat liver microsomes incubation experiments. Finally, a metabolic pathway of glycycoumarin in rats was proposed. This is the first systematic study on metabolites identification of glycycoumarin.

Smith degradation, an efficient method for the preparation of cycloastragenol from astragaloside IV.

Cycloastragenol (CA) is the genuine sapogenin of astragaloside IV (ASI). This study focuses on the preparation of CA from ASI. Five hydrolysis methods were compared including H2SO4 hydrolysis, HCl hydrolysis, two-phase acid hydrolysis, mild acid hydrolysis, and Smith degradation. Seven hydrolysis products were purified, and five of them were identified as new compounds. The results indicated that Smith degradation was the most effective approach to prepare CA. In contrast, mild acid hydrolysis produced CA at a low yield, accompanied with the artificial sapogenin astragenol. The other three acid hydrolysis methods mainly produced astragenol. Furthermore, the reaction conditions for Smith degradation were optimized as follows: ASI was dissolved in 60% MeOH-H2O solution, oxidized with 5 equiv. NaIO4 for 12h, followed by reduction with 3 equiv. NaBH4 for 4h, and finally acidified with 1M H2SO4 at pH2 for 24h. Under the optimal conditions, CA could be prepared from ASI at a yield of 84.4%.

Microbial transformation of ursolic acid by Syncephalastrum racemosum (Cohn) Schroter AS 3.264.

Biotransformation of ursolic acid by the filamentous fungus Syncephalastrum racemosum (Cohn) Schroter AS 3.264 yielded five metabolites. Their structures were identified as 3ß,21ß-dihydroxy-urs-11-en-28-oic acid-13-lactone, 3ß,7ß,21ß-trihydroxy-urs-11-en-28-oic acid-13-lactone, 1ß,3ß-dihydroxy-urs-12-en-21-one-28-oic acid, 1ß,3ß,21ß-trihydroxy-urs-12-en-28-oic acid and 11,26-epoxy-3ß,21ß-dihydroxy-urs-12-en-28-oic acid based on NMR and MS spectroscopic analyses. The condensation reactions to form 28-oic acid-13-lactone ring and 11,26-epoxy ring are not frequently seen for the biotransformation of triterpenoids. One compound showed moderate inhibitory activity against protein tyrosine phosphatase 1B (PTP1B).