Dihydrophenanthrofurans and bisbibenzyl derivatives from the stems of Dendrobium nobile.

Two new dihydrophenanthrofurans (1 and 2) and two new bisbibenzyl derivatives (3 and 4) were isolated from the traditional Chinese medicinal plant Dendrobium nobile, along with four known compounds (5-8). The absolute configurations of compounds 1 and 4 were elucidated through extensive NMR and ECD spectroscopic analyses. New compounds showed no antimicrobial activity against four gram-positive bacterial strains and four gram-negative bacteria at the concentration of 1 mg/mL, but displayed significant cytotoxic activity against HepG2 human hepatic cell line with the IC50 values ranging from 1.25 µM to 19.47 µM.

Biotransformation of ursolic acid by Syncephalastrum racemosum CGMCC 3.2500 and anti-HCV activity.

Microbial transformation of ursolic acid (UA, 3ß-hydroxy-urs-12-en-28-oic acid, 1) by filamentous fungus Syncephalastrum racemosum CGMCC 3.2500 was conducted. Five metabolites 3ß, 7ß, 21ß-trihydroxy-urs-12-en-28-oic acid (2); 3ß, 21ß-dihydroxy-urs-11-en-28-oic acid-13-lactone (3); 1ß, 3ß, 21ß-trihydroxy-urs-12-en-28-oic acid (4); 3ß, 7ß, 21ß-trihydroxy-urs-1-en-28-oic acid-13-lactone (5); and 21-oxo-1ß, 3ß-dihydroxy-urs-12-en-28-oic acid (6) were afforded. Elucidation of the structures of these metabolites was primarily based on 1D and 2D NMR and HR-MS data. Metabolite 2 was a new compound. In addition, the anti-HCV activity of compounds 1-6 was evaluated.

Biotransformation of ursolic acid by an endophytic fungus from medicinal plant Huperzia serrata.

Endophytic fungi were used not only for their producing bioactive products but also for their ability to transform natural compounds. An endophytic fungus, isolated from medicinal plant Huperzia serrata, was identified as Umbelopsis isabellina based on the internal transcribed spacer of ribosomal DNA (rDNA-ITS) region. It was used to transform ursolic acid (1), a pentacyclic triterpene. Incubation of ursolic acid with U. isabellina afforded three products, 3ß-hydroxy-urs-11-en-28,13-lactone (2), 3ß,7ß-dihydroxy-urs-11-en-28,13-lactone (3), 1ß,3ß-dihydroxy-urs-11-en-28,13-lactone (4). Although product 2 was a known compound, it was first obtained by microbial transformation. Products 3 and 4 were new compounds. The structural elucidation of the three compounds was achieved mainly by the 1D- and 2D-NMR, MS, IR data. The endophytic fungus U. isabellina can hydroxyate the C12-C13 double bond at position 13 of ursolic acid 1 and form a five-member lactone effectively. In the meantime, this fungus can also introduce the hydroxyl group at C-1 or C-7 of ursolic acid 1.

Multihydroxylation of ursolic acid by Pestalotiopsis microspora isolated from the medicinal plant Huperzia serrata.

The structural modification of ursolic acid by an endophytic fungus Pestalotiopsis microspora, isolated from medicinal plant Huperzia serrata was reported for the first time. The structure diversity was very important for the SAR study of ursolic acid and its derivatives. Incubation of ursolic acid 1 with P. microspora afforded four metabolites: 3-oxo-15α, 30-dihydroxy-urs-12-en-28-oic acid (2), 3ß, 15α-dihydroxy-urs-12-en-28-oic acid (3), 3ß, 15α, 30- trihydroxy-urs-12-en-28-oic acid (4) and 3,4-seco-ursan-4,30-dihydroxy-12-en-3,28-dioic acid (5). All products were new compounds and their structures elucidation was mainly based on the spectroscopic data.