Steroids are natural compounds with several important applications in many fields of research, such as
medicinal chemistry, pharmacology, supramolecular chemistry and nanotechnology.In particular, bile
acids such as lithocholic acid (LCA) and ursodeoxycholic acid (UDCA) have been considered quite useful as
starting points for a rich and different set of medicinal chemistry activities.
Besides, the discovery of bioactive ingredients from plants and fungi is always the main target in medicinal
chemistry. The lanostane-type triterpenoid 3b-hydroxylanosta-8,24-diene-21-oic acid (Trametenolic acid,
TMA) was the main bioactive component of Gloeophyllum odoratum, which was reported to possess widely
bioactivities, including tumor cell anti-proliferation effects (for example, human HL-60 leukemia, human KB
epidermoid carcinoma, murine L1210 leukemia cells, Caski, HT-3, T-24, etc.), inhibition of enzyme activity
(human thrombin, bovine trypsin and so on).Nevertheless, trametenolic acid was scarcely investigated as
antimicrobial agent.
Structurally, bile acids (LCA and UDCA) and trametenolic acid are similar since they may be regarded as
consisting of two components, a rigid steroid nucleus and an aliphatic side chain possessing a carboxyl
group. On the basis of these considerations, six new compounds bearing a guanidine moiety in their side
chain were synthesized using LCA, UDCA and TMA as starting materials. The parent bile acids,
TMA and their resulting derivatives were evaluated for antimicrobial activity against S. aureus, B. subtilis
and M. smegmatis. The derivative 3a-hydroxy-23-guanidino-5b-cholane showed the best activity, with MIC
values of 12.5 μM against S. aureus, 5 μM against B. subtilis and 50 μM against M. smegmatis. The cytotoxic
activity of bile acids, trametenolic acid and derivatives was also evaluated against HT-29 cell line
