Steroidal glycosides from Yucca rostrata and Dracaena braunii and their cytotoxic and antimicrobial evaluation

Steroidal glycosides are known to possess a wide range of biological activities such as cytotoxicity and antimicrobial effects. To isolate more of these glycosides to get a better understanding at their structure/activity relationship, and to complete chemotaxonomic information, a cultivated Yucca rostrata was studied, along with a wild and a cultivated Dracaena braunii. Thirteen spiro- and furostan glycosides were isolated from those plants and their structure were elucidated using 1D and 2D NMR. Since they were already reported from other plant species, it allowed us to get an idea on which type of structure might be specific to which taxon. The compounds from D. braunii were tested for their antimicrobial activity against Candida albicans, C. glabrata and Staphylococcus aureus. Only compound 12 (CAS 39491-39-9) showed a weak activity on S. aureus with a MIC of 50 μg/mL. The compounds from Y. rostrata were tested for their cytotoxicity against a CT26 (murine colorectal carcinoma) cell line. The spirostan glycosides 4 (CAS 119459-80-2) and 5 (CAS 164592-97-6) showed an interesting activity with an IC₅₀ of 2.38 μM and 2.26 μM, respectively. Comparing the structures of the active versus the inactive ones, we were able to formulate some hypotheses regarding the structure/activity relationships, in accordance with the current literature.