Alexis St-Gelais
Université du Québec à Chicoutimi, Canada
Title: Dirchromones and dircoxepines, a new group of cytotoxic organic sulfur compounds from Dirca palustris (Thymelaeaceae)
Biography
Biography: Alexis St-Gelais
Abstract
Dirca palustris L. is a shrub that is endemic in the eastern part of North America, where it is commonly known as eastern leatherwood. It thrives under the canopy of the Canadian maple forests, and is the only native member of the Thymelaeaceae of the country. Its crushed bark was reportedly employed by the Iroquois to treat cancer. The plant also induces vomiting and vesication, and is a potent laxative. The highly cytotoxic dichloromethane extract from the ligneous parts of the plant was thus fractionated using a bioassay-guided strategy. Among other results, one of the active subfractions yielded several minority sulfur-containing compounds. They were characterized by NMR, HRMS, FTIR and UV spectroscopy, and named dirchromones and dircoxepines. Not only were they the first mention of organic sulfur compounds in the Thymelaeaceae, they also featured an original structure, unrelated to other known sulfur-bearing molecules in plants such as glucosinolates and cysteine-derived sulfoxides. The substitution pattern of dirchromones and the occurrence of dircoxepines can be explained by a common tentative metabolic relationship, although the origin of the parent compound remains unclear. Additionally, isolated dirchromones show a significant polarity-dependent cytotoxicity, with increasing activity and selectivity towards DLD-1 colorectal adenocarcinoma cells as the calculated logP increases.