ABSTRACT
More than 700 polyacetylenes have been characterized, and they are particularly prominent in the Compositae, Umbelliferae and Campanulaceae, including many medicinal plants from various parts of the world. The thiophenes, and related sulfur-containing compounds such as dithiacyclohexadienes, are usually grouped together with the polyacetylenes because of their common biosynthetic pathways. Many of these thiophenes are also widely distributed in the plant kingdom and are often photosensitizers in the UVA region. The mechanism of action of thiophenes is better understood than it is for polyacetylenes. In contrast to the thiophenes, phenylheptatriyne and a number of other acetylenes appear to display a relatively complicated mode of action. There is a wide variation in the antiviral activities of different polyacetylenes and thiophenes, which appear to be determined primarily by their chemical structures. The most potent compounds contain two or more thiophene rings, which must however retain the optimum configuration for good antiviral activity.
