We evaluated a number of terthiophenes and polyynes, from the Asteraceae, for biological activities against microorganisms, viruses, and tumor cells, with and without the aid of UVA (long wavelength ultraviolet) radiation. The terthiophenes, which represented the basic alpha-terthienyl nucleus with simple side chains, showed impressive UVA-dependent activities, some of which were superior to alpha-terthienyl itself. In contrast, the polyynes had no significant biological activity, with or without UVA. We believe that these terthiophenes would be worthwhile evaluating in animal models of infectious diseases.