Alpha‐terthienyl, a Non‐photodynamic Phototoxic Compound

Abstract

Alpha-terthienyl (aT), a natural product first isolated in the plant Tagetes erecta (family Compositae), is the first member of a new class of phototoxic compounds, whose activity is not based on the generation of singlet oxygen. Its maximum activity against Candida utilis was at 370 nm, and was not affected by the presence of sodium azide. Furthermore, its phototoxicity against E. coli B cells was expressed under nitrogen, but not under oxygen. In the presence of UVA, radioactive aT formed covalent bonds with calf thymus DNA, and was also incorporated into the DNA of C. utilis. Two

The relationship between exposure to fragrance materials and persistent light reaction in the photosensitivity dermatitis with actinic reticuloid syndrome

“…The Candida test has been shown to be particularly effective for studying the phototoxicity of the psoralens and other substances which act against DNA (Daniels, 1965;Kagan et al, 1980). Where the Candida test is positive there is the possibility that a psoralen type of phototoxicity is present and this may be demonstrated in skin as an erythematous reaction with a prolonged latent period following a photopatch test.…”

“…Three in vitro methods were used to assess the phototoxic potential of these various fragrance materials. The first was the simple microbiological test described by Daniels (1965) but using Candida utilis rather than the pathogenic Candida albicans (Kagan, Gabriel & Reed, 1980) freshly seeded on Sabouraud's dextrose agar plates. Filter paper discs, saturated with fragrance material, or patch test materials in PMF, were placed on the surface of duplicate plates, one set being exposed to UV-A from a battery of four fiuorescent tubes (Thorn: Ultraviolet/non filter 2Q W; irradiance approximately 12 mW/cm^) for 48 h and the other set kept in the dark.…”

Comparison of the Antiviral Effects of Naturally Occurring Thiophenes and Polyacetylenes

“…The mechanism of action of ct-T is thought to be membrane damage resulting from oxygen dependent photoactivity (4,10,14,15,16). In contrast the mechanism underlying PHT phototoxicity is less clear (4,17,18). More recently, thiarubrine-A, a dithiacyclohexadiene polyacetylene occurring in a variety of Asteracae with documented medicinal histories (19)(20)(21)(22), was shown to possess toxic activity against certain bacteria and fungi, which was not light dependent but was augmented by UV-A, (23).…”

Superoxide dismutase in the anal gills of the mosquito larvae ofAedes aegypti: Its inhibition by α‐terthienyl

“…The toxic effects of a-terthienyl are multifarious. It includes the inactivation of a variety of enzymes including acetylcholinesterase in mosquito larvae [12], glucose-6-phosphate dehydrogenase and malate dehydrogenase [ll], the mediation of lipid peroxidation and thiol depletion [24], and the degradation of DNA and RNA [15]. The phototoxicity mediated damages are regarded to be a consequence of singlet oxygen production during photoactivation of a-terthienyl [ 11/25].…”

“…Treatment of a-terthienyl on some herbivorous insects shows sclerotization of pupae [13] and damage to the gut 1141. Many other biomolecules including RNA and DNA are targets of this naturally occurring thiophene in presence of long-wave UV light both in vivo and in vitro [15]. The toxicity of a-terthienyl increases when an organism treated with this compound is exposed to sunlight or long-wave ultraviolet light (320-400 nm) 1161.…”