Chi-Kit Wat

Mosquito larvicidal activity of polyacetylenes from species in the Asteraceae

Twenty-four polyacetylenes isolated from species in the Asteraceae were screened for their near-UV-mediated larvicidal properties to the mosquito, Aedes aegypti. Dosage resonse lines for three of the most active compounds were prepared. One of these, σ-terthienyl from Tagetes was more toxic than DDT when near-UV radiation was provided. A scaled up trial with this compound in a simulated field situation demonstrated its potential as a larvicide. The effects of the radiation dose on larval survival were studied and the action spectra for the phototoxic effects of three compounds on larvae were obtained with narrowband interference filters. Because of the close agreement between the action and absorption spectra, it appears most probable that the polyacetylene is the primary absorbing compound. The potential of polyacetylenes as larvicides and their role in plant herbivore relations are discussed.

OXYGEN REQUIREMENT FOR NEAR-UV MEDIATED CYTOXICITY OF α-TERTHIENYL TO ESCHERICHIA COLI AND SACCHAROMYCES CEREVISIAE

Abstract— The photosensitizing activity of α‐terthienyl, a naturally occurring compound from Tagetes has been studied. Fluence‐response curves for the effect of α‐terthienyl and near‐UV radiation on Escherichia coli have been prepared. Photosensitization of E. coli was enhanced in aerobic as compared to anaerobic conditions and exogenous superoxide dismutase had a slight protective effect. Sodium azide, a quencher of 1O2, protected yeast cells from photosensitization with α‐terthienyl. The available evidence suggests that α‐terthienyl acts as a photodynamic sensitizer in vivo.

Photosensitization of invertebrates by natural polyacetylenes

Fourteen polyacetylenes or their thiophene derivatives, isolated from species in the Asteraceae were screened for their biological activity to mosquito larvae (Aedes aegypti), blackfly larvae (Simulium vittatum) and adult nematodes (Caenorhabditis elegans). Toxicity of the compounds was found to be enhanced greatly by irradiation with near-UV radiation or natural sunlight. Only wavelengths less than 400 nm were effective in promoting photosensitization. The results are discussed in relation to herbivore-plant interactions.

Phototoxic and antibiotic activities of plants of the asteraceae used in folk medicine

Ethanolic extracts of forty-four commercial herbal drugs and two fresh plants used in folk medicine, all species of the Asteraceae, were examined for their phototoxic and antibiotic activities against Escherichia coli, Saccharomyces cerevisiae and Candida albicans. Twenty samples were found to be active as either phototoxic and/or antibiotic agents and their phototoxic effects correlate with the presence of polyacetylenes and thiophenes.

Phototoxic polyacetylenes and their thiophene derivatives [Effects on human skin]

Polyacetylenes and their thiophene derivatives were tested for their effects on human skin. Topically applied α‐terthienyl evoked bi‐phasic phototoxic dermatitis and the appearance of ‘sunburn’ cells in human epidermis. None of 11 polyacetylenes had the same effect although they mimicked α‐terthienyl in their phototoxic effects on Candida albicans and certain pathogenic microorganisms. The UV‐mediated antibiotic activity of the compounds and their apparent lack of phototoxicity towards the skin suggest a potential topical therapeutic role for them in yeast, fungal and bacterial infections and light‐responsive dermatoses. Their topical sensitizing capacity, however, has not yet been studied.

Polyacetylenes in Hawaiian bidens

Abstract Leaves and roots of 19 species and six subspecies of Hawaiian Bidens were examined for polyacetylenes. Eleven C 13 hydrocarbons, aromatic and thiophenyl derivatives, one C 14 tetrahydropyran and three C 17 hydrocarbons were isolated all identified. All can be derived from a common precursor, oleic acid. Polyacetylenes were not detected in the leaves of 13 taxa although they are found in the roots of all. The occurrence of 2-[2-phenyl-ethyne-1-yl]-5 acetoxymethyl thiopene in Bidens has not been previously reported. Its ubiquitous presence is consistent with other evidence that the Hawaiian species are all derived from a single ancestral immigrant to the islands. Most taxa could be distinguished by their complement of polyacetylenes in roots and leaves. No variation was found to occur within taxa except in B. torta , in which each population had a unique array of polyacetylenes. Above the species level there appeared to be no taxonomically significant pattern to the distribution of polyacetylenes in this group.

Examination of naturally occurring polyacetylenes and α-terthienyl for their ability to induce cytogenetic damage

α-Terthienyl and 5 polyacetylenes were examined for chromosome damaging activity using Syrian hamster cells. None of these naturally occurring compounds induced sister chromatid exchanges and neither α-terthienyl nor phenylheptatriyne induced chromosome aberrations.

Photoinactivation of human erythrocyte enzymes by α-terthienyl and phenylheptatriyne, naturally occurring compounds in the asteraceae

In our laboratory, naturally occurring polyacetylenes and thiophene derivatives of the Asteraceae (Compositae) have been found to evoke antibiotic activities in light in the region 3 12-400 nm (UV-A) [l-5]. Phenylheptatriyne and cr-terthienyl are two examples of those compounds, which display lethal photosensitization towards various kinds of uniand muhicelhrlar organisms [3-61. The primary and major target of these photo-induced reactions has not been determined. Experiments with calf thymus DNA indicate that, unlike photoactive furano coumarins, PHT does not form interstrand crosslinkages with DNA in ultraviolet light [4]. Cell respiration of

Phenolic O-methyltransferase from Lentinus lepideus (basidiomycete)

Abstract The fungus, Lentinus lepideus, produces crystalline methyl p-methoxycinnamate in stationary cultures. O-methylation and methyl ester formation of hydroxycinnamic acids were examined with enzyme preparations of the fungus. Using S-adenosylmethionine-14CH3, it was found that only the methyl esters of the hydroxycinnamic acids are substrates for O-methylation and not the free acids. Benzoic acids and their methyl esters are not substrates. The activity of the enzyme is p-specific and its specific activity decreases with increasing number of hydroxyl groups in the substrate. The same enzyme preparations catalyze the formation of the methyl ester of cinnamic acid from the free acid.

Isolation and properties of hydroxycinnamate: CoA ligase from Polyporus hispidus

Abstract Hydroxycinnamate: CoA ligase was partially purified from the basidiomycete, Polyporus hispidus . The enzyme required ATP and CoA. Reduced activity was obtained with GTP. The same preparations catalyzed acetyl CoA formation. Light-grown cultures yielded preparations with an increased activity for hydroxycinnamic acids but not for acetate.