Ernesto Fernández

Comparative determination of photodegradation kinetics of quinolones

Abstract The photostabilities of several quinolones have been determined using high performance thin layer chromatography. On irradiation with UVA (350 nm), the photostability decreases in the order: ciprofloxacin (CP)> norfloxacin (NF) > pipemidic acid (PA) > nalidixic acid (NA) > M-193324 > rosoxacin (RS) > oxolinic acid (OA). The photo- degradation process in all cases follows first-order kinetics. Furthermore, the quantum yield of fluorescence was determined for each quinolone; these values vary from 0.15 x 10 −2 to 5.15 x 10 −2 . The highest Φ f value corresponds to CP and NF. These results show that quinolones which possess a piperazine ring at the C-7 position (CP, NF, PA) are less photostable and more fluorescent.

EFFECTS OF SOLAR UV-B RADIATION IN THE ACCUMULATION OF RHIZOCARPIC ACID IN A LICHEN SPECIES FROM ALPINE ZONES OF CHILE

En la especie liquenica Acarospora schleicheri, recolectada en gradientes altitudinales a 18o, 19o y 33o Lat. S, en zonas alpinas de Chile, se determinaron y compararon las concentraciones de acido rizocarpico. Se observaron incrementos significativos en la acumulacion del metabolito con la altura s.n.m. y el aumento en los niveles de radiacion UV-B en los gradientes seleccionados. Los resultados obtenidos sugieren que la sintesis de acido rizocarpico es inducida por la radiacion UV-B y que su presencia representa una adaptacion quimica frente a los elevados niveles de radiacion UV-B en los habitats de esta especie liquenica.

Phototoxic potential of quinolones

The photohaemolytic potentials of the quinolones oxolinic acid, pipemidic acid, rosoxacin, norfloxacin, ciprofloxacin and M-193324 (synthesis intermediary) were evaluated and compared with the photohaemolysis induced by nalidixic acid. Quinolones with a piperazine group in position 7 (pipemidic acid, norfloxacin and ciprofloxacin) did not induce photohaemolysis. However, oxolinic acid, rosoxacin and M-193324 produced a concentration- and oxygen-dependent photohaemolysis. Ascorbic acid, histidine and thiourea inhibited the photohaemolysis induced by oxolinic acid, rosoxacin and M-193324, suggesting a photodynamic mechanism similar to that found with nalidixic acid. In addition, deuterium oxide increased the photohaemolysis induced by photohaemolytic quinolones, indicating that this process is mediated by singlet oxygen.

Effects of UV Radiation on Usnic Acid in Xanthoparmelia microspora (Müll. Arg. Hale)

An important decrease in the level of stratospheric ozone has been observed during the past decade (1), with accompanying increases in UV-B radiation (2) and some UV-A radiation (3), thus leading to probable damage to aquatic and terrestrial ecosystems (4–7). Inhabitants of terrestrial and aquatic ecosystems have developed strategies to cope with the potential stress induced by UV radiation. One of these strategies is the synthesis of photoprotector compounds derived mainly from the biosynthetic route of the polymalonate acetate (8–13). As levels of UV radiation increase, accumulation rates of some photoprotective compounds in lichen species from the Chilean Alpine zones also increase (14). Photodegradation of depsides may have accounted for the low levels of phenolics in lichens at higher elevations (15). It was observed that, in Xanthoparmelia lichens from the Alpine regions of Chile, the higher the altitude where the lichen was found, the greater amount of usnic acid it produced (16). This increase of usnic acid is the result of the lichen’s ability to adapt to radiation, which ensures its survival in extreme environmental conditions. In thalli from Xanthoparmelia oleosa collected at 4690 m no usnic acid was detected, which could be proof of the presence of a photodegradation product of usnic acid (17) but which has not been identified to date. In growth-chamber experiments lasting 1 week, thalli of Umbilicaria americana always produced smaller amounts of phenolic residue when exposed to both UV-B and UV-A radiation, compared with exposure to UV-A alone. In one field experiment exclusion of UV-B by light filtration produced significant increases in phenolic compounds. This increase occurs only during spring and autumn, when lichens are metabolically more active (18). In this article we evaluated the accumulation rates of usnic acid in Xanthoparmelia microspora (Mull. Arg. Hale) exposed to doses of solar radiation and to additional doses of UV-A and UV-B radiation. Furthermore, we report on the photolysis of usnic acid in nonnucleofilic solvents during exposure to higher doses of UV-A and UV-B radiation.

Evaluación de la respuesta antioxidante en Chiton granosus Frembly, 1928 (Mollusca: Polyplacophora) a contaminantes oxidativos

Oxidative stress is the damage at cellular, tissue or organic level produced by reactive oxygen species, that are produced as a result of the exposition to polluting agents, the ingestion through diet, UV radiation or to the oxygen metabolic processes. Chiton granosus is an intertidal organism abundant in Valparaiso, region of Chile. The objective of studying this species, by its abundance, is oriented to its use as biomarkers of oxidative polluting agents and so to evaluate its possible role as a monitoring species of the presence of these polluting agents. To evaluate, gonads, radular and digestive systems were analyzed from Chiton granosus collected from Torpederas, a highly polluted public sector, and Montemar (control area). Two hundreds and fifty nine individuals of Chiton granosus were collected; 133 from Torpederas and 126 from Montemar. The results indicate that no differences due to the sex exists in enzyme activity: catalase in the gonads, superoxide dismutase (SOD) in the radular and digestive systems. No influence of the sampling site was observed, nevertheless the lipoperoxidative damage was concordant with a greater oxidation level in females in the more polluted sector. Total antioxidant capacity exhibited significant differences due to sex and oxidative pollution.

Spectroscopic and photochemical properties of some annulated boldine derivatives

The aim of this study was to determine the influence of the substituent groups on the photostability of eight boldine derivatives, including some oxazole and oxazinone derivatives, in order to increase the sunscreen protection properties previously demonstrated for boldine. Such derivatives showed bands similar to those of boldine in the absorption and emission spectrum. The spectroscopic properties are pH dependent. The photostability of the derivative compounds was higher than that of boldine, in accordance with the low value of the photoconsumption quantum yield determined. The low fluorescence quantum yield values observed for boldine 1 and 4 as both base and hydrochloride derivative compounds led us to postulate that these compounds are deactivated by a mechanism different to the fluorescence pathway, probably due to the electron-withdrawing inductive effect of NO for boldine 1, and to the increase of the aromatic framework for boldine 4.

Phototoxicity induced by nalidixic and oxolinic acids: Decrease in cell survival of chick embryo fibroblasts and Hep-2 cells

The phototoxic effects of nalidixic and oxolinic acids were evaluated in two types of cultured cells: chick embryo fibroblast and Hep-2 (human laryngo carcinoma cell line). In order to evaluate the phototoxicity induced by nalidixic and oxolinic acids, both cell types were irradiated for 5 min in the presence of each drug. The results showed an inverse relationship between cell survival and the concentration of the drug added to the culture medium. The concentrations of nalidixic and oxolinic acids necessary to induce a phototoxic effect were in the range of therapeutic blood levels. Both chick embryo fibroblasts and Hep-2 cells were more sensitive to the phototoxic effect induced by nalidixic acid than oxolinic acid.