Non-covalent interactions between thio-caffeine derivatives and water-soluble porphyrin in ethanol-water environment

Monitoring of caffeine concentration in infused tea, human urine, domestic wastewater and different water resources in southeast of Iran- caffeine an alternative indicator for contamination of human origin

The present study was developed to evaluate the caffeine concentration in commercially high-consumed brands of dry black tea, urine of tea consumers, raw and treated wastewater, as well as water resources (WRs) in Zabol city, Iran. Furthermore, a complementary analysis was performed to evaluate the relationship between caffeine content and total coliform (TCF) and Escherichia coli (E. coli) in water sources. In this end, tea (90 samples), urine (90 samples), raw sewage (72 samples), treated sewage (72 samples), and septic tank sewage (36samples) were taken from Zabol city and analyzed in terms of caffeine content. To evaluate the correlation between caffeine and TCF and E. coli, 102 water samples were taken from WRs in Zabol city. Caffeine was measured by high-performance liquid chromatography (HPLC). Furthermore, TFC and E. coli were measured based on the procedure outlined by standard methods for water and wastewater examination and the most probable number (MPN) method. The results indicated that the caffeine concentration in different tea brands consumed by Zabol people were in the range of 12.35-18.75 mg/L. The mean caffeine level in the male group' urine (7.08 ± 1.00 μg/mL) was significantly higher than the female group (4.83 ± 1.94 μg/mL). The results showed that the total average amount of caffeine in raw and treated wastewater in Zabol city was 21.04 ± 2.22 and 19.86 ± 2.08 μg/L, respectively. Besides, the caffeine removal efficiency by the Zabol wastewater treatment plant (ZWTP) was found to be between 4.79 and 51.39%. According to the results, the environmental risk associated with caffeine through the discharge of raw and treated wastewater from ZWTP into receiving WRs was estimated to be less than the allowable limit (RQ = 1). The results showed that caffeine could be an indicator for fecal contamination with human origin.

Comparative study of binding interactions between porphyrin systems and aromatic compounds of biological importance by multiple spectroscopic techniques: A review

The specific spectroscopic and redox properties of porphyrins predestine them to fulfill the role of sensors during interacting with different biologically active substances. Monitoring of binding interactions in the systems porphyrin-biologically active compound is a key question not only in the field of physiological functions of living organisms, but also in environmental protection, notably in the light of the rapidly growing drug consumption and concurrently the production of drug effluents. Not always beneficial action of drugs on natural porphyrin systems induces to further studies, with commercially available porphyrins as the model systems. Therefore the binding process between several water-soluble porphyrins and a series of biologically active compounds (e.g. caffeine, guanine, theophylline, theobromine, xanthine, uric acid) has been studied in different aqueous solutions analyzing their absorption and steady-state fluorescence spectra, the porphyrin fluorescence lifetimes and their quantum yields. The magnitude of the binding and fluorescence quenching constants values for particular quenchers decreases in a series: uric acid > guanine > caffeine > theophylline > theobromine > xanthine. In all the systems studied there are characters of static quenching, as a consequence of the π-π-stacked non-covalent and non-fluorescent complexes formation between porphyrins and interacting compounds, accompanied simultaneously by the additional specific binding interactions. The porphyrin fluorescence quenching can be explain by the photoinduced intermolecular electron transfer from aromatic compound to the center of the porphyrin molecule, playing the role of the binding site. Presented results can be valuable for designing of new fluorescent porphyrin chemosensors or monitoring of drug traces in aqueous solutions. The obtained outcomes have also the toxicological and medical importance, providing insight into the interactions of the water-soluble porphyrins with biologically active substances.