Degradation of methyl orange using short-wavelength UV irradiation with oxygen microbubbles.

A novel wastewater treatment technique using 8 W low-pressure mercury lamps in the presence of uniform-sized microbubbles (diameter = 5.79 microm) was investigated for the decomposition of methyl orange as a model compound in aqueous solution. Photodegradation experiments were conducted with a BLB black light blue lamp (365 nm), a UV-C germicidal lamp (254 nm) and an ozone lamp (185 nm+254 nm) both with and without oxygen microbubbles. The results show that the oxygen microbubbles accelerated the decolorization rate of methyl orange under 185+254 nm irradiation. In contrast, the microbubbles under 365 and 254 nm irradiation were unaffected on the decolorization of methyl orange. It was found that the pseudo-zero order decolorization reaction constant in microbubble system is 2.1 times higher than that in conventional large bubble system. Total organic carbon (TOC) reduction rate of methyl orange was greatly enhanced by oxygen microbubble under 185+254 nm irradiation, however, TOC reduction rate by nitrogen microbubble was much slower than that with 185+254 nm irradiation only. Possible reaction mechanisms for the decolorization and mineralization of methyl orange both with oxygen and nitrogen mirobubbles were proposed in this study.

Pyridinium cationic-dimer antimalarials, unlike chloroquine, act selectively between the schizont stage and the ring stage of Plasmodium falciparum.

Malaria is a leading cause of death in developing countries, and the emergence of strains resistant to the main therapeutic agent, chloroquine, has become a serious problem. We have developed cationic-dimer type antimalarials, MAP-610 and PMAP-H10, which are structurally different from chloroquine. In this study, we introduced several substituents on the terminal phenyl rings of PMAP-H10. The electronic and hydrophobic properties of the substituents were correlated with the antimalarial activity and cytotoxicity of the compounds, respectively. Studies with synchronized cultures of malarial plasmodia showed that our cationic-dimers act selectively between the schizont stage and the ring stage of the parasitic cycle, unlike chloroquine, which has a stage-independent action. Thus, the mechanism of action of our antimalarials appears to be different from that of chloroquine, and our compounds may be effective against chloroquine-resistant strains.

Antimalarial cation-dimers synthesized in two steps from an inexpensive starting material, isonicotinic acid.

Malaria is one of the three major serious infectious diseases in the world. As the area affected by malaria includes a large proportion of developing countries, there is a need for new antimalarials that can be synthesized and supplied inexpensively. To generate low-cost antimalarials, the MAP series 6-10, bis-cation dimers, synthesized by amidating the carboxyl group of isonicotinic acid (11) with various amines and by cationizing the nitrogen atoms of the pyridine ring with the corresponding alkyl bromides, were designed. This design enabled expansion of the structural variations of bis-cation-type antimalarial compounds. The compounds bearing alkyl or phenyl groups in the amide moieties showed remarkable antimalarial activities in vitro. Moreover, 1,1'-(1,12-dodecanediyl)bis[4-[(buthylamino)carbonyl]pyridinium bromide], MAP-412 (6 d), exhibited a potent antimalarial activity (ED(50)=8.2 mg kg(-1)). Being prepared at low cost, our bis-cation-type antimalarial compounds may be useful as lead compounds for inexpensive antimalarials.

Antimalarial effect of bis-pyridinium salts, N,N'-hexamethylenebis(4-carbamoyl-1-alkylpyridinium bromide).

The in vitro antimalarial activity of bis-pyridinium salts, N,N'-hexamethylenebis(4-carbamoyl-1-decylpyridinium bromide) and their derivatives, against the Plasmodium falciparum FCR-3 strain (ATCC 30932, chloroquine-sensitive) was evaluated. All test compounds exhibited antimalarial activity over a concentration range of 3.5microM to 10nM. The chain length of the N1-alkyl moiety was found to be very beneficial in terms of antimalarial activity, and in this series of compounds, the most appropriate N1-alkyl chain length was found to be eight.