Polymer types and additive concentrations in single-use plastic products collected from Indonesia, Japan, Myanmar, and Thailand.

Marine debris comprising single-use plastic products (SUPs) is ubiquitous in Asian coastal waters, but there is little information on the types of polymers and the concentrations of plastic additives such waste products contain. In this study, 413 SUPs randomly collected from 4 Asian countries between 2020 and 2021 were analyzed to obtain specific polymer and organic additive profiles. Polyethylene (PE), coupled with external polymers, was prominent in the inside of the SUPs, whereas polypropylene (PP) and polyethylene terephthalate (PET) were prevalent in both the insides and outsides of the SUPs. The use of different polymers in the insides and outsides of PE SUPs implies specific and complicated recycling systems are required to maintain the purity of the products. Phthalate plasticizers including dimethyl phthalate (DMP), diethyl phthalate (DEP), diisobutyl phthalate (DiBP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP), and the antioxidant butylated hydroxytoluene (BHT) were prevalent in the SUPs (n = 68). High concentrations of DEHP were detected in PE bags from Myanmar (820,000 ng/g) and Indonesia (420,000 ng/g), which were an order of magnitude greater than the concentrations in PE bags collected in Japan. SUPs containing high concentrations of organic additives may be the primary source of harmful chemicals in the environment, and should be responsible for their ubiquitous distribution in ecosystems.

The biological activities of 5,15-diaryl-10,20-dihalogeno porphyrins for photodynamic therapy.

PURPOSE: Esophageal cancer is the most common gastrointestinal tumor and is difficult to be eradicated with conventional treatment. Porphyrin-based photosensitizers (PSs) mediated photodynamic therapy (PDT) could kill tumor cells with less damage to normal cells. As the most widely used porphyrin-based photosensitizer in clinics, Photofrin II has excellent anti-tumor effect. However, it has some disadvantages such as weak absorption at near infrared region, the complexity of components and prolonged skin photosensitivity. Here series novel 5,15-diaryl-10,20-dihalogeno porphyrin derivatives were afforded and evaluated to develop more effective and safer photosensitizers for tumor therapy. METHODS: The photophysical properties and singlet oxygen generation rates of 5,15-diaryl-10,20-dihalogeno porphyrins (I1-6, II1-4) were tested. The cytotoxicity of I1-6 and II1-4 were measured by MTT assay. The pathway of cell death was studied by flow cytometry. In vivo photodynamic efficacy of I3 and II2-4 in Eca-109 tumor-bearing BABL/c nude mice were measured and histopathological analysis were examined. RESULTS: 5,15-Diaryl-10,20-dihalogeno porphyrins I1-6 and II1-4 were synthesized. The longest absorption wavelength of these halogenated porphyrins (λmax = 660 nm) displayed a red shift around 30 nm compared to the unhalogenated porphyrins PS1 (λmax = 630 nm). The singlet oxygen generation rates of I1-6 and II1-4 were significantly higher than PS1 and HMME. All PSs mediated PDT showed obvious cytotoxic effect against Eca-109 cells compared to HMME in vitro and in vivo. Among these PSs, II4 exhibited appropriate absorption in the phototherapeutic window, higher 1O2 generation rate (k = 0.0061 s-1), the strongest phototoxicity (IC50 = 0.4 µM), lower dark toxicity, high generation of intracellular ROS in Eca-109 cells and excellent photodynamic anti-tumor efficacy in vivo. Besides, cell necrosis was induced by compound II4 mediated PDT. CONCLUSION: All new compounds have obvious photodynamic anti-esophageal cancer effects. Among them, the photosensitizer II4 showed excellent efficacy in vitro and in vivo, which has the potential to become a photodynamic anti-tumor drug.

Interactions of melatonin and its metabolites with the ABTS cation radical: extension of the radical scavenger cascade and formation of a novel class of oxidation products, C2-substituted 3-indolinones.

Melatonin had previously been shown to reduce up to four 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) cation radicals (ABTS*+) via a scavenger cascade ending with N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK). However, when melatonin is added to the reaction system in much lower quantities than ABTS*+, the number of radicals scavenged per melatonin molecule is considerably higher and can attain a value of ten. Under conditions allowing for such a stoichiometry, novel products have been detected which derive from AFMK (1). These were separated by repeated chromatography and the major compounds were characterized by spectroscopic methods, such as mass spectrometry (HPLC-MS, EI-MS and ESI-HRMS), 1H nuclear magnetic resonance (NMR) and 13C NMR, heteronuclear multiple bond connectivity (HMBC) correlations. The identified substances are formed by re-cyclization and represent 3-indolinones carrying the side chain at C2; the N-formyl group can be maintained, but deformylated analogs seem to be also generated, according to MS. The primary product from AFMK (1) is N-(1-formyl-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylidenemethyl)-acetamide (2), which is obtained after purification as E- and Z-isomers (2a, 2b); a secondary product has been identified as N-(1-formyl-2-hydroxy-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylmethyl)-acetamide (3). When H2O2 is added to the ABTS*+ reaction mixture in quantities not already leading to substantial reduction of this radical, compound 3 is isolated as the major product, whereas 2a and 2b are virtually absent. The substances formed differ from all previously known oxidation products which derive from melatonin and are, among these, the first 3-indolinones. Moreover, the aliphatic side chain at C2 is reminiscent of other substances which have been synthesized in the search for melatonin receptor ligands.

Reactions of the melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK) with the ABTS cation radical: identification of new oxidation products.

The melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK; 1), which was previously shown to be a potent radical scavenger, was oxidized using the ABTS cation radical [ABTS = 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)]. Several new oxidation products were obtained, which were separated by repeated chromatography and characterized by spectroscopic methods such as mass spectrometry (ESI-MS and ESI-HRMS), 1H-NMR and 13C-NMR, HMBC, HSQC, H,H COSY correlations and IR spectroscopy. The main products were oligomers of 1 (3 dimers, 1 trimer and 2 tetramers). In all cases, the amino group N2 was involved in the reactions. Two of the dimers turned out to be cis (2a) and trans (2b) isomers containing an azo bond. In the other dimer (3a), the nitrogen atom N2 was attached to atom C5 of the second aromatic amine, with loss of the methoxy group. In the trimer (5), one N2 formed a bridge to C5 of unit B, as in the respective dimer, while this one of C had bridged to C6 of B. One of the tetramers (6) was composed of a trimer 5 attached to N2 of a fourth 1 molecule via an azo bond as in 2a/b. In the other tetramer (7), an additional C-C bond between rings B and C in 6 is assumed. Although oligomers of AMK may only attain low in vivo concentrations, the types of reactions observed shed light on the physiologically possible metabolism of AMK once reacted with a free radical. The displacement of a methoxy group, rarely seen in the oxidation of methoxylated biomolecules, underlines the reactivity of AMK (1). Preliminary data show that, in the presence of ABTS cation radicals, AMK (1) can interact with side chains of aromatic amino acids, a finding which may be crucial for understanding to date unidentified protein modification by a melatonin metabolite detected earlier in experiments with radioactively labeled melatonin.