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Marine environment has demonstrated to be an interesting source of compounds with uncommon and unique chemical features on which the molecular modeling and chemical synthesis of new drugs can be based with greater efficacy and specificity for the therapeutics. Cancer is a growing public health threat, and despite the advances in biomedical research and technology, there is an urgent need for the development of new anticancer drugs. In this field, it is estimated that more than 60% of commercially available anticancer drugs are natural biomimetic inspired. Among the marine organisms, algae have revealed to be one of the major sources of new compounds of marine origin, including those exhibiting antitumor and cytotoxic potential. These compounds demonstrated ability to mediate specific inhibitory activities on a number of key cellular processes, including apoptosis pathways, angiogenesis, migration and invasion, in both in vitro and in vivo models, revealing their potential to be used as anticancer drugs. This review will focus on the bioactive molecules from algae with antitumor potential, from their origin to their potential uses, with special emphasis to the alga Sphaerococcus coronopifolius as a producer of cytotoxic compounds.

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Aims: This study attempts to establish a relationship between the Cr(VI) resistance of the culturable microbial community and the Cr(VI) resistance and Cr(VI)‐reducing ability of representative strains of each population, in order to assess whether these are exclusive characteristics of one microbial group or abilities shared among many groups. Methods and Results: A group of 48 Cr(VI)‐resistant isolates, with different colony types, was isolated from chromium‐contaminated activated sludge. Sodium dodecyl sulphate‐polyacrylamide gel electrophoresis protein patterns and fatty acid methyl ester analysis identified six populations, representing 54% of the isolated bacteria, as belonging to the genera Acinetobacter and Ochrobactrum. The remaining populations included strains identified as species of the β‐Proteobacteria and high G + C Gram‐positive bacteria. The Cr(VI) resistance and reduction ability of the strains were tested. All but two isolates grew in the presence of 1 mmol l−1 Cr(VI). During enrichment, all isolates were able to survive to 2 mmol l−1 Cr(VI) and complete Cr(VI) reduction was achieved. Representative strains of each population were able to partially reduce (5·4–39·1%) the Cr(VI) present in the growth medium. Conclusions: Most of the identified isolates have never been reported to be Cr(VI)‐resistant and/or Cr(VI)‐reducing strains. The mechanisms of Cr(VI) resistance and reduction may differ from group to group; therefore, it is evident that both Cr(VI) resistance and reduction are shared abilities and not an exclusive characteristic of a single group, possibly reflecting horizontal genetic transfer resulting from selective pressure in this contaminated environment. Significance and Impact of the Study: To our knowledge, this is the first study of a microbial community under chronic chromate stress and, as the success of microbial‐based metal remediation technologies requires a better understanding of the microbial community and the population response to metal stress, it may contribute to the implementation of a strategy of bioremediation of chromate‐contaminated environments.

For over a century, chromium (Cr) has found widespread industrial and commercial use, namely as a pigment, in the production of stainless steel and in chrome plating. The adverse health effects to the skin and respiratory tract of prolonged exposure to Cr have been known or suspected for a long time, but it was much more recently that the toxicity of this element was unequivocally attributed to its hexavalent state. Based on the combined results of extensive epidemiological studies, animal carcinogenicity studies and several types of other relevant data, authoritative regulatory agencies have found sufficient evidence to classify hexavalent chromium [Cr(VI)] compounds as encountered in the chromate production, chromate pigment production and chromium plating industries as carcinogenic to humans. Crucial for the development of novel strategies to prevent, detect and/or treat Cr(VI)-induced cancers is a detailed knowledge of the molecular and cellular mechanisms underlying these pathologies. Unfortunately, in spite of a considerable research effort, crucial facets of these mechanisms remain essentially unknown. This review is intended to provide a concise, integrated and critical perspective of the current state of knowledge concerning multiple aspects of Cr(VI) carcinogenesis. It will present recent theories of Cr(VI)-induced carcinogenesis and will include aspects not traditionally covered in other reviews, such as the possible involvement of the energy metabolism in this process. A brief discussion on the models that have been used in the studies of Cr(VI)-induced carcinogenicity will also be included, due to the impact of this parameter on the relevance of the results obtained.

Bacterial strain 5bvl1, isolated from a chromium-contaminated wastewater treatment plant and identified as Ochrobactrum tritici, was resistant to a broad range of antibiotics, to Cr(VI), Ni(II), Co(II), Cd(II), and Zn(II), and was able to grow in the presence of 5% NaCl and within the pH range 4-10. Characterization showed that strain 5bvl1 could be considered a halotolerant and alkalitolerant microorganism resistant to high concentrations of Cr(VI). This strain was able to grow aerobically in up to 10 mmolxL(-1) Cr(VI). Cr(VI) resistance was independent of sulphate concentration. Under aerobic conditions strain 5bvl1 was also able to reduce high Cr(VI) concentrations (up to 1.7 mmolxL(-1)). Increasing concentrations of Cr(VI) in the medium lowered the growth rate of strain 5bv11 but the reduction in growth rate could not be directly correlated with the amount of Cr(VI) reduced. Unlike the type strain, which was only able to reduce Cr(VI), strain 5bvl1 was resistant to Cr(VI) and able to reduce it. Moreover, in strain 5bvl1, the rate and extent of Cr(VI)-reduction were higher than in the other strains of the genus Ochrobactrum. Ochrobactrum strain 5bvl1 resists high Cr(VI) concentrations and has a high Cr(VI)-reducing ability, making it a valuable tool in bioremediation.

A series of triaza macrocyclic tricarboxylate ligands with ring sizes of nine to twelve (NOTA, DETA, UNTA and DOTRA) have been synthesized. Their acid-base properties and protonation sequence have been established and compared with those of the corresponding cyclic triamines and trimethyl cyclic triamines, using potentiometric measurements and l H N M R pH titrations. The first protonation constant of the carboxylate ligands is very high, and larger than the value for the parent cyclic amines. It is also very sensitive to the presence of Na' ions in solution. The first t w o protonation constants correspond to protonation of the ring nitrogens, and their increase with ring size is non-monotonic, reflecting p H-dependent conformational effects. These effects, due to electrostatic interactions as well as to hydrogen bond formation, caused difficulties in the application of methods (previously used for noncyclic polyaminocarboxylates) to obtain the protonation sequence from the 'H NM R p H titrations, similar to a previous occurrence for tetraaza macrocycles. By studying the p H dependence of the shielding parameters, C, and C,,, the protonation sequences were then obtained. For each of the four compounds studied, two nitrogen atoms are protonated before the carboxylate groups. Formation of hydrogen bonds between protonated nitrogens and non-protonated carboxylates affects the basicity of the latter, reducing the flexibility of these ligands in certain p H intervals.

The protonation constants of the macrocyclic ligand 1,4,7-triazacyclononane-N,N',N"-triacetic acid (NOTA) have been measured by potentiometry, and the protonation sequence of the various amino and carboxylate groups of NOTA has been studied in DzO as a function of pD from the chemical shifts of the nonlabile protons. Shielding constants for protonation of the amino groups were determined in a NMR study of the triaza macrocyclic amine, its trimethylated analogue, and NOTA and compared with values reported for linear polyamino polycarboxylates and cyclic tetraaza tetracarboxylate ligands. The results indicate that two nitrogens of NOTA are protonated at higher pH than the carboxylate groups. The last nitrogen is protonated only at very low pH. The sequence of protonation of NOTA supports the formation of hydrogen bonds between two protonated nitrogens and the adjacent two nonprotonated carboxylates. The 'H and I3C spectra of the La(N0TA) and Lu(N0TA) species were studied as a function of pH and temperature. The aqueous complexes show spectra characteristic of flexible triaza macrocycles, displaying fast interconversion between the two staggered 6 and X conformations of the ethylenediamine rings even at room temperature. Above pH 9.5, the La(N0TA) and Lu(N0TA) hydroxo complexes start to form and their spectra show evidence of greater rigidity as at room temperature the 6/X ethylenediamine ring conformational interconversions in the Lu(N0TA) hydroxo complex are slow on the NMR time scale.Current interest in the complexation properties of macrocycles showing remarkable cation-binding selectivity' has led to the synthesis and study of a large number of new macrocycles derived from cyclic polyaza and cyclic polyaza polyoxa ligands with ionizable functions such as @-diketonate,z d i p h e n o l~,~ or carboxylate groups.e7 Some of these macrocycles should be very useful as models of certain biological systems and as possible reagents for complexometric titrations. Increased selectivity to cation complexation should also be achieved by these ligands because of the combined effects of internal cavity size, rigidity, and nature of donor atoms and of pH-selective coordinating groups.The purpose of the present work is twofold. First, the protonation constants and the protonation scheme of the macrocyclic triaza ligand 1,4,7-triazacyclononane-N,N',N''-triacetic acid (1, NOTA) were obtained with use of potentiometric titrations and IH NMR pH titrations. To help interpret the NOTA NMR results, we also studied the cyclic triamine 2 and the N-methylated triaza macrocycle 3. The protonation shifts measured for these cyclic amines were used in a quantitative study of the proton distribution at the various basic sites of NOTA. The conclusions obtained for NOTA were compared with results for noncyclic polyamino polyacetic acidss-10 and for the cyclic tetraaza ligands 1,4~7,10-tetraazacyclododecane-N,N',N'',N"'-tetraacetic acid (DOTA) and 1,4,8,11 -tetraazacyclotetradecane-N,N',N'',N"'-tetraacetic acid (TETA).6,7-'1 The quantitative ...