Recent advances in metal-mediated nitrogen oxyanion reduction using reductively borylated and silylated N-heterocycles

The reduction of nitrogen oxyanions is critical for the remediation of eutrophication caused by anthropogenic perturbations to the natural nitrogen cycle. There are many approaches to nitrogen oxyanion reduction, and here we report our advances in reductive deoxygenation using pre-reduced N-heterocycles. We show examples of nitrogen oxyanion reduction using Cr, Fe, Co, Ni, and Zn, and we evaluate the role of metal choice, number of coordinated oxyanions, and ancillary ligands on the reductive transformations. We report the experimental challenges faced and provide an outlook on new directions to repurpose nitrogen oxyanions into value-added products.

Unprecedented Outbreak of Harmful Algae in Pacific Coastal Waters off Southeast Hokkaido, Japan, during Late Summer 2021 after Record-Breaking Marine Heatwaves

Unprecedented large-scale harmful algae blooms (HABs) were reported in coastal waters off the south-eastern coast of Hokkaido, Japan, in mid-to-late September 2021, about a month after very intense and extensive marine heatwaves subsided. To understand the physical–biological processes associated with development of the HABs, we conducted analyses via a combination of realistic ocean circulation models, particle-tracking simulations, and satellite measurements. The satellite-derived chlorophyll concentrations (SCCs) and areal extent of the high SCCs associated with the HABs were the highest recorded since 1998. More specifically, the extent of SCCs exceeding 5 or 10 mg m−3 started to slowly increase after 20 August, when the marine heatwaves subsided, intermittently exceeded the climatological daily maximum after late August, and reached record-breaking extremes in mid-to-late September. About 70% of the SCCs that exceeded 10 mg m−3 occurred in places where water depths were <300 m, i.e., coastal shelf waters. The high SCCs were also tightly linked with low-salinity water (e.g., subarctic Oyashio and river-influenced waters). High-salinity subtropical water (e.g., Soya Warm Current water) appeared to suppress the occurrence of HABs. The expansion of the area of high SCCs seemed to be synchronized with the deepening of surface mixed layer depths in subarctic waters on the Pacific shelves. That deepening began around 10 August, when the marine heatwaves weakened abruptly. However, another mechanism was needed to explain the intensification of the SCCs in very nearshore waters off southeast Hokkaido. Particle-tracking simulations based on ocean circulation models identified three potential source areas of the HABs: the Pacific Ocean east of the Kamchatka Peninsula, the Sea of Japan, and the Sea of Okhotsk east of the Sakhalin Island. Different processes of HAB development were proposed because distance, time, and probability for transport of harmful algae from the potential source areas to the study region differed greatly between the three source areas.

An Integrated View of Nitrogen Oxyanion Deoxygenation in Solution Chemistry and Electrospray Ion Production

There has been an increasing interest in chemistry involving nitrogen oxyanions, largely due to the environmental hazards associated with increased concentrations of these anions leading to eutrophication and aquatic "dead zones". Herein, we report the synthesis and characterization of a suite of MNO_x complexes (M = Co, Zn: x = 2, 3). Reductive deoxygenation of cobalt bis(nitrite) complexes with bis(boryl)pyrazine is faster for cobalt than previously reported nickel, and pendant O-bound nitrito ligand is still readily deoxygenated, despite potential implication of an isonitrosyl primary product. Deoxygenation of zinc oxyanion complexes is also facile, despite zinc being unable to stabilize a nitrosyl ligand, with liberation of nitric oxide and nitrous oxide, indicating N-N bond formation. X-ray photoelectron spectroscopy is effective for discriminating the types of nitrogen in these molecules. ESI mass spectrometry of a suite of M(NO_x)_y (x = 2, 3 and y = 1, 2) shows that the primary form of ionization is loss of an oxyanion ligand, which can be alleviated via the addition of tetrabutylammonium (TBA) as a nonintuitive cation pair for the neutral oxyanion complexes. We have shown these complexes to be subject to deoxygenation, and there is evidence for nitrogen oxyanion reduction in several cases in the ESI plume. The attractive force between cation and neutral is explored experimentally and computationally and attributed to hydrogen bonding of the nitrogen oxyanion ligands with ammonium α-CH₂ protons. One example of ESI-induced reductive dimerization is mimicked by bulk solution synthesis, and that product is characterized by X-ray diffraction to contain two Co(NO)₂⁺ groups linked by a highly conjugated diazapolyene.

A Redox-Active Tetrazine-Based Pincer Ligand for the Reduction of N-Oxyanions Using a Redox-Inert Metal

The reaction chemistry of the bis-tetrazinyl pyridine ligand (btzp) towards nitrogen oxyanions coordinated to zinc is studied in order to explore the reduction of the NO_x ^- substrates with a redox-active ligand in the absence of redox activity at the metal. Following syntheses and characterization of (btzp)ZnX₂ for X=Cl, NO₃ and NO₂ , featuring O-Zn linkage of both nitrogen oxyanions, it is shown that a silylating agent selectively delivers silyl substituents to tetrazine nitrogens, without reductive deoxygenation of NO_x ^-1 . A new synthesis of the highly hydrogenated H₄ btzp, containing two dihydrotetrazine reductants is described as is the synthesis and characterization of (H₄ btzp)ZnX₂ for X=Cl and NO₃ , both of which show considerable hydrogen bonding potential of the dihydrotetrazine ring NH groups. The (H₄ btzp)ZnCl₂ complex does not bind zinc in the pincer pocket, but instead H₄ btzp becomes a bridge between neighboring atoms through tetrazine nitrogen atoms, forming a polymeric chain. The reaction of AgNO₂ with (H₄ btzp)ZnCl₂ is shown to proceed with fast nitrite deoxygenation, yielding water and free NO. Half of the H₄ btzp reducing equivalents form Ag⁰ and thus the chloride ligand remains coordinated to the zinc metal center to yield (btzp)ZnCl₂ . To compare with AgNO₂ , experiments of (H₄ btzp)ZnCl₂ with NaNO₂ result in salt metathesis between chloride and nitrite, highlighting the importance of a redox-active cation in the reduction of nitrite to NO.

Estimation of nitrogen and phosphorus concentrations from water quality surrogates using machine learning in the Tri An Reservoir, Vietnam

Surface water eutrophication due to excessive nutrients has become a major environmental problem around the world in the past few decades. Among these nutrients, nitrogen and phosphorus are two of the most important harmful cyanobacterial bloom (HCB) drivers. A reliable prediction of these parameters, therefore, is necessary for the management of rivers, lakes, and reservoirs. The aim of this study is to test the suitability of the powerful machine learning (ML) algorithm, random forest (RF), to provide information on water quality parameters for the Tri An Reservoir (TAR). Three species of nitrogen and phosphorus, including nitrite (N-NO₂^-), nitrate (N-NO₃^-), and phosphate (P-PO₄^3-), were empirically estimated using the field observation dataset (2009-2014) of six surrogates of total suspended solids (TSS), total dissolved solids (TDS), turbidity, electrical conductivity (EC), chemical oxygen demand (COD), and biochemical oxygen demand (BOD₅). Field data measurement showed that water quality in the TAR was eutrophic with an up-trend of N-NO₃^- and P-PO₄^3- during the study period. The RF regression model was reliable for N-NO₂^-, N-NO₃^-, and P-PO₄^3- prediction with a high R² of 0.812-0.844 for the training phase (2009-2012) and 0.888-0.903 for the validation phase (2013-2014). The results of land use and land cover change (LUCC) revealed that deforestation and shifting agriculture in the upper region of the basin were the major factors increasing nutrient loading in the TAR. Among the meteorological parameters, rainfall pattern was found to be one of the most influential factors in eutrophication, followed by average sunshine hour. Our results are expected to provide an advanced assessment tool for predicting nutrient loading and for giving an early warning of HCB in the TAR.

Concerns and Threats of Contamination on Aquatic Ecosystems

Aquatic ecosystems are the ultimate sinks for the contaminants. Water contamination is the outcome of human activities such as urbanization, industrialization, and agricultural activities. The overuse of pesticides and fertilizers and sewage from residential and industrial areas ultimately find its way to aquatic environment. Thus results in the degradation of the water quality and leads to the spread of infectious diseases such as dysentery, diarrhea, and jaundice. Contamination in aquatic environs is one of the leading types of pollution which has significant negative health issues and mortality. Water has a natural capacity to neutralize the contamination, but when contamination becomes uncontrolled, water will lose its self-generating capacity. Therefore, there is a need for regular monitoring and controlling of pollutant discharge into the nearby aquatic environs.

Quantification of the Cost and Potential Environmental Effects of Unused Pharmaceutical Products in Cataract Surgery

Importance

Pharmaceutical products, including unused portions, may contribute to financial and environmental costs in the United States. Because cataract surgery is performed millions of times each year in the United States and throughout the rest of the world, understanding these financial and environmental costs associated with cataract surgery is warranted.

Objective

To investigate the financial and environmental costs of unused pharmaceutical products after phacoemulsification surgery.

Design, Setting, and Participants

This descriptive qualitative study included 4 surgical sites in the northeastern United States (a private ambulatory care center, private tertiary care center, private outpatient center, and federally run medical center for veterans). Prices and data for use of services and pharmaceuticals were obtained for the tertiary care and outpatient centers from January 1 through April 30, 2016; for the ambulatory care center from June 1, 2017, through March 31, 2018; and the federal medical center from November 1, 2017, through February 28, 2018. Data were collected from routine phacoemulsification surgical procedures without vitreous loss or other complications. Volume or weight of medications remaining after surgery was measured. Total and mean costs of medications per case and month were calculated. Environmental effects were estimated using economic input-output life cycle assessment methods. Data were analyzed from December 1, 2017, through June 30, 2018.

Main Outcomes and Measures

Cost of unused pharmaceutical products (in US dollars) and kilogram equivalents of carbon emissions (carbon dioxide [CO2-e]), air pollution (fine particulate matter emissions of ≤10 μm in diameter [PM10-e]), and eutrophication potential (nitrogen [N-e]).

Results

A total of 116 unique drugs were surveyed among the 4 centers. Assuming unmeasured medications had no materials left unused, a cumulative mean 83 070 of 183 304 mL per month (45.3%) of pharmaceuticals were unused by weight or volume across all sites. Annual unused product cost estimates reached approximately $195 200 per site. A larger percentage of eyedrops (65.7% by volume) were unused compared with injections (24.8%) or systemic medications (59.9%). Monthly unused quantities at the ambulatory care center (65.9% by volume [54 971 of 83 440 mL]), tertiary care center (21.3% [17 143 of 80 344 mL]), federal medical center (38.5% [265 of 689 mL]), and outpatient center (56.8% [10 691 of 18 832 mL]) resulted in unnecessary potential emissions at each center of 2135, 2498, 418, and 711 kg CO2-e/mo, respectively. Unnecessary potential air pollution between sites varied from 0.8 to 4.5 kg PM10-e/mo, and unnecessary eutrophication potential between sites varied from 0.07 to 0.42 kg N-e/mo.

Conclusions and Relevance

This study suggests that unused pharmaceutical products during phacoemulsification result in relatively high financial and environmental costs. If these findings can be substantiated and shown to be generalizable in the United States or elsewhere, reducing these costs may be of value.

Using Geospatial Analysis and Hydrologic Modeling to Estimate Climate Change Impacts on Nitrogen Export: Case Study for a Forest and Pasture Dominated Watershed in North Carolina

Many watersheds are currently experiencing streamflow and water quality related problems that are caused by excess nitrogen. Given that weather is a major driver of nitrogen transport through watersheds, the objective of this study was to predict climate change impacts on streamflow and nitrogen export. A forest and pasture dominated watershed in North Carolina Piedmont region was used as the study area. A physically-based Soil and Water Assessment Tool (SWAT) model parameterized using geospatial data layers and spatially downscaled temperature and precipitation estimates from eight different General Circulation Models (GCMs) were used for this study. While temperature change predictions are fairly consistent across the GCMs for the study watershed, there is significant variability in precipitation change predictions across the GCMs, and this leads to uncertainty in the future conditions within the watershed. However, when the downscaled GCM projections were taken as a model ensemble, the results suggest that both high and low emission scenarios would result in an average increase in streamflow of 14.1% and 12.5%, respectively, and a decrease in the inorganic nitrogen export by 12.1% and 8.5%, respectively, by the end of the century. The results also show clear seasonal patterns with streamflow and nitrogen loading both increasing in fall and winter months by 97.8% and 50.8%, respectively, and decreasing by 20.2% and 35.5%, respectively, in spring and summer months by the end of the century.

Sixty Challenges – A 2030 Perspective on Natural Products and Medicines Security

Natural products matter, for they are essential contributors to societal well-being and global health. Flavors, fragrances, essential oils, traditional medicines and phytopharmaceuticals, and prescription and over-the-counter products all utilize constituent materials from natural sources. However, these vast natural resources of Earth are disappearing, and climate change and market expansion by a dramatically increasing and ageing population will continue to strain plant sourcing in the decades ahead. It was with these and other considerations that the term “ecopharmacognosy” was developed as both a philosophy and a practice, and from which the necessity for a “medicines security” strategy evolved.

Extending previous presentations, a series of sixty challenges for 2030 to the status quo promotes the discussion of a different vision for the natural product sciences as applied to traditional medicines. Among the topics presented are areas for global collaborative initiatives in science and in data management, the impact of climate change on medicinal plant accessibility, the sustainability and quality of the natural products that patients receive, and the integration of new technologies, particularly the genomics of secondary metabolite biosynthesis, hand-held detection systems and artificial intelligence, and the implications of increased life expectancy on future health care needs. The presentation closes with two examples of newer approaches in drug discovery.

Toxin-assisted micropredation: experimental evidence shows that contact micropredation rather than exotoxicity is the role of Prymnesium toxins

Blooms of Prymnesium parvum can severely harm fish and zooplankton, presumably through the release of allelopathic exotoxins that offer advantages for Prymnesium in its interactions with competitors and prey. We show that Prymnesium attaches to zooplankton and fish, causing mortality, whereas exposure of these organisms to Prymnesium across a permeable membrane does not cause mortality. We also show that Prymnesium exotoxins are released independently of contact toxicity only in response to experimental procedures or natural causes of stress. Our results are consistent with the idea that toxins have evolved for release during cell-to-cell contact in support of heterotrophy. The evolution of toxin-assisted micropredation would be consistent with mechanisms of natural selection favouring individual fitness as opposed to broadcast allelopathy from which the benefits are more dispersed. Research into the toxicity of Prymnesium and other harmful algal species may profit from focus on processes following physical contact with potential prey.

Evaluation of dietary assessment tools used to assess the diet of adults participating in the Communities Advancing the Studies of Tribal Nations Across the Lifespan cohort

BACKGROUND

Accurate assessment of dietary intake is essential for researchers and public health practitioners to make advancements in public health. This is especially important in Native Americans who display disease prevalence rates that are dramatically higher than the general US population.

OBJECTIVE

To evaluate three dietary assessment tools: dietary records, a food frequency questionnaire (FFQ), and a shellfish assessment survey among Native American adults from the Communities Advancing the Studies of Tribal Nations Across the Lifespan (CoASTAL) cohort.

DESIGN

The CoASTAL cohort was composed of randomly selected individuals from three tribal registries of Pacific Northwest Tribal Nations. This cross-sectional study used data from the baseline of CoASTAL and was restricted to the non-pregnant adults (aged 18 years or older) who completed the shellfish assessment survey (n=500), an FFQ (n=518), dietary records (n=444), weight measures (n=493), and height measures (n=496). Paired t tests, Pearson correlation coefficients, and percent agreement were used to evaluate the dietary records and the FFQ with and without accounting for plausibility of reported energy intake (rEI). Sensitivity and specificity as well as Spearman correlation coefficients were used to evaluate the shellfish assessment survey and the FFQ compared to dietary records.

RESULTS

Statistically significant correlations between the FFQ and dietary records for selected nutrients were not the same by sex. Accounting for plausibility of rEI for the dietary records and the FFQ improved the strength of the correlations for percent energy from protein, energy from carbohydrate, and calcium for both men and women. In addition, the association between rEI (dietary records and FFQ) and weight became significant when the sample was limited to plausible rEI. The shellfish assessment survey was found to similarly assess shellfish consumption in comparison to the FFQ.

CONCLUSIONS

These results support the benefit of multiple measures of diet, including regional and culturally specific surveys, especially among Native Americans. Accounting for plausibility of rEI may ensure more accurate estimations of dietary intakes.

Ciguatera fish poisoning in la Habana, Cuba: a study of local social-ecological resilience

Following the collapse of the Cuban economy in the early 1990s, epidemiologists in the Cuban Ministry of Health noticed dramatic increases in reported outbreaks of ciguatera fish poisoning (CFP) in some coastal communities. This article summarizes the results of a comparative case study which applied an ecosystem approach to human health to investigate this issue. Situated learning and complexity theories were used to interpret the results of the investigation. CFP outbreaks are influenced by a complex set of interactions between ecological and socioeconomic processes. This study found that the level of organization of the local sports fishing community and the degree of degradation of the local nearshore marine ecosystem appear to be key factors influencing the diverging levels of CFP outbreaks recorded in the 1990s in the communities studied.

Ciguatoxin-like substances in edible fish on the eastern Mediterranean

BACKGROUND

The consumption of edible fish (e.g., Siganus spp) was assumed to have caused ciguatera poisoning at an atypical site, the eastern Mediterranean. This pilot study assesses the presence of ciguatoxin-like substances in edible fish on the eastern Mediterranean coast of Israel.

METHODS

Samples of Siganus rivulatus from polluted seawater (Haifa Bay), Siganus rivulatus from relatively clean seawater (Dor), and fish from the freshwater Sea of Galilee not inhabited by toxic algae were analyzed during summertime. Ciguatoxin-like substances were tested by a membrane immunobead assay that yields a color reaction (positive, weakly positive, negative).

RESULTS

Significantly more large and small fish from Haifa Bay yielded positive color reactions compared to fish from Dor. Sea of Galilee fish gave no positive color reactions.

CONCLUSIONS

Our results suggest the presence of ciguatoxin-like substances in edible fish of the eastern Mediterranean. Additional analyses are needed to determine whether these substances are ciguatoxins or related polyethers.

Climate change and human health: present and future risks

There is near unanimous scientific consensus that greenhouse gas emissions generated by human activity will change Earth's climate. The recent (globally averaged) warming by 0.5 degrees C is partly attributable to such anthropogenic emissions. Climate change will affect human health in many ways-mostly adversely. Here, we summarise the epidemiological evidence of how climate variations and trends affect various health outcomes. We assess the little evidence there is that recent global warming has already affected some health outcomes. We review the published estimates of future health effects of climate change over coming decades. Research so far has mostly focused on thermal stress, extreme weather events, and infectious diseases, with some attention to estimates of future regional food yields and hunger prevalence. An emerging broader approach addresses a wider spectrum of health risks due to the social, demographic, and economic disruptions of climate change. Evidence and anticipation of adverse health effects will strengthen the case for pre-emptive policies, and will also guide priorities for planned adaptive strategies.