Application of a specific and sensitive radiometric assay for microbial lipase activities in marine water samples from the lagoon of nouméa

In vitro anti-obesity activity by pancreatic lipase inhibition - Simple HPLC approach using EVOO as natural substrate

BACKGROUND

Pancreatic lipase (PL) is a key lipolytic enzyme in humans for the digestion and absorption of dietary fats. Thereby, PL is a well-recognized target in the management of obesity and its inhibition attracts the interest of researchers globally. The screening of new natural PL inhibitors as alternative strategy to the synthesis of chemical ones represents nowadays a hot topic in research. The main challenge in this matter is the lack of a universal analytical method allowing the monitoring of PL activity and the reliable quantification of lipid digestion products.

RESULTS

The (normal phase)-high-performance liquid chromatography-evaporative light scattering detector [(NP)-HPLC-ELSD] method proposed in this work represents a direct and rapid strategy to simultaneously quantify the products obtained from in vitro PL digestion. As one of the main novelties, the triacylglycerol (TAG) fraction from extra-virgin olive oil was selected as natural substrate. The PL activity was measured by monitoring the levels of remaining TAGs and formed free fatty acids (FFAs), using Orlistat as known inhibitor. The method validation confirmed the adequacy of the analytical method for quantitative purposes, showing high recovery percentage values (between 99% and 103%) and low relative standard deviation (RSD%) values (between 2% and 7%) for triolein and oleic acid standard solutions, as well as appreciably low limit of detection (LOD) and limit of quantification (LOQ) values (respectively 58 and 177 ng mL-1 for triolein; 198 and 602 ng mL-1 for oleic acid). Finally, the developed HPLC-ELSD method was successfully applied to evaluate the inhibitory effect of a polyphenolic extract obtained from apple pomace. The results showed a comparable inhibition degree between a 4.0 mg mL-1 apple pomace solution and a 1.0 μg mL-1 Orlistat solution.

CONCLUSION

The proposed innovative method reveals highly sensitive and simple to follow the fate of PL digestion, thus opening the way to further investigations in the research of new potentially anti-obesity compounds. © 2022 Society of Chemical Industry.

Microbial Control of Sea Spray Aerosol Composition: A Tale of Two Blooms

With the oceans covering 71% of the Earth, sea spray aerosol (SSA) particles profoundly impact climate through their ability to scatter solar radiation and serve as seeds for cloud formation. The climate properties can change when sea salt particles become mixed with insoluble organic material formed in ocean regions with phytoplankton blooms. Currently, the extent to which SSA chemical composition and climate properties are altered by biological processes in the ocean is uncertain. To better understand the factors controlling SSA composition, we carried out a mesocosm study in an isolated ocean-atmosphere facility containing 3,400 gallons of natural seawater. Over the course of the study, two successive phytoplankton blooms resulted in SSA with vastly different composition and properties. During the first bloom, aliphatic-rich organics were enhanced in submicron SSA and tracked the abundance of phytoplankton as indicated by chlorophyll-a concentrations. In contrast, the second bloom showed no enhancement of organic species in submicron particles. A concurrent increase in ice nucleating SSA particles was also observed only during the first bloom. Analysis of the temporal variability in the concentration of aliphatic-rich organic species, using a kinetic model, suggests that the observed enhancement in SSA organic content is set by a delicate balance between the rate of phytoplankton primary production of labile lipids and enzymatic induced degradation. This study establishes a mechanistic framework indicating that biological processes in the ocean and SSA chemical composition are coupled not simply by ocean chlorophyll-a concentrations, but are modulated by microbial degradation processes. This work provides unique insight into the biological, chemical, and physical processes that control SSA chemical composition, that when properly accounted for may explain the observed differences in SSA composition between field studies.

Modelling the spatial and temporal variability of the SW lagoon of New Caledonia II: realistic 3D simulations compared with in situ data

Coral reef lagoons are under the growing influence of anthropogenic activities, leading to increasing loads of nutrients and various contaminants. Modelling approaches are a useful tool for studying such a complex coastal environment. In this study, we carried out the development of a three-dimensional coupled hydrodynamical-biogeochemical model of the south-west lagoon of New Caledonia. The biogeochemical model presented in Faure et al. (2006, 2010) was dynamically coupled with a hydrodynamical model (MARS3D) in order to study the short-term variability of the ecosystem. Two simulations (in winter and summer) were then performed from measured initial conditions using realistic wind and irradiance conditions and river inputs. Examinations of the biogeochemical response to these transient meteorological conditions were presented and compared with temporal field data corresponding to the considered periods. Results highlighted the ecosystem functioning, based on the balance of hydrodynamical and biogeochemical processes. Influence of urban and terrigeneous inputs were limited to the coastal zone. The model accurately reproduced the measured Chl.a and bacterial production, highlighting the improvement made on the biogeochemical model. However, the underestimation of some variables in model outputs, in particular nutrients, led us to focus on different inputs, such as sediment inputs which were not taken into account or properly estimated. Moreover, the role of boundary waters appeared crucial and suggested a calibration effort. Last, the final aim of our modelling study will help the development of a useful tool for studying the key processes of the ecosystem of the south-west lagoon of New Caledonia, as well as the examination of the biogeochemical response under different scenarios.