Recent scholarship has recognized some thematic connections related to onto-cosmological issues between two late Platonic dialogues, such as Philebus and Timaeus, and has tried to explain them in ...different ways. The aim of this paper is to contribute to such a debate by analysing an ancient exegesis of Timaeus 35a1-b4, that of Plutarch of Chaeronea, which made use of the ontological sections of the Philebus (16c-17a and 23c-27c) in his treatise on the cosmogony of the Timaeus. More specifically, this analysis will show that the notions of ‘limit’ and ‘unlimitedness’ played a decisive role in the shaping of the “essence” of the world-soul according to Plutarch.
Isoflavones are plant-derived natural products commonly found in legumes that show a large spectrum of biomedical activities. A common antidiabetic remedy in traditional Chinese medicine,
L. contains ...the isoflavone formononetin (FMNT). Literature reports show that FMNT can increase insulin sensitivity and potentially target the peroxisome proliferator-activated receptor gamma, PPARγ, as a partial agonist. PPARγ is highly relevant for diabetes control and plays a major role in Type 2 diabetes mellitus development. In this study, we evaluate the biological role of FMNT, and three related isoflavones, genistein, daidzein and biochanin A, using several computational and experimental procedures. Our results reveal the FMNT X-ray crystal structure has strong intermolecular hydrogen bonding and stacking interactions which are useful for antioxidant action. Cyclovoltammetry rotating ring disk electrode (RRDE) measurements show that all four isoflavones behave in a similar manner when scavenging the superoxide radical. DFT calculations conclude that antioxidant activity is based on the familiar superoxide σ-scavenging mode involving hydrogen capture of ring-A H7(hydroxyl) as well as the π-π (polyphenol-superoxide) scavenging activity. These results suggest the possibility of their mimicking superoxide dismutase (SOD) action and help explain the ability of natural polyphenols to assist in lowering superoxide concentrations. The SOD metalloenzymes all dismutate O
to H
O
plus O
through metal ion redox chemistry whereas these polyphenolic compounds do so through suitable hydrogen bonding and stacking intermolecular interactions. Additionally, docking calculations suggest FMNT can be a partial agonist of the PPARγ domain. Overall, our work confirms the efficacy in combining multidisciplinary approaches to provide insight into the mechanism of action of small molecule polyphenol antioxidants. Our findings promote the further exploration of other natural products, including those known to be effective in traditional Chinese medicine for potential drug design in diabetes research.
The homopoly-
l-guluronic blocks presented in the IR spectra two characteristics bands at 812 and 781
cm
−1.
Sodium alginates obtained by alkaline extraction of
Lessonia flavicans,
Desmarestia ...ligulata and
Desmarestia distans (Phaeophyta) from southern Chile were partially hydrolyzed with HCl. Each alginate gave three fractions that were characterized using FT-IR spectroscopy. The fractions soluble in 0.3
M HCl presented in the fingerprint region four vibrations at around 960, 911, 890 and 815
cm
−1 that were assigned to heteropolymeric blocks. The fractions soluble at pH 2.85 showed bands at around 948, 888 and 820
cm
−1 attributed to homopolymannuronic acid blocks, the first band is resolved in the second-derivative spectra into two bands at 951 and 936
cm
−1. The fractions insoluble at pH 2.85 presented four bands at around 947, 903, 812 and 781
cm
−1, which were assigned to homopolyguluronic acid blocks. For some samples, the second derivative FT-IR spectra showed new bands indicating the presence of other structures, in low proportions. Structures deduced by FT-IR spectroscopy were corroborated by solution
1H and
13C NMR spectroscopy. Two-dimensional spectra were collected to confirm the fine structure of the hetero- and homopolymeric fractions. A geometrically optimized model for the disaccharide α-
l-gulopyranuronosyl-(1→4)-α-
l-gulopyranuronic acid was calculated using density functional theory; good agreement was obtained between its corresponding calculated vibrations and the experimental bands assigned to homopolyguluronic acid blocks.
Malaria is a huge global health burden with resistance to currently available medicines resulting in the search for newer antimalarial compounds from traditional medicinal plants in malaria-endemic ...regions. Previous studies on two chalcones, homobutein and 5-prenylbutein, present in
, have shown moderate antiplasmodial activity. Here, we describe results from experimental and computational investigations of four structurally related chalcones, butein, 2',4'-dihydroxy-3,4-dimethoxychalcone (DHDM), homobutein and 5-prenylbutein to elucidate possible molecular mechanisms by which these compounds clear malaria parasites. The crystal structures of butein and DHDM show that butein engages in more hydrogen bonding and consequently, more intermolecular interactions than DHDM. Rotating ring-disk electrode (RRDE) voltammetry results show that butein has a higher antioxidant activity towards the superoxide radical anion compared to DHDM. Computational docking experiments were conducted to examine the inhibitory potential of all four compounds on falcipain-2, a cysteine protease that is involved in the degradation of hemoglobin in plasmodium-infected red blood cells of the host. Overall, this work suggests butein as a better antimalarial compound due to its structural features which allow it to have greater intermolecular interactions, higher antioxidant activity and to create a covalent complex at the active site of falcipain-2.
Propolis is produced by honeybees and used to seal their hives for defensive purposes and has been used in ethnopharmacology since ancient times. It is a lipophilic material containing a large ...collection of naturally produced plant organic molecules, including flavonoids. The flavonoid galangin is consistently found in propolis, independent of the hive geographical location and its X-ray crystal and molecular structure is reported. The antioxidant scavenging of superoxide by galangin and propolis is here presented. Using a cyclic voltammetry technique developed in our lab, we show that galangin is an excellent scavenger of the superoxide radical, perhaps even better than quercetin. Our results show that galangin displays a Superoxide Dismutase (SOD) function. This is described experimentally and theoretically (DFT). Two modes of scavenging superoxide are seen for galangin: (1) superoxide radical extraction of H atom from the hydroxyl moieties located in position 3 and 5 of galangin, which are also associated with proton incorporation defining the SOD action; (2) π-π interaction among several superoxide radicals and the galangin polyphenol ring that evolve towards release of O2 and H2O2. We describe these two actions separately as their relative sequence, and/or combination, cannot be defined; all these processes are thermodynamically spontaneous, or subjected to mild barriers.
Little is known about the characteristics of ambient sound in shallow waters southwest of Hainan Island, China, a tropical habitat of the Indo-Pacific humpback dolphin. The spatiotemporal patterns of ...soundscape in this area were thus studied and described here. Acoustic data collected from February 2018 to February 2019 at ten monitoring sites, spanning ~200 km of the coastline, were analyzed. The ambient sound characteristics in the investigated area showed significant spatiotemporal variations. Sound levels centered at 0.5 and 1 kHz were higher during dusk and night than other times of the day at all monitoring sites except for one. Higher sound levels at frequencies above 8 kHz were documented during autumn and winter at all sites except for three of them. Biological and anthropogenic sound sources including soniferous fishes, snapping shrimps, dolphins, ships, pile-driving activities, and explosions were identified during spectrogram analyses of a subsample of the dataset. The shipping noise was frequently detected throughout the monitoring sites. Spatiotemporal variations of the soundscape in the investigated waters provided baseline information on the local marine environment, which will be beneficial to the protection of the vulnerable Indo-Pacific humpback dolphin population recently discovered in the investigated waters.
•Kohonen map was firstly applied to monitor cetacean habitat.•Habitat differentiation in Sousa chinensis was found.•Sousa chinensis can be divided into ecotypes of estuarine and non-estuarine.•A ...specific design of marine protected areas was proposed accordingly.
Coastal cetaceans are recognized as ecologically important species and have been the target for environmental monitoring programs and conservation strategies. Although supervised models have increasingly been used to better monitor complexity relationships between cetaceans and their habitats, the development of unsupervised learning techniques that have significant advantages in visualizing, grouping and reducing the dimensionality of data has been overlooked. Here, using the unsupervised artificial neural network of self-organizing map (SOM), we examined the intraspecific variation of habitat utilization among three geographically neighboring populations (waters southwest of Hainan Island abbreviated as WS Hainan, Sanniang Bay, and Zhanjiang waters) of the Indo-Pacific humpback dolphin (Sousa chinensis) in the northern South China Sea. The results showed that the population inhabiting in WS Hainan occupied a largest area with scattered patterns comparing to the other two in Sanniang Bay and Zhanjiang waters. The SOM analysis further showed that the examined populations in different waters have distinct habitat characteristics. S. chinensis in WS Hainan was sighted in deeper water with higher salinity, whereas the population in Sanniang Bay inhabited in estuary with lower pH and salinity. More complicated distributed patterns and environmental heterogeneity were observed in Zhanjiang waters, where the dolphins distributed contractively in a small area at the entrance of Zhanjiang Port and dispersed in another large area in Leizhou Bay. Correspondently, part of the sightings in Zhanjiang waters had similar habitat with those in WS Hainan, while others were reported in more inshore, deeper and muddied waters. Based on these findings, we hypothesized that S. chinensis can be divided into two ecotypes: estuarine and non-estuarine. Here, we confirmed that the SOM can well identify the habitat differentiation in S. chinensis, and therefore suggested it is a powerful modeling tool for cetacean monitoring program. Our findings contribute to a specific habitat conservation strategy that one integrated protected area would be better for S. chinensis in Sanniang Bay and Zhanjiang waters, while several small protected areas with connecting corridors were more suitable for population in WS Hainan.
Polyphenols are valuable natural antioxidants present in our diet that likely mitigate aging effects, neurodegenerative conditions, and other diseases. However, because of their poor absorption in ...the gut and consequent low concentration in biological fluids (µM range), reservations about polyphenol antioxidant efficiency have been raised. In this review, it is shown that after scavenging superoxide radicals, coumarin, chalcone, and flavonoid polyphenols can reform themselves, becoming ready for additional cycles of scavenging, similar to the catalytic cycle in superoxide dismutase (SOD) action. The π-π interaction between one polyphenol ring and superoxide is associated with oxidation of the latter due to transfer of its unpaired electron to a polyphenolic aromatic ring, and consequent formation of a molecule of O2 (one product of SOD action). Mechanistically, it is very difficult to establish if this π-π interaction proceeds before or after the most common mode of scavenging superoxide, e.g., abstraction of an aromatic polyphenol H(hydroxyl), which then is used to form H2O2 (the other molecule produced by SOD action). At the end of this cycle of superoxide scavenging, 4-methyl-7,8-di-hydroxy-coumarin and the flavonoid galangin reform themselves. An alternative mechanistic pathway by galangin forms the η-(H2O2)-galangin-η-O2 complex that includes additional H2O2 and O2 molecules. Another mode of action is seen with the chalcone butein, in which the polyphenol system incorporates a molecule of O2, e.g., a η-O2-butein complex is formed, ready for additional scavenging. Of the several families of polyphenols analyzed in this review, only butein was able to circumvent an initial π-π interaction, directing the superoxide towards H(hydroxyl) in position 4, e.g., acting as a typical polyphenol scavenger of superoxide. This fact did not impede an additional superoxide to later react with the aromatic ring in π-π fashion. It is concluded that by mimicking SOD enzyme action, the low concentration of polyphenols in biological fluids is not a limiting factor for effective scavenging of superoxide.
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