Search Results (4)

Monosaccharide composition analysis is essential to the structural characterization and research into the biological activity of polysaccharides. In this study, a systematic comparison was performed among commonly used monosaccharide composition analysis methods, including colorimetric and chromatographic methods. These were tested on 16 aldoses, ketoses, alditols, amino sugars, and uronic acids. Furthermore, the effect of hydrolysis methods was also investigated. The results showed that the phenol sulfuric acid method is greatly affected by the type of monosaccharide that is used as the reference substance. The determination of uronic acid using sulfuric acid carbazole is less affected by neutral sugars than that method using m-hydroxybiphenyl. The high-performance thin-layer chromatography (HPTLC) method can simultaneously analyze multiple samples and accurately determine the type of uronic acid. High-performance liquid chromatography (HPLC) can provide a good qualitative and quantitative analysis of aldose, amino sugars, and uronic acids, while gas chromatography–mass spectrometry (GC-MS) can detect aldose, ketose, and alditols. Fructose was detected in a large amount in inulin and Codonopsis pilosula after one-step hydrolysis, while it was totally destroyed in two-step hydrolysis. The release of galacturonic acid significantly increased after two-step hydrolysis in pectin and Lycium barbarum, which indicated that one-step hydrolysis is not enough for acidic polysaccharides. The results of this study are beneficial for selecting appropriate hydrolysis and analysis methods in order to accurately analyze the monosaccharide compositions of natural polysaccharides. Full article

Studies of marine aggregation have focused on determining formation rates of larger particles from small particles. However, it has been shown that particles can form from the dissolved phase, which includes colloidal material. The purpose of this study was to investigate the effect of aggregation on the chemical composition of both the dissolved and particulate phases in two salinity regimes: (1) the coast of Avery Point, Connecticut, USA (AP; salinity of 30.1 psu); (2) the estuary of Thames River, Connecticut, USA (TR; salinity of 5.0 psu). The samples were incubated on a roller table for two days in the dark at a speed of 8 rpm. The mixed collision mechanism of shear and differential sedimentation provided by the roller table enhanced the gross aggregation of particulate organic carbon (POC; 0.75 µM d⁻¹ and 1.04 µM d⁻¹ in AP and TR, respectively). Subsequent microbial degradation led to a negative net aggregation of POC (−5.20 µM d⁻¹ and −1.19 µM d⁻¹ in AP and TR, respectively). Although bacterial abundance remained in a narrow range in this study, the aggregation of organic matter (OM) enhanced planktonic community respiration (CR; CR increased 5.1 mg-C m⁻³ d⁻¹ and 205.4 mg-C m⁻³ d⁻¹ in AP and TR, respectively). The collision also led to a gross aggregation of uncharacterized particulate organic matter (POM) transferred from uncharacterized dissolved organic matter (DOM; 0.62 µM-C d⁻¹ and 0.56 µM-C d⁻¹ in AP and TR, respectively). The aggregated, uncharacterized POM could be biologically refractory. The C- and N-yields and enrichment factor (EF) analysis indicated that the organic substrate dynamics in this study were complicated. Full article

A cataract is a condition that causes 17 million people to experience blindness and is the most significant cause of vision loss, around 47.9%. The formation of cataracts is linked to both the production of reactive oxygen species (ROS) and the reduction of endogenous antioxidants. ROS are highly reactive molecules produced by oxygen. Examples of ROS include peroxides, super-oxides, and hydroxyl radicals. ROS are produced in cellular responses to xenobiotics and bacterial invasion and during mitochondrial oxidative metabolism. Excessive ROS can trigger oxidative stress that initiates the progression of eye lens opacities. ROS and other free radicals are highly reactive molecules because their outer orbitals have one or more unpaired electrons and can be neutralized by electron-donating compounds, such as antioxidants. Examples of natural antioxidant compounds are vitamin C, vitamin E, and beta-carotene. Numerous studies have demonstrated that plants contain numerous antioxidant compounds that can be used as cataract preventatives or inhibitors. Natural antioxidant extracts for cataract therapy may be investigated further in light of these findings, which show that consuming a sufficient amount of antioxidant-rich plants is an excellent approach to cataract prevention. Several other natural compounds also prevent cataracts by inhibiting aldose reductase and preventing apoptosis of the eye lens. Full article

Organic aggregates, which formed from small particles and dissolved material, were chemically characterized in the Long Island Sound coastal waters. In this study, six aggregation experiments were conducted on low-salinity samples (the Thames River, CT, USA; salinity of 6.3–6.8) and high-salinity samples (the coast of Avery Point, CT, USA; salinity of 21.4–26.7). Water samples were incubated on a roller table for two days under dark conditions to generate laboratory-made aggregates. Particulate organic carbon (POC) concentrations increased 5–39% after two days of rolling. A higher POC increase occurred in low-salinity samples. The concentrations of neutral aldoses and amino acids, as well as their C- and N-yields, decreased during the experiments (except for particulate hydrolysable amino acid in low-salinity samples), while bacterial abundance increased 50–476%, indicating microbial degradation of biologically labile organic matter. Particulate hydrolysable amino acid was preferentially preserved in P-limited systems. An enrichment factor analysis showed the preferential microbial degradation of particulate hydrolysable neutral aldose and glucose appeared as the most labile aldose. The increase in bulk POC and the decrease in the fraction of labile organic carbon (neutral aldose and amino acid) in the particulate phase resulted in an accumulation of uncharacterized (presumably more refractory) particulate organic matter. Full article