Fucoxanthin (Fuco) is a characteristic carotenoid of brown seaweeds. In the present study, Fuco and its stereoisomers 9'Z-Fuco, 13Z- and 13'Z-Fuco were extracted from Laminaria japonica Aresch. They were isolated and purified by silica gel column chromatography, Sephadex LH-20, and reversed-phase HPLC. The radical-scavenging activities of the three stereoisomers were evaluated toward 1,1-diphen...

Hydrothermally synthesized high silica borosilicates with the MFI structure was subjected to several characterization techniques. The effect of boron on the structure and acidity of HZSM-5 catalyst were studied by XRD, SEM, N2 adsorption, solid state NMR, NH3-TPD. It was confirmed that boron had entered the framework in the boron samples. The results also revealed that strong acidity was weaken...

Bulk boron materials, such as hexagonal nitride (h-BN), are highly selective catalysts for the oxidative dehydrogenation of propane (ODHP). Previous attempts to improve productivity these systems involved immobilization on silica and resulted in less catalysts. Here, we report that acid-treated, activated carbon-supported prepared via incipient wetness impregnation with boric acid (B/OAC) exhib...

We have studied the direct synthesis of hydrogen peroxide using a catalytic system consisting palladium supported on silica bifunctionalized with sulfonic acid groups and bromide in absence halide promoters solution. Catalysts several substituents were employed catalyst synthesis. The prepared samples characterized by TXRF, XPS, decomposition. characterization indicated presence only (II) speci...

Sulfonic acid-based precursors (SAP) play an important role in tailoring mesoporous silica’s and convert them to a solid acid catalyst with a Bronsted-type nature. These kinds of solid acids contribute to sustainable and green chemistry by their heterogeneous, recyclable, and high efficiency features. Therefore, knowing the properties and reactivity of SAPs can guide us to manufacture a sulfona...

3,4-dihydropyrimidin-2(1H)-thiones were synthesized in the presence of Ag nanoparticle/melamine sulfonic acid (MSA) supported on silica gel. The reaction was carried out at 110 oC for 20 min under solvent free conditions. In all cases, the three component reaction proceeded smoothly to give the corresponding 3,4-dihydropyrimidin-2(1H)-thiones in moderate to good yield. We have found the best co...

Based on first-principles density-functional calculations, we present the structure and diffusion of boron in amorphous silica, as well as in crystalline silica for comparison purpose. We find that incorporation of a boron atom into the amorphous silica matrix results in various minimum-energy configurations with and without oxygen deficient centers, and also the B-related defects can undergo i...

sulfonic acid functionalized sba-15 (sba-pr-so3h) with pore size 6 nm as an efficient heterogeneous nanoporous solid acid catalyst exhibited good catalytic activity in the biginelli-like reaction in the synthesis of spiroheterobicyclic rings with good yield and good recyclability. spiro-pyrimidinethiones/spiro-pyrimidinones-barbituric acid derivatives were synthesized in a simple and efficient ...

Boron (B) is a non-metal micronutrient which is essential for plants growth and development. Formation of boron complex with cell wall matrix and phenolic compounds is a definite influence of boron in physiological process. It has been suggested that B-toxicity and deficiency may induce excess production of reactive oxygen species thereby promote defense responses by antioxidant enzymes or non-...

this study was carried out in order to determine the effects of boron and cold stress on pollen germination of almond hybrids in vitro culture, two different media including the absence and presence of boron (0 mg/l, and 100 mg/l) in 10% sucrose and 1% agar medium at 24°c in dark conditions. the results showed that different treatments had a significant effect on the germination percentage. the...