A new approach towards acid catalysts with high reactivity based on graphene nanosheets

Wei, Zuojun,Yang, Yao,Hou, Yaxin,Liu, Yingxin,He, Xiaodong,Deng, Shuguang

, p. 2354 - 2363 (2014)

Solid acid catalysts of graphene oxide and sulfonated graphene oxide nanosheets have been prepared by using the modified Hummers and sulfonation methods. Physical characterization indicated that a number of functional groups such as -COOH, -OH, -O-, and -SO3H were introduced onto the surfaces of the as-synthesized nanosheets. The catalytic performance of the synthesized catalysts was evaluated in the hydrolysis of the glycosidic bond and Fischer esterification. The experimental results indicated that the catalytic activity of the sulfonated graphene oxide was superior to that of other solid acid catalysts with the same or higher acid strength and has also exceeded that of H2SO4 with 9.1 times of acid strength than that of the sulfonated graphene oxide. The high reactivity can be ascribed to the formation of hydrophobic cavities through the combination of graphene sheet and the oxygen-containing groups on its surface, which may facilitate the catalyst to anchor with reactants and promote the attack of protons.

Formation of 6,7,4'-trihydroxyisoflavone (factor 2) from soybean seed isoflavones by bacteria isolated from tempe

Klus,Borger-Papendorf,Barz

, p. 979 - 981 (1993)

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Harborne et al.

, p. 881 (1963)

Enzymatic studies of isoflavonoids as selective and potent inhibitors of human leukocyte 5-lipo-oxygenase

Mascayano, Carolina,Espinosa, Victoria,Sepúlveda-Boza, Silvia,Hoobler, Eric K.,Perry, Steve,Diaz, Giovanni,Holman, Theodore R.

, p. 894 - 901 (2015/06/23)

Continuing our search to find more potent and selective 5-LOX inhibitors, we present now the enzymatic evaluation of seventeen isoflavones (IR) and nine isoflavans (HIR), and their in vitro and in cellulo potency against human leukocyte 5-LOX. Of the 26 compounds tested, 10 isoflavones and 9 isoflavans possessed micromolar potency, but only three were selective against 5-LOX (IR-2, HIR-303, and HIR-309), with IC50 values at least 10 times lower than those of 12-LOX, 15-LOX-1, and 15-LOX-2. Of these three, IR-2 (6,7-dihydroxy-4-methoxy-isoflavone, known as texasin) was the most selective 5-LOX inhibitor, with over 80-fold potency difference compared with other isozymes; Steered Molecular Dynamics (SMD) studies supported these findings. The presence of the catechol group on ring A (6,7-dihydroxy versus 7,8-dihydroxy) correlated with their biological activity, but the reduction of ring C, converting the isoflavones to isoflavans, and the substituent positions on ring B did not affect their potency against 5-LOX. Two of the most potent/selective inhibitors (HIR-303 and HIR-309) were reductive inhibitors and were potent against 5-LOX in human whole blood, indicating that isoflavans can be potent and selective inhibitors against human leukocyte 5-LOX in vitro and in cellulo. Of the 26 compounds tested, 10 isoflavones and 9 isoflavans possessed micromolar potency, but only three were selective against 5-LOX (IR-2, HIR-303, and HIR-309), with IC50 values at least 10 times lower than those of 12-LOX, 15-LOX-1, and 15-LOX-2. Docking and steered molecular dynamics were performed to determinate the structure-activity relationship.