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101.
A series of novel coumarin glycoside esters(1―9) was synthesized through the acylation reaction of 4-methylcoumarin-7-O-β-D-glucoside(11) with different long chain fatty acids catalyzed by lipase in organic medium. The acylation occurred regioselectively at the 6'-OH of glycosyl moiety. The enzymatic synthesis was optimized to achieve 54%―70% yield using immobilized lipase(Novozym 435, 10 mg/mL) as catalyst and acetone and pyridine(9:1, volume ratio, water content<1%) as solvent with an acyl donor/coumarin glycoside molar ratio of 10:1 at a temperature of 40―50 ℃ for 96 h. All the synthesized compounds were confirmed. 相似文献
102.
Katarína uchov Nikolaj Spodsberg Kristian B. R. Mrkeberg Krogh Peter Biely Vladimír Puchart 《Molecules (Basel, Switzerland)》2021,26(15)
This study describes the catalytic properties of a GH30_7 xylanase produced by the fungus Talaromyces leycettanus. The enzyme is an ando-β-1,4-xylanase, showing similar specific activity towards glucuronoxylan, arabinoxylan, and rhodymenan (linear β-1,3-β-1,4-xylan). The heteroxylans are hydrolyzed to a mixture of linear as well as branched β-1,4-xylooligosaccharides that are shorter than the products generated by GH10 and GH11 xylanases. In the rhodymenan hydrolyzate, the linear β-1,4-xylooligosaccharides are accompanied with a series of mixed linkage homologues. Initial hydrolysis of glucuronoxylan resembles the action of other GH30_7 and GH30_8 glucuronoxylanases, resulting in a series of aldouronic acids of a general formula MeGlcA2Xyln. Due to the significant non-specific endoxylanase activity of the enzyme, these acidic products are further attacked in the unbranched regions, finally yielding MeGlcA2Xyl2-3. The accommodation of a substituted xylosyl residue in the −2 subsite also applies in arabinoxylan depolymerization. Moreover, the xylose residue may be arabinosylated at both positions 2 and 3, without negatively affecting the main chain cleavage. The catalytic properties of the enzyme, particularly the great tolerance of the side-chain substituents, make the enzyme attractive for biotechnological applications. The enzyme is also another example of extraordinarily great catalytic diversity among eukaryotic GH30_7 xylanases. 相似文献
103.
Masaru Kojima 《Tetrahedron letters》2009,50(45):6143-3663
The total synthesis of clemochinenoside A and the first total syntheses of clemochinenoside B and berchemolide were achieved simultaneously via macrocyclization of 4-O-(4-O-F13benzyl-β-d-glucopyranosyl)syringic acid with 4-O-(4-O-F17benzyl-β-d-glucopyranosyl)vanillic acid by a fluorous mixture synthetic method. The spectroscopic data of the synthetic products were identical with those of the natural products, although the optical rotation of clemochinenoside A differed from the published values in sign and magnitude. 相似文献
104.
Three new cyanogenic glycosides named hydracyanosides A (1), B (2), and C (3) were isolated from the leaves and/or stems of Hydrangea macrophylla in China. The absolute stereostructures of hydracyanosides were characterized on the basis of chemical and physiochemical evidence including single crystal X-ray crystallographic analysis. To the best of our knowledge, this is the first scientific report of cyanogenic glycosides from Hydrangea plants. 相似文献
105.
Nine glycosides ( 1–9 ) were characterized from the n‐butanol‐soluble fraction of the ethanolic extract of the leaves of Sageretia thea by the general approach. Among these, Compounds 6 and 7 were identified as a mixture. Application of HPLC‐SPE‐NMR in two selected fractions led to the separation of this mixture and the characterization of three additional minors ( 10–12 ). Among these, 7‐O‐methylmyricetin 3‐O‐α‐l ‐arabinofuranoside ( 8 ) is a new natural product and eight compounds, i.e. glucofragulin A ( 1 ), quercetin‐3‐O‐α‐l ‐arabinopyranoside ( 5 ), 3‐O‐β‐d ‐galactopyranoside ( 6 ), 3‐O‐β‐d ‐glucopyranoside ( 7 ), and 3‐O‐α‐l ‐arabinofuranoside ( 11 ), myricetin‐3‐O‐α‐l ‐arabinofuranoside ( 9 ) and 3‐O‐β‐d‐glucopyranoside ( 10 ), and quercetrin ( 12 ), are found for the first time from the title plant. 相似文献
106.
Yuxin Wang Guangji Wang Pengfei Tu Yan Liang Hao Yang Chaonan Zheng Nan Cui 《Talanta》2009,80(2):572-1747
Metabolite identification for the compounds that undergo multiple and sequential metabolism is still a great challenge. Echinacoside (ECH), a typical phenylethanoid glycoside, contains multiple unstable chemical bonds and high reactive functional groups which are susceptible to multiple pathways of degradation and metabolism, leading great difficulties for its metabolite identification. This study proposed a novel approach for rapidly identifying the complicated and unpredictable metabolites of ECH, based on the powerful liquid chromatography hybrid ion trap and time of flight mass spectrometry (LC/MS-IT-TOF) analysis. Four degradation products were rapidly identified via the “fragmentation-degradation” comparisons. Five phase I and phase II metabolites of the degradation products were rapidly characterized via the crossover mass differences comparisons of their quasi-molecular ions with the potential precursors. Four direct phase I and phase II metabolites of the parent compound were identified by the mass differences analysis of the molecular ions between metabolites and the parent compound. Multiple stages of fragmentation patterns were used to confirm the metabolites characterizations. This study provides a novel approach to characterizing the complicated metabolites, and would be widely applicable for the metabolite identification of natural products. 相似文献
107.
UPLC-MS法同时测定牛奶中磺胺类、喹诺酮类、甾体激素类及四环素类兽药残留 总被引:2,自引:0,他引:2
建立并优化了同时测定牛奶中10种磺胺类、6种喹诺酮类、8种甾体激素类以及1种四环素类药物共25种兽药残留的超高效液相色谱-串联质谱检测方法。样品中目标药物经5%乙酸乙腈提取,HLB固相萃取小柱净化后,通过UPLC-MS测定,外标法定量。25种兽药在不同加标浓度下的回收率为61.6%~119.2%,组内相对标准偏差(RSD)为2.5%~13.4%,组间RSD为5.8%~14.2%,方法检出限为0.5~2.0μg/kg。 相似文献
108.
109.
利用红外光谱、核磁共振氢谱、紫外光谱以及质谱等表征手段对一种新型蛋白同化激素(AAS)口服药物的主成分进行了研究和鉴定,推定主成分为甲基-1-睾酮(methyl-1-testosterone, M1T, 17β-hydroxy-17α-methyl-5α-androst-1-en-3-one)。在此基础上,建立了M1T的气相色谱-质谱联用检测方法。方法的检出限(信噪比(S/N)为3)为2 ng/mL,定量限(S/N=10)为10 ng/mL;7次平行测定前处理后的加内标尿样的相对标准偏差为9.8%。用该方法测定了该药物在尿样中的排泄曲线。该方法的建立为AAS新药的发现、检测和监控做了很有意义的基础研究工作。 相似文献
110.