Resorcinol alkyl glucosides as potent tyrosinase inhibitors

Resorcinol alkyl glucosides 7–12 were developed as novel tyrosinase inhibitors based on the structure of rhododendrin. These were synthesized from 2,4-dibenzyloxybenzaldehyde using either the Wittig or the Horner-Wadsworth-Emmons reaction with Koenigs-Knorr glycosylation as key steps. The tyrosinase inhibitory activity of 7–12 increased with the length of the alkyl spacer between resorcinol and glucose. The 50% inhibitory concentration (IC₅₀) of tetradecyl derivative 12 was 0.39?μM, making it the most potent of the compounds synthesized. The IC₅₀ of 8 (3.62?μM) with a propyl spacer was ca 10?times that of 7 (35.9?μM) with an ethyl spacer. This significant activity difference suggests that an interaction between resorcinol alkyl glucoside and tyrosinase may increase remarkably if the length of the alkyl spacer exceeds C₃.     

Enzymatic synthesis of alkyl glucosides using <Emphasis Type="Italic">Leuconostoc</Emphasis> <Emphasis Type="Italic">mesenteroides</Emphasis> dextransucrase

Alkyl glucosides were synthesized by the reaction of Leuconostoc mesenteroides dextransucrase with sucrose and various alcohols. Alkyl α-d-glucosides were obtained with a yield of 30% (mol/mol) with primary alcohols, but secondary alcohols or tertiary alcohols gave yields below 5%. The optimal yield was 50% using 1-butyl α-d-glucoside with 0.9 M 1-butanol. The acceptor products of methanol or ethanol were confirmed as methyl α-d-glucopyranoside and ethyl α-d-glucopyranoside via MALDI-TOF MS and NMR analysis. Thus, methyl or ethyl α-d-glucoside constituted half the emulsification activities of Triton X-100 as commercially available surfactants. Young-Min Kim and Byung-Hoon Kim contributed equally to this work.     

Phenolics and antimicrobial activity of traditional stoned table olives 'alcaparra'

In the present work, we report the determination of phenolic compounds in ‘alcaparra’ table olives by reversed-phase HPLC/DAD, and the evaluation of their extract in vitro activity against several microorganisms that may be causal agents of human intestinal and respiratory tract infections, namely Gram positive (Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus), Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae) and fungi (Candida albicans and Cryptococcus neoformans). Three flavonoidic compounds were identified and quantified: luteolin 7-O-glucoside, apigenin 7-O-glucoside, and luteolin. At low concentrations (0.05 mg/mL) ‘alcaparra’ extract revealed significant inhibition of both Gram positive and Gram negative bacteria growth, with exception of P. aeruginosa. Nevertheless, no antifungal activity was observed at the tested concentrations.     

Preparative isolation and purification of four flavonoids from the petals of nelumbo nucifera by high‐speed counter‐current chromatography

Introduction – Flavonoids, the primary constituents of the petals of Nelumbo nucifera, are known to have antioxidant properties and antibacterial bioactivities. However, efficient methods for the preparative isolation and purification of flavonoids from this plant are not currently available. Objective – To develop an efficient method for the preparative isolation and purification of flavonoids from the petals of N. nucifera by high‐speed counter‐current chromatography (HSCCC). Methodology – Following an initial clean‐up step on a polyamide column, HSCCC was utilised to separate and purify flavonoids. Purities and identities of the isolated compounds were established by HPLC‐PAD, ESI‐MS, ¹H‐NMR and ¹³C‐NMR. Results – The separation was performed using a two‐phase solvent system composed of ethyl acetate–methanol–water–acetic acid (4 : 1 : 5 : 0.1, by volume), in which the upper phase was used as the stationary phase and the lower phase was used as the mobile phase at a flow‐rate of 1.0 mL/min in the head‐to‐tail elution mode. Ultimately, 5.0 mg syringetin‐3‐O‐β‐d‐glucoside, 6.5 mg quercetin‐3‐O‐β‐d‐glucoside, 12.8 mg isorhamnetin‐3‐O‐β‐d‐glucoside and 32.5 mg kaempferol‐3‐O‐β‐d‐glucoside were obtained from 125 mg crude sample. Conclusion – The combination of HSCCC with a polyamide column is an efficient method for the preparative separation and purification of flavonoids from the petals of N. nucifera. Copyright © 2009 John Wiley & Sons, Ltd.     

海芒果的毒性研究及其开发利用(综述)

简述海芒果毒性研究的历史、现状以及国内外研究进展,讨论海芒果毒性研究及开发利用中存在的问题,并展望其未来的研究前景。     

Chemical Constituents from the Flowers of Wild Gardenia jasminoides J.Ellis

Four new iridoids, 2′‐O‐(E)‐coumaroylshanzhiside ( 1 ), 6′‐O‐(E)‐coumaroylshanzhiside ( 2 ), 8α‐butylgardenoside B ( 3 ), 6α‐methoxygenipin ( 4 ), and one new phenylpropanoid glucoside, 5‐(3‐hydroxypropyl)‐2‐methoxyphenyl β‐d ‐glucopyranoside ( 5 ), together with sixteen known compounds, were isolated from the edible flowers of wild Gardenia jasminoides J.Ellis . Their chemical structures were characterized by extensive spectroscopic techniques, including 1D‐ and 2D‐NMR, HR‐ESI‐MS, and CD experiments. The absolute configurations of the new isolates’ sugar moiety were assigned by HPLC analysis of the acid hydrolysates. Furthermore, the antioxidant activities of those isolates were preliminarily evaluated by DPPH scavenging experiment. And comparison of ¹H‐NMR spectra for the EtOH extract of G. jasminoides J.Ellis , gardenoside B and geniposide revealed that the flowers of this plant have a considerable content of gardenoside B instead of geniposide in the fruits, indicating different activities and applications in people's daily life.     

Synthesis of multiply 13C-labeled furofuran lignans using 13C-labeled cinnamyl alcohols as building blocks

Plant lignans are currently being widely studied for their potential benefits for human health as their consumption has been correlated with lower risks for developing chronic diseases, such as breast cancer and coronary heart disease. However, studies of some classes of lignans, in particular the furofurans, are hampered by the lack of suitable standards to allow accurate analysis. Herein, we report the syntheses of two racemic (13)C-labeled furofuran lignans [7,8,9-(13)C(3)]medioresinol and [7,8,9-(13)C(3)]sesamin as internal standards for LC-MS analysis. The labeled furofuran lignans were constructed from triply labeled cinnamyl alcohols, using a radical cyclization method.     

木槿的化学成分研究

为了解木槿(Hibiscus syriacus)茎的化学成分,采用MCI-gel中压柱层析、硅胶柱层析、Sephadex LH-20凝胶柱层析和高效液相色谱等色谱方法,从木槿茎85％乙醇提取物中分离得到13个化合物.根据理化性质和波谱数据,其结构分别鉴定为methyl 4-[2-hydroxy-2-(4-hydroxy...     

Iridoid glucosides from the leaves of Vitex negundo var. cannabifolia

Five new iridoid glucosides, cannabifolisides A–E (1 – 5), together with nine analogues (6 – 14), were isolated from the leaves of Vitex negundo var. cannabifolia. Their structures were elucidated by spectroscopic data (NMR, UV, IR, and MS) analyses and comparison of their spectroscopic and physical data with the literature values. The protective effect of isolated compounds on human gastric epithelial cells were evaluated by measuring the enhanced cell viability of GES-1 cell insulted by TCA. Among these, compounds 4, 6, 8, 10, 12, and 14 remarkably increased the cell viability in a concentration-depend manner.