Acylated secoiridoid glucosides isolated from the fruit extract of Symplocos lucida inhibit β-glucuronidase

Two new acylated secoiridoid glucosides, designated symplolucidins A and B, were isolated from the fruit extract of Symplocos lucida (Thunb.) Siebold & Zucc. Their structures, including their absolute configurations, were elucidated by extensive spectroscopic analyses and chemical reactions. They were found to exhibit β-glucuronidase inhibitory effect.     

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.     

Frequency of cyanogenesis in tropical rainforests of far north Queensland, Australia

BACKGROUND AND AIMS: Plant cyanogenesis is the release of toxic cyanide from endogenous cyanide-containing compounds, typically cyanogenic glycosides. Despite a large body of phytochemical, taxonomic and ecological work on cyanogenic species, little is known of their frequency in natural plant communities. This study aimed to investigate the frequency of cyanogenesis in Australian tropical rainforests. Secondary aims were to quantify the cyanogenic glycoside content of tissues, to investigate intra-plant and intra-population variation in cyanogenic glycoside concentration and to appraise the potential chemotaxonomic significance of any findings in relation to the distribution of cyanogenesis in related taxa. METHODS: All species in six 200 m(2) plots at each of five sites across lowland, upland and highland tropical rainforest were screened for cyanogenesis using Feigl-Anger indicator papers. The concentrations of cyanogenic glycosides were accurately determined for all cyanogenic individuals. KEY RESULTS: Over 400 species from 87 plant families were screened. Overall, 18 species (4.5 %) were cyanogenic, accounting for 7.3 % of total stem basal area. Cyanogenesis has not previously been reported for 17 of the 18 species, 13 of which are endemic to Australia. Several species belong to plant families or orders in which cyanogenesis has been little reported, if at all (e.g. Elaeocarpaceae, Myrsinaceae, Araliaceae and Lamiaceae). A number of species contained concentrations of cyanogenic glycosides among the highest ever reported for mature leaves-up to 5.2 mg CN g(-1) d. wt, for example, in leaves of Elaeocarpus sericopetalus. There was significant variation in cyanogenic glycoside concentration within individuals; young leaves and reproductive tissues typically had higher cyanogen content. In addition, there was substantial variation in cyanogenic glycoside content within populations of single species. CONCLUSIONS: This study expands the limited knowledge of the frequency of cyanogenesis in natural plant communities, includes novel reports of cyanogenesis among a range of taxa and characterizes patterns in intra-plant and intra-population variation of cyanogensis.     

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。     

Maltol glucosides from the tuber of Smilax bockii

Two maltol glucosides, bockiosides A and B, along with 10 known compounds, were isolated from the tuber of Smilax bockii (Liliaceae), and their structures were elucidated by spectral experiments, chemical analysis and comparison with literature data.     

Transglucosylation of tertiary alcohols using cassava beta-glucosidase

We have compared the ability of beta-glucosidases from cassava, Thai rosewood, and almond to synthesize alkyl glucosides by transglucosylating alkyl alcohols of chain length C(1)-C(8). Cassava linamarase shows greater ability to transfer glucose from p-nitrophenyl-beta-glucoside to secondary alcohol acceptors than other beta-glucosidases, and is unique in being able to synthesize C(4), C(5), and C(6) tertiary alkyl beta-glucosides with high yields of 94%, 82%, and 56%, respectively. Yields of alkyl glucosides could be optimized by selecting appropriate enzyme concentrations and incubation times. Cassava linamarase required pNP-glycosides as donors and could not use mono- or di-saccharides as sugar donors in alkyl glucoside synthesis.