Distribution of arsenic species in the freshwater crustacean Procambarus clarkii

The concentrations of total arsenic and arsenic species in the complete organism of the crayfish Procambarus clarkii and its various parts (hepatopancreas, tail, and remaining parts) were analyzed in order to discover the distribution of arsenic and its species. With this information it will be possible to establish where the chemical forms of this metalloid tend to accumulate and what risks may derive from the contents and species present in the edible parts of this crustacean. The total arsenic content in the complete organism and in the various parts analyzed ranged from 2.5 to 12 µg g^?1 dry mass (DM), with inorganic arsenic representing 18 to 34% of total arsenic. The arsenical composition varied according to the part of the crayfish considered. The hepatopancreas had the highest levels of total arsenic (9.2–12 µg g^?1 DM) and inorganic arsenic (2.7–3.2 µg g^?1 DM). The tail (edible part) had the lowest levels of both total arsenic (2.5–2.6 µg g^?1 DM) and inorganic arsenic (0.46–0.64 µg g^?1 DM). The predominant organoarsenical species were the dimethylarsinoylribosides: glycerol riboside in the hepatopancreas, sulfate riboside in the tail, and sulfonate and phosphate ribosides in the remaining parts. Copyright © 2002 John Wiley & Sons, Ltd.     

Metabolic fingerprinting using direct flow injection electrospray ionization tandem mass spectrometry for the characterization of proanthocyanidins from the barks of Hancornia speciosa

Direct flow injection electrospray ionization ion trap tandem mass spectrometry (ESI-IT-MS/MS) was used to investigate the polyphenolic compounds present in an infusion from the barks of Hancornia speciosa Gom. (Apocynaceae), a native Brazilian plant popularly known as 'mangabeira', used as a source of nutrition and against gastric disorders. After a simple sample filtration pretreatment the characteristic fingerprint of the infusion was performed in negative ion ESI mode in a few minutes. At low capillary-voltage activation, the deprotonated molecules ([M--H]-) were observed and using collision-induced dissociation the product ion spectra showed the presence of a homologous series of B-type proanthocyanidins, as well as another series containing their respective C-glycosylated derivatives, with a degree of polymerization from 1 up to 6 units of interlinked catechins. Therefore, direct flow injection allowed us to identify the key compounds without preparative isolation of the components.     

Towards long-term colloidal stability of silica-based nanocarriers for hydrophobic molecules: beyond the Stöber method

The highly uniform micro- and mesoporous SiO(2) nanoparticles (40-70 nm) are hierarchically functionalized with antagonistic groups: hydrophobic (phenyl) on the internal pores and hydrophilic (methyl-phosphonate) on the external surface. Considering the large hydrophobic internal coating and the long-term colloidal stability, these systems are suitable nanocarriers by using the host-guest approach.     

Chemical analysis and quality control of Ginkgo biloba leaves,extracts, and phytopharmaceuticals

The chemical analysis and quality control of Ginkgo leaves, extracts, phytopharmaceuticals and some herbal supplements is comprehensively reviewed. The review is an update of a similar, earlier review in this journal [T.A. van Beek, J. Chromatogr. A 967 (2002) 21–55]. Since 2001 over 3000 papers on Ginkgo biloba have appeared, and about 400 of them pertain to chemical analysis in a broad sense and are cited herein. The more important ones are discussed and, where relevant, compared with the best methods published prior to 2002. In the same period over 2500 patents were filed on Ginkgo and the very few related to analysis are mentioned as well. Important constituents include terpene trilactones, i.e. ginkgolide A, B, C, J and bilobalide, flavonol glycosides, biflavones, proanthocyanidins, alkylphenols, simple phenolic acids, 6-hydroxykynurenic acid, 4-O-methylpyridoxine and polyprenols. In the most common so-called “standardised” Ginkgo extracts and phytopharmaceuticals several of these classes are no longer present. About 130 new papers deal with the analysis of the terpene trilactones. They are mostly extracted with methanol or water or mixtures thereof. Supercritical fluid extraction and pressurised water extraction are also possible. Sample clean-up is mostly by liquid–liquid extraction with ethyl acetate although no sample clean-up at all in combination with LC/MS/MS is gaining in importance. Separation and detection can be routinely carried out by RP-HPLC with ELSD, RI or MS, or by GC/FID or GC/MS after silylation. Hydrolysis followed by LC/MS allows the simultaneous analysis of terpene trilactones and flavonol aglycones. No quantitative procedure for all major flavonol glycosides has yet been published because they are not commercially available. The quantitation of a few available glycosides has been carried out but does not serve a real purpose. After acidic hydrolysis to the aglycones quercetin, kaempferol and isorhamnetin and separation by HPLC, quantitation is straightforward and yields by recalculation an estimation of the original total flavonol glycoside content. A profile of the genuine flavonol glycosides can detect poor storage or adulteration. Although the toxicity of Ginkgo alkylphenols upon oral administration has never been undoubtedly proven, most suppliers limit their content in extracts to 5 ppm and dozens of papers on their analysis were published. One procedure in which a methanolic extract is directly injected on a C8 HPLC column appears superior in terms of sensitivity (<5 ppm), separation, simplicity and validation and will be incorporated in the European Pharmacopoeia. Alternatively GC/MS and ELISA methods can be used. A sharp contrast to the plethora of papers on terpene trilactones, flavonol glycosides, and ginkgolic acids forms the low number of papers on biflavones, proanthocyanidins, simple phenolics, simple acids, and other constituents that make up the remaining 70% of Ginkgo standardised extracts. More research in this direction is clearly needed. For the analysis of Ginkgo proanthocyanidins (7%) for instance, no reliable assays are yet existing. Finally the growing literature on pharmacokinetic and fingerprinting studies of Ginkgo is briefly summarised.     

Application of liquid chromatography/electrospray ionization tandem mass spectrometry to the analysis of polyphenolic compounds from an infusion of Byrsonima crassa Niedenzu

A fast and reliable method, based on high-performance liquid chromatography coupled to electrospray ionization ion trap tandem mass spectrometry (HPLC/ESI-ITMS), was developed to investigate the infusion prepared from the leaves of Byrsonima crassa Niedenzu (Malpighiaceae), a native plant used in Brazil against gastric disorders. The use of on-line reverse-phase HPLC/ESI-ITMS allowed separation of three major classes of compounds and identification of over 20 very polar compounds characterized as galloylquinic acids, proanthocyanidins, and flavonoid glycosides, as well as the dimeric flavonoid amentoflavone and minor amounts of galloyl hexose and galloyl saccharose. This approach provided data that will allow establishment of a method for a future standardization of the infusion.     

Optimization of the solubilization, extraction and determination of inorganic arsenic [As(III) + (As(V)] in seafood products by acid digestion, solvent extraction and hydride generation atomic absorption spectrometry

A method for the selective quantitative determination of inorganic arsenic [As(III) + As(V)] in seafood was developed. In order to do so, various procedures for the solubilization and extraction of inorganic arsenic quoted in the literature were tested. None provided satisfactory recoveries for As(III) and As(V) in real samples. Consequently, a methodology was developed which included solubilization with HCl and subsequent extraction with chloroform. The arsenic was solubilized in 9 mol l-1 hydrochloric acid. After reduction by hydrobromic acid and hydrazine sulfate, the inorganic arsenic was extracted into chloroform, back-extracted into 1 mol l-1 HCl, dry-ashed, and quantified by hydride generation-atomic absorption spectrometry (HG-AAS). The analytical features of the method are as follows: detection limit, 3.07 ng g-1 As (fresh mass); precision (RSD), 4.0%; recovery, As(III) 99%, As(V) 96%. In the optimized conditions, other arsenic species--dimethylarsinic acid (DMA), arsenobetaine (AB), arsenocholine (AC) and tetramethylarsonium-ion (TMA+)--were not co-extracted. However, different percentages of minor species were extracted with chloroform: monomethylarsonic acid (MMA) 100%, and trimethylarsine oxide (TMAO) 3-10%. Real samples and reference materials of seafood (DORM-1, DORM-2, TORT-2, CRM-278 and SRM-1566a) were analyzed. The analysis of DORM-1 provided an inorganic arsenic value of 124 +/- 4 ng g-1 As, dry mass (dm), which is very close to the value obtained by other authors using high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and ionic chromatography-hydride generation-atomic absorption spectrometry (IC-HG-AAS).     

Role of the Symmetry of Multipoint Hydrogen Bonding on Chelate Cooperativity in Supramolecular Macrocyclization Processes

Herein, we analyze the intrinsic chelate effect that multipoint H‐bonding patterns exert on the overall energy of dinucleoside cyclic systems. Our results indicate that the chelate effect is regulated by the symmetry of the H‐bonding pattern, and that the effective molarity is reduced by about three orders of magnitude when going from the unsymmetric ADD–DAA or DDA–AAD patterns to the symmetric DAD–ADA pattern.     

A validated LC–MS/MS method for quantitative determination of L-dopa in Fagioli di Sarconi beans (Phaseolus vulgaris L.)

An analytical method based on ultrasound assisted extraction (UAE) and liquid chromatography coupled to electrospray tandem mass spectrometry (LC–ESI/MS/MS) was validated and applied for determining L-dopa in four ecotypes of Fagioli di Sarconi beans (Phaseolus vulgaris L.), marked with the European label PGI (Protected Geographical Indication). The selectivity of the proposed method was ensured by the specific fragmentation of the analyte. Simple isocratic chromatographic conditions and mass spectrometric detection in multiple reaction monitoring (MRM) acquisition mode were used for sensitive quantification. The LC–ESI/MS/MS method was validated within a linear range of 0.001–5.000 μg/mL. Values of 0.4 and 1.1 ng/mL were obtained for the limits of detection and quantification, respectively. The repeatability, inter-day precision, and recovery values ranges were 0.6%–4.5%, 5.4%–9.9%, and 83%–93%, respectively. Fresh and dried beans, as well as pods, cultivated exclusively with organic methods avoiding any synthetic fertilizers and pesticides were analyzed showing an L-dopa content ranging from 0.020 ± 0.005 to 2.34 ± 0.05 μg/g dry weight.