Stability of Se species in plant extracts rich in phenolic substances

Since there is growing awareness of the strong dependence of the antioxidative function of selenium (Se) upon its chemical form, the stability of Se species during sample preparation is an important factor in obtaining qualitative and quantitative results. Many plant samples are rich in phenolic compounds (antioxidants), but data about their effect on specific Se species in extracts of plant samples are scarce. Therefore, the aim of this study was to investigate the effect of the most common phenolic substances in plant parts, namely tannin and the flavonoid rutin, on the concentration and/or transformation of several Se species (SeMet, SeCys₂, SeMeSeCys, Se(VI) and Se(IV)) during sample preparation (24 h incubation at 37 °C) and storage (4 days at 4 °C). Moreover, the effect observed was then studied in a real sample, buckwheat, because this plant is known as a rich source of phenolics, especially tannin and rutin. Se speciation was carried out by on-line coupling of ion-exchange HPLC-ICP-MS after water and enzymatic (protease) hydrolysis. The results showed that the ratio between the two antioxidants has an important role. When the antioxidants were present together, the response for Se(IV) was observed to start to decrease only at a ratio of rutin to tannin of 1:100 (w/w), indicating the ratio between antioxidants in buckwheat seeds. After water extraction, only 40% and after enzymatic extraction 80% of Se(IV) remained, but no other Se compound was detected with the system used. Furthermore, the extracts were not stable during storage at 4 °C. Signals for other Se species were stable. The results obtained for buckwheat seeds showed a decrease in Se(IV) response during sample preparation and storage, comparable to the one obtained with the experiments performed in vitro. However, Se species in extracts of other buckwheat parts (leaves, stems and sprouts) were stable. These results indicate that reactions in the extraction process and during storage may affect Se speciation and may result in misidentifications and inaccurate values.     

Tropical plant extracts as potential antihyperglycemic agents

Preliminary investigations on 14 plant extracts (obtained by ethanolic and aqueous extraction) identified those having high antioxidant and a significant total phenolic content. Antihyperglycemic, α-amylase and α-glucosidase inhibition activities were also observed. A correlation between the antihyperglycemic activity, total phenolic content and antioxidant (DPPH scavenging) activity was established. To further substantiate these findings, the possibility of tannins binding non-specifically to enzymes and thus contributing to the antihyperglycemic activity was also investigated. Our study clearly indicated that the antihyperglycemic activity observed in the plant extracts was indeed not due to non-specific tannin absorption.     

Optimization Method for Phenolic Compounds Extraction from Medicinal Plant (Juniperus procera) and Phytochemicals Screening

Juniperus procera is a natural source of bioactive compounds with the potential of antitumor, antimicrobial, insecticidal, antifungal, and antioxidant activities. An optimization method was developed for total phenolic content (TPC), total flavonoid content (TFC), and total tannin content (TTC) in leaf and seed extract of Juniperus procera. Organic solvents (methanol (99.8%), ethanol (99%), and acetone (99.5%)), and deionized water (DI) were used for extraction. The estimation of TPC, TFC, and TTC in plant materials was carried out using UV-spectrophotometer and HPLC with the standards gallic acid, quercetin, and tannic acid. Recovery of TPC in leaf extract ranged from 2.9 to 9.7 mg GAE/g DW, TFC from 0.9 to 5.9 mg QE/g DW, and TTC ranged from 1.5 to 4.3 mg TA/g DW while the TPC value in the seed extract ranged from 0.53 to 2.6 mg GAE/g DW, TFC from 0.5 to 1.6 mg QE/g DW, and TTC ranged from 0.5 to 1.4 mg TA/g DW. This result revealed that methanol is the best solvent for recovery of the TPC value (9.7 mg) from leaf extract in comparison to other solvents. Ethanol recorded the highest result of TFC (5.9 mg) in leaf extract among the solvents whereas acetone was the best for TTC yield recovery from leaf extract (4.3 mg). In the case of the seed extract, ethanol was the best solvent for both TPC (2.6 mg), and TFC (1.6 mg) recovery in comparison to other solvents. Total tannin content in methanol resulted in significant recovery from seed extract (1.4 mg). Separation and quantification of gallic acid, quercetin, and tannic acid in plant materials were undertaken using HPLC. Gallic acid in leaf and seed of J. procera ranged from 6.6 to 9.2, 6.5 to 7.2 µg/g DW, quercetin from 6.3 to 18.2, 0.9 to 4.2 µg/g DW, and tannic acid from 16.2 to 29.3, 6.6 to 9.3 µg/g DW, respectively. Solvents have shown a significant effect in the extraction of phenolic compounds. Moreover, phytochemicals in plant materials were identified using GC-MS and resulted in very important bioactive compounds, which include anti-inflammatory, antibacterial, and antitumor agents such as ferruginol, phenanthrene, and n-hexadecanoic acid. In conclusion, the optimal solvent for extraction depends on the part of the plant material and the compounds that are to be isolated.     

Vegetational variation of phenolic compounds in Epilobium angustifolium

Epilobium angustifolium L. herbs are used in ethnomedicine to treat benign prostate hyperplasia. The aim of the study was to investigate the phenolic contents in distinct E. angustifolium organs during the whole vegetational period from May to October. The plants were obtained from a remote habitat in Estonia and spectrophotometrically analysed for the total polyphenol, tannin, and flavonoid contents. The total polyphenol content was the highest in roots (85?mg?g(-1)) and stems (67?mg?g(-1)) in July. The total flavonoid content was the highest in leaves (2.36?mg?g(-1)) and flowers (2.09?mg?g(-1)) and it remained relatively stable during the summer months. The highest tannin content was found in small growing plants in May; in older ones it declined, whereas the absolute yield per plant was greater. In sum, the aerial organs without stems collected in July-August are the best choice to get E. angustifolium plant material with stable high phenolic content.     

In vitro antioxidant,antifungal and antibacterial activities of five international Calibrachoa cultivars

The total phenolic, flavonoid and tannin contents in leaf extracts of Calibrachoa x hybrida (C.h.) (Solanaceae) international cultivars, as well as their overall antioxidant activities using DPPH and linoleic acid assays, were investigated. Furthermore, the antifungal and the antibacterial activities were examined against a wide spectrum of micro-organisms. DPPH and linoleic acid assays ranged from 62.1 to 80.1% and of 74.1–93.4%, respectively. C.h. Superbells® Trailing Rose (CHST), C.h. Superbells® Frost Fire, C.h. Superbells® Strawberry Punch, C.h. Superbells® Dreamsicle and C.h. Superbells® Plum (CHSP) varied in their antifungal and the antibacterial activities against a wide spectrum of micro-organisms. CHSP exhibited the highest antioxidant, antifungal and antibacterial activities followed by CHST. These activities might be attributed to the presence of phenolic, flavonoid and tannin compounds, indicating that these cultivars might be potential sources of therapeutic substances.     

Solvent-Induced Phase Transformations of Hydrates

An increase of the specific surface area of solid phases is often desirable e.g. for the bioavailability of pharmaceuticals or in chemical processes. Such an increase can a.o. be achieved by suspending crystalline substances in a solvent that induces phase transformations. Hence, the original substance has to be in a metastable state in the solvent. If the stable phase after transformation has in addition a very low solubility in the solvent, a dendritic growth is forced to occur because of the high local supersaturations during the phase change. This dendritic growth of the stable phase in term leads to needle- or whisker-like crystals, which have the desired larger specific surface area in comparison to the initial crystalline substance.In order to investigate this phenomenon several hydrates of salts were chosen, which undergo phase transformations to their anhydrates accompanied by a corresponding loss of crystal water when suspended in excess in lower alcohols. Consequently, anhydrous forms were created by dehydrating these hydrates. The transformation rate or in this case the dehydration level can thus be indirectly measured by Karl-Fischer titration. The thermodynamic background of the dehydration phenomena can be clarified by solubility studies of the hydrates and anhydrates in water/alcohol-mixtures.This revised version was published online in November 2005 with corrections to the Cover Date.     

黄芩中黄芩苷的亚临界水提取及高效液相色谱分析

建立了黄芩药材中黄芩苷的亚临界水提取 高效液相色谱测定方法。分别考察了温度、压力、提取时间、提取物颗粒度、溶剂比等因素对提取量的影响,并与有机溶剂提取法比较。结果表明,当两者具有相同的提取效果时,亚临界水提取法的提取时间及提取溶剂的消耗量大大减少,避免了使用有机溶剂造成的污染。黄芩苷提取最佳条件为:样品颗粒度80～100目,溶剂比0.2 mL/mg ,5 MPa,130 ℃保持10 min。并通过提取 高效液相色谱联机分析实现了对提取物的实时监测。该技术有望成为从中药材中提取脂溶性成分的有效方法。     

Simultaneous determination of solubility, dissolution and dilution enthalpies of a substance from a single calorimetric experiment

The thermodynamics of dissolution in water of a set of substances has been studied calorimetrically. The examined substances were: potassium chloride, (glycyl-glycyl)diketopiperazine, (alanyl-alanyl)diketopiperazine, (leucyl-glycyl)diketopiperazine. They were chosen on the basis of their solubilities, going from a highly soluble electrolyte to the sparingly soluble diketopiperazines. It is shown that, using a commercially available calorimeter, it is possible to perform in a single calorimetric experiment the simultaneous determination of all thermodynamic parameters characterizing dissolution of a substance in a given solvent, i.e. solubility, dissolution enthalpy and dilution enthalpy. The solubility values in water obtained through the proposed method are in good agreement with those reported in the literature and obtained by other techniques.     

A continuous preconcentration/extraction method for organic trace analysis by capillary gas chromatography

Summary A slightly modified steam distillation-extraction device is described for the continuous extraction and preconcentration of organic traces in aqueous samples, prior to capillary G.C.-analysis. The quantitative performance, both theoretically and practically, is studied using phenols as the test substances. The final recovery is determined by the flow-ratio of the water and the extracting solvent and by the extraction coefficient. The process is found to be highly reproducible even at low concentration levels (ppb’s). Using 30 ml. samples with a concentration of 30 ppb (1:10^9), 100 % recoveries are obtained for the phenolic substances studied, with a relative standard deviation of about 3 %, both for methylene chloride and ethylacetate as the extracting solvents. Using methylene chloride as the extracting solvent, for phenol a maximum recovery of 80 % was obtained. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Molecular characterisation of birch bark tar by headspace solid-phase microextraction gas chromatography-mass spectrometry: a new way for identifying archaeological glues

To develop an analytical methodology, as non-destructive as possible, suitable for the identification of natural substances from archaeological origin, we studied the potentiality of solid-phase microextraction (SPME) for analysing birch bark tar, an adhesive commonly used during ancient times. First of all, birch bark tars were produced by a controlled heating of birch bark. The two kinds of samples obtained using different processes of fabrication, one at liquid state, the second one at solid state, were then analysed by headspace HS-SPME-GC-MS. Different conditions of sample treatment were tested (two different fibre coatings, various times and temperatures of extraction) in order to suggest optimal conditions for the analysis of birch bark tar. Both samples were shown to be rich in volatile organic components. Two main groups of constituents, namely phenolic compounds issued from lignin or tannin known to be present in bark and sesquiterpenoid hydrocarbons, secondary metabolites largely distributed in the plant kingdom, were detected for the first time in birch bark tar. HS-SPME-GC-MS appears thus to be a very efficient method for investigating the volatiles emitted by plant tars and could be further used for the study of birch bark tar samples issued from archaeological context.     

Determination of phenolic compounds in wastewater by liquid-phase microextraction coupled with gas chromatography

Liquid-phase microextraction (LPME) coupled with gas chromatography-flame ionization detection is applied to the analysis of phenolic compounds (phenol, o-cresol, m-cresol, 2,4-dimethylphenol, 2,3- dimethylphenol, and 3,4-dimethylphenol) in water samples. Experimental parameters affecting the extraction efficiency (including extraction solvent and drop volume, stirring rate, extraction time, temperature, salt concentration, and pH) are investigated and optimized. The developed protocol yields a good linear calibration curve from 5 or 20 to 10000 microg/L for the target analytes. The limits of detection are in the range of 0.94 to 1.97 microg/L, and the relative standard deviation is below 9.37%. The established method is applied to determine the phenolic pollutants in real wastewater samples from a coking plant. The recoveries of the phenolic compounds studied are from 92% to 102%, suggesting the feasibility of the LPME method for the determination of the phenolic compounds in wastewater.     

Fast,easy, and efficient method for the purification of phenolic isomers using a selective solid-phase scavenging process

The need for fast and efficient purification methods that can be easily handled and moreover automated is considerably increasing with the new techniques of high-throughput chemical synthesis. Following our previous work on the use of simple polymeric scavengers in fast reactions and purifications of organic substances, this article presents the results found during the development of a new method for the purification of phenolic substances. The purification method was found to be regulated by the interaction of acidic phenol groups with a basic polystyrene resin. Furthermore, the scavenging of phenolic isomers proved to be very selective for a given isomer. But the most interesting aspect of this method is that it is based on a simple contact in situ with the resin and that the adsorption/desorption process of the phenol was found to be solvent-dependent. The phenols can thus be freed from impurities, or other isomers, by a simple and fast contact with the resin in the first solvent, filtration, and washings, followed by liberation of the purified phenol by a last soaking in another solvent for desorption. The method was successfully applied to the purification of a crude reaction mixture issued from the Fries rearrangement of phenyl acetate, as well as to small libraries of phenolic derivatives.     

Metal-modified silica adsorbents for removal of humic substances in water

As novel adsorbents for humic substances, Fe-, Mg-, and Ca-modified silica gels SiO(2)Fe, SiO(2)Mg, and SiO(2)Ca were prepared, and their adsorbabilities to humic and fulvic acids were evaluated in water at 25 degrees C for 20 h. Among these adsorbents, SiO(2)Fe indicated the highest adsorbability, in which removing humic substances in water was accomplished to 80-97%. By calcination at 600 degrees C and washing with water, adsorbabilities of the silica adsorbents deteriorated except for the case of calcination of SiO(2)Ca. This is due to changing metal modification structures and losing chlorine, judging from elemental analysis, TG-DTA, and XPS. Especially, the modifier Fe was tightly fixed on the silica surface of SiO(2)Fe, since the metal content was almost constant even after the calcination and water washing unlike the other adsorbents. Therefore, we found that SiO(2)Fe is the most useful adsorbent among the silica adsorbents and that its modification structure is composed of SiOFe, FeCl, and FeOH. In addition, the adsorption mechanism is explained by an interaction between Fe and humic substance molecule having carboxylate and phenolate groups, accompanied with anion exchange of chloride ion Cl(-) for the humic substance molecule via the silica pores. SiO(2)Fe may be applied to an adsorbent alternative for charcoal in water purification plants, and the used SiO(2)Fe may be further reused as a fertilizer since humic substances have plant-glowing ability and silica strengthens plant parts.     

Effect of organic co-solvents on the solvation enthalpies of amino acids and dipeptides in mixed aqueous solutions

Transition enthalpies (Δ_tr H ^o) of substances from water to binary solutions were calculated at 298.15 K on the basis of standard dissolution enthalpies (Δ_sol H ^o) for six amino acids and five dipeptides in the mixtures of water with organic solvents of various chemical natures. The enthalpy pair coefficients of interaction h _xy for biomolecules with organic component of mixture were estimated within the formalism of the McMillan-Mayer theory. The change in the character of the interaction of the components of solution was demonstrated in dependence on the physicochemical properties of the solvent and nature of the side radical of the dissolved bioorganic substance. Quantitative estimation of the type of interaction of the substance with the solvent was performed on the basis of correlation ratios relating the enthalpy characteristics of bioorganic substances to properties of organic cosolvents. It was shown that in the solutions under study, the effects of both the specific (mainly electron donor) and non-specific solvation of amino acids and peptides are observed.     

Solvent Mixture Optimization in the Extraction of Bioactive Compounds and Antioxidant Activities from Garlic (Allium sativum L.)

Garlic is a health promoter that has important bioactive compounds. The bioactive extraction is an important step in the analysis of constituents present in plant preparations. The purpose of this study is to optimize the extraction with the best proportion of solvents to obtain total phenolic compounds (TPC) and thiosulfinates (TS) from dried garlic powder, and evaluate the antioxidant activities of the optimized extracts. A statistical mixture simplex axial design was used to evaluate the effect of solvents (water, ethanol, and acetone), as well as mixtures of these solvents, after two ultrasound extraction cycles of 15 min. Results showed that solvent mixtures with a high portion of water and pure water were efficient for TPC and TS recovery through this extraction procedure. According to the regression model computed, the most significant solvent mixtures to obtain high TPC and TS recovery from dried garlic powder are, respectively, the binary mixture with 75% water and 25% acetone and pure water. These optimized extracts presented oxygen radical absorbance capacity. Pure water was better for total antioxidant capacity, and the binary mixture of water–acetone (75:25) was better for DPPH scavenging activity. These optimized extracts can be used for industrial and research applications.     

Determination of volatile amines in drug substances by capillary gas chromatography

The determination of small, water soluble amines such as aziridine and 2-chloroethylamine, in drug substances at trace levels is described. After removal of the bulk of the drug substance by extraction or precipitation, derivatization with acid chlorides is performed. In a two-phase (water-organic solvent) system, this derivatization reaction is accomplished almost simultaneously with the extraction of the product to the organic layer. The organic layer is analyzed by gas chromatography using on-column injection and selective detection. Detection limits are approx. 0.2 mg/kg for aziridine and approx. 0.5 mg/kg for 2-chloroethylamine.     

A comparative study of upright counter-current chromatography and high-performance liquid chromatograpohy for preparative isolation and purification ofphenolic compounds from Magnoliae officinalis

A comparative study of preparative isolation and purification of the phenolic compounds magnolol and honokiol from the Chinese medicinal plant Magnoliae officinalis by upright counter-current chromatography (CCC) and semi-preparative HPLC is presented. The comparison reveals that with a two-phase solvent system composed of light petroleum (bp 60-90 degrees C)-ethyl acetate-tetrachloromethane-methanol-water (1:1:8:6:1, v/v), 1250 mg of honokiol and 520 mg of magnolol, with a purity of 98.7 and 99.5%, respectively, were obtained from 2.0 g of a crude sample of Magnoliae officinalis in a single CCC separation. In contrast, semi-preparative HPLC allowed isolation and purification of these two phenolic compounds with significantly lower productivity and higher solvent consumption. Structures of the purified compounds were identified by 1H and 13C NMR.     

Antioxidant activities and polyphenolic contents of three selected Micromeria species from Croatia

Antioxidant activities of three selected Micromeria species growing in Croatia (M. croatica, M. juliana and M. thymifolia) were evaluated using five different antioxidant assays, in comparison with plant polyphenolic constituents and reference antioxidants. All studied ethanolic extracts exhibited considerable activity to scavenge DPPH and hydroxyl free radicals, reducing power, iron chelating ability and total antioxidant capacity in the order: M. croatica > M. juliana > M. thymifolia. Total polyphenol (9.69-13.66%), phenolic acid (5.26-6.84%), flavonoid (0.01-0.09%) and tannin (3.07-6.48%) contents in dried plant samples were determined spectrophotometrically. A strong positive correlation between antioxidant activities and contents of phenolic acids and tannins was found, indicating their responsibility for effectiveness of tested plants. Our findings established Micromeria species as a rich source of antioxidant polyphenols, especially the endemic M. croatica.     

A hydrolyzable tannin substance from the fruit ofRosa platyacantha

A new hydrolyzable tannin substance has been isolated from an anqueous hydrolysate of an aqueous-acetone extract of the fruit ofRosa platyacantha — 1-dehydrotrigalloyl-α-D-glucose — and it has been named platyacanthin. The substance is a minor component of the tannin complex.     

Enthalpies of solution of paracetamol and sodium diclofenac in phosphate buffer and in DMSO at 298.15 K

We have been using a heat conduction microcalorimeter to measure enthalpies of dissolution of slightly soluble solids. Recently we did report the testing of the prototype and we are now extending the previous investigation to measurements with organic solvents.In the present work we use DMSO due to its importance in the pharmaceutical industry. The importance of the applications of enthalpies of solution in organic solvents calls for the need to find a substance that can be used in the future for chemical calibration in these solvents. Attempts for proposing such a substance have also been a goal for our research group.The enthalpies of solution of paracetamol and sodium diclofenac were measured in DMSO and in phosphate buffer (pH 6.91) at 298.15 K. We show that it is possible to obtain very good results with DMSO as solvent for these two drugs on our dissolution microcalorimeter. Nevertheless, due to their slow and low enthalpy of dissolution in this solvent, they cannot be seen as good candidates for test substances.