Intramolecular hydrogen bonding and calixarene-like structures in p-cresol/formaldehyde resins

The nature of the strong hydrogen bonds found in p-cresol/formaldehyde (PCF) resins, compared to ordinary phenolic compounds, is studied. The evidence from FTIR spectroscopy indicates that this strong interaction is due to intramolecular hydrogen bonding from “calixarene-like” structures. The formation of this structure in PCF is enabled by its “linear” (all-ortho-linkage) structure, which is not present in branched resins. Additionally, a transition is observed at around 175 to 200°C where the intramolecular hydrogen bonded structure is lost. This structure cannot be recovered upon cooling or annealing due to restrictions on conformational rotations that are coupled to a new pattern of intermolecular hydrogen bonding. However, the structure is reformed by dissolving the resin in solution and casting new films.     

Chemical constituents from Schisandra sphenanthera

The chemical constituents of the stems of Schisandra sphenanthera are described for the first time. This investigation has resulted in the isolation of a new phenolic glycoside （1）, along with seven known compounds. The structure of 1 was assigned by using spectroscopic techniques, including 2D NMR spectra.     

Structure elucidation and complete NMR spectral assignments of new furostanol glycosides from Solanum torvum

Two new furostanol glycosides, torvosides O (1) and P (2), were isolated from leaves of Solanum torvum. Their structures were completely and unambiguously assigned by one‐ and two‐dimensional NMR techniques (¹H NMR, ¹³C NMR, TOCSY, HSQC, ROESY and HMBC), ESI‐MS spectrometry and chemical methods. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of Synthetic Phenolic Antioxidants in Vegetable Oil and Oil-Enriched Foods by High-Performance Liquid Chromatography with Electrochemical Detection

Three synthetic phenolic antioxidants, tertiary butyl hydroquinone, butylated hydroxytoluene, and butylated hydroxyanisole, were determined in vegetable oil and oil-enriched food by high-performance liquid chromatography (HPLC) with electrochemical detection. The separation was achieved using a reverse-phase column and gradient elution with methanol and 1% acetic acid. The limits of detection and quantification of the analytes were 2–120 lower, higher than those obtained by diode-array detection. The recoveries were 103.3% for tertiary butyl hydroquinone, 97.3% for butylated hydroxyanisole, and 95.2% for butylated hydroxytoluene. The results showed that HPLC with electrochemical detection is suitable for the quantification of low concentrations of phenolic antioxidants in vegetable oil and oil-enriched food with high sensitivity and accuracy.     

橡胶及橡胶制品中4种酚类防霉剂的高效液相色谱法测定

建立了橡胶及其制品中硝基苯酚(PNP)、2,3,5,6-四氯苯酚(TeCP)、五氯苯酚(PCP)、邻苯基苯酚(OPP)4种酚类防腐剂的高效液相色谱测定方法。样品冷冻粉碎后,经甲醇超声提取,在Venusil-XBP C18色谱柱(250 mm×4.6 mm,5μm)上以10 mmol/L醋酸铵和甲醇为流动相梯度洗脱,采用二极管阵列检测器,PCP、TeCP、OPP的检测波长为220 nm,PNP的检测波长为320 nm。4种酚类防霉剂的质量浓度在0.5~250mg/L范围内与峰面积呈良好的线性关系,相关系数大于0.999 4。丁苯橡胶、硅橡胶基体的加标回收实验结果表明:TeCP、PCP、OPP、PNP在不同基质中的平均加标回收率分别为82%~95%、68%~90%、85%~98%、87%~98%,相对标准偏差小于5%。     

A New Triterpenoid Glycoside from Decaisnea Fargesii

Deculsnea./al..gesiiFranch.IsatraditionalChinesemedicinalplantwidely'distributedinChina.usedasananti-rheumaticandalltitussivedrugforalongtimeinChinesefolkmedicine'.Itsmethanolextractshowedantitunlouracidityif71)if)oagainstS:sl},HepaandEhrlichcellsanditsphytochemicalstudiesonsaponinshasreported'.Asacontinuationofthestudiesonthisplant,wepresentthespectralandchemicalevidenceofthestructureofanewdecaisosideF.Thedriedstems(2.23kg)werepercolated\vith95%EtOH.Afterremovalofthepercolatesb}evaporat…     

Sulfated steroid glycosides from the Viet Namese starfish <Emphasis Type="Italic">Linckia laevigata</Emphasis>

Five sulfated steriodal compounds including one new glycoside called linckoside L7 (1) and four previously known glycosides 2–5 were isolated from the starfish Linckia laevigata. The structure sodium (22E, 24R)-3-O-(2-O-methyl-β-D-xylopyranosyl)-29-O-(β-D-xylopyranosyl)-24-ethylcholest-4,22-dien-3β,6β,8,15α,16β,29-hexaol 15-O-sulfate was proposed for L7. Linckoside L7 inhibited fertilization and egg-cell development in the sea urchin Strongylocentrotus intermedius. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 64–67, January–February, 2007.     

Total assignment of 1H and 13C NMR spectra of three triterpene saponins from roots of Silene vulgaris (Moench) Garcke

The assignments of ¹H and ¹³C NMR spectra for three new triterpene saponins from Silene vulgaris (gypsogenin 3‐O‐glucuronide, quillaic acid 3‐O‐glucuronide, and gypsogenin 3‐O‐glycoside) are reported. In addition to 1D NMR methods, 2D NMR techniques (COSY, HSQC, HMBC, and HSQC‐TOCSY) were used for the assignments. Copyright © 2002 John Wiley & Sons, Ltd.     

Evaluation of antioxidant activities of the edible and medicinal Acacia albida organs related to phenolic compounds

This study compared phenolic contents and antioxidant activity in different organs of Acacia albida (leaves and bark) and focuses on identification of phenolic compounds of leaves by HPLC-DAD. The analysed organs exhibited differences in total polyphenol contents (100 and 59.5 mg GAE g^? 1 DW). Phenolic contents of leaves were two times higher than those in bark. Ethanolic extracts exhibited good antioxidant activities with IC₅₀ = 26 μg mL^? 1 for DPPH and EC₅₀ = 50 μg mL^? 1 for FRAP. Identification by HPLC-DAD revealed the presence of nine phenolic compounds known for their high antioxidant activity. The results suggested that this species can be used as source of natural antioxidants.