Huaifang Guo

Shandong University, Jinan, Shandong Sheng, China

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Publications (5)14.83 Total impact

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    ABSTRACT: Bioactivity-guided separation of an antifungal extract from the liverwort Asterella angusta afforded four bis(bibenzyl)s, asterelin A (1), asterelin B (2), 11-O-demethyl marchantin I (3), and dihydroptychantol A (4), together with six known ones. Their structures were established by extensive spectroscopic analysis (1D and 2D-NMR, MS), and that of 2 was confirmed by X-ray crystallographic diffraction analysis. Compounds 1 and 2 are the first examples of dibenzofuran bis(bibenzyl)s. The antifungal activity of the isolated bis(bibenzyl)s against the common clinical pathogenic fungus Candida albicans was evaluated using both the thin-layer chromatography bioautographic assay and the broth microdilution method. They showed moderate antifungal activities with minimal inhibitory concentration (MIC) values ranging from 16 microg/ml to 512 microg/ml.
    Phytochemistry 08/2007; 68(13):1767-74. · 3.35 Impact Factor
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    ABSTRACT: A cycloartane-type triterpenoid (1), an aliphatic alcohol glycoside (2), an eudesmane-type sesquiterpenoid (3), and a guaiane-type sesquiterpenoid (4) were isolated from the resinous exudates of Commiphora opobalsamum along with six known sesquiterpenoids (5-10). Their structures were established by extensive analysis of their 1D and 2D NMR spectroscopic data and chemical methods. The isolated compounds 1-3 and 5-9 were tested against human prostate cancer cell PC 3 and LNCaP. Among them, 1 and 2 showed moderate antiproliferative effects on human prostate cancer cell lines with IC50 values ranging from 5.7 to 23.6 microM; they were also able to inhibit the expression of androgen receptor (AR) in LNCaP cells. The six sesquiterpenoids were inactive in the bioassays.
    Phytochemistry 06/2007; 68(9):1331-7. · 3.35 Impact Factor
  • Yu Du, Huaifang Guo, Hongxiang Lou
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    ABSTRACT: Grape seed extract (GSE) has been reported to exert protective effects on various forms of cardiac disorders. The cardiovascular protective effects of GSE are believed to be ascribed to its antioxidative properties. A series of studies have demonstrated that polyphenols are instrumental for the antioxidative properties of GSE. This study was undertaken to investigate whether two major polyphenols isolated from GSE (catechin and proanthocyanidin B4) could increase the endogenous antioxidant enzymes in cardiomyocytes, and whether such increased cellular defenses could provide protection against oxidative cardiac cell injury. Incubation of cardiac H9C2 cells with micromolar concentrations of catechin or proanthocyanidin B4 resulted in a significant induction of cellular antioxidant enzymes in a concentration-dependent fashion. Furthermore, catechine or proanthocyanidin B4 pretreatment led to a marked reduction in xanthine oxidase (XO)/xanthine-induced intracellular reactive oxygen species (ROS) accumulation and cardiac cell apoptosis. These results indicated that grape seed polyphenols (GSP) could protect against cardiac cell apoptosis via the induction of endogenous antioxidant enzymes. This may be an important mechanism underlying the protective effects of GSE observed with various forms of cardiovascular disorders.
    Journal of Agricultural and Food Chemistry 04/2007; 55(5):1695-701. · 3.11 Impact Factor
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    ABSTRACT: A simple and rapid qualitative liquid chromatography-diode-array detection/tandem mass spectrometry (LC-DAD/MS/MS) method was developed and validated for screening bisbibenzyl compounds in bryophyte crude extracts at sub-ppm levels. After simple extraction with ethanol and analyte concentration with diethyl ether, the extracts were subjected to LC-DAD/MS/MS analysis. The overall instrument turnaround time was 50 min to obtain baseline separation of bisbibenzyl isomers in bryophytes. MS full scan, MS/MS precursor ion scan and MS/MS product ion scan modes were used for the screening. The bisbibenzyl standards studied gave limits of detection (LODs) at or below 10 ng/mL. The results also indicated that the method had acceptable precision to be used on a day-to-day basis for qualitative identification. The bisbibenzyl types, i.e. one biphenyl ether bond (A-type), two biphenyl ether bonds (B-type), one biphenyl ether and one biphenyl bond (C-type), or other biphenyl types can be differentiated by their ESI-MS/MS product profiles, and the number of alkoxyl substituents can also be identified. The linkage sites of biphenyl and biphenyl ether bonds cannot be identified for an unknown bisbibenzyl solely from its mass spectra. This system was used to support three screening assays of bryophytes including Marchantia polymorpha L., Ptagiochasm intermedium L. and Asterella angusta, which were collected from different places in China. From them, 7/12, 8/5 and 8/9 confirmed/unconfirmed bisbibenzyls were identified, respectively, based on their MS/MS data, UV spectra and the retention behavior. The screening method considerably reduced the time and the cost for the qualitative analyses, and the structure-fragmentation-UV relationships will facilitate the high-throughput screening (HTS) of bisbibenzyl compounds in bryophytes. It is also intended as a simple and convenient way for the determination of other structural families of natural products.
    Rapid Communications in Mass Spectrometry 02/2007; 21(15):2467-76. · 2.51 Impact Factor
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    ABSTRACT: A detailed analysis of mass spectra generated from bis(bibenzyl) compounds in bryophytes under electron ionization time-of-flight (EI-TOF) and electrospray ionization triple-quadrupole (ESI-TQ) mass spectrometry conditions is reported. Proposed structures of the fragment ions were obtained by tracking the functional groups of 15 bis(bibenzyls), the structures of which are similar except for some alkoxyl substituents and linkage sites of biphenyl ether bonds. The elucidation was aided by the use of accurate mass measurements. Attempts have been made to provide rational pathways for the formation of these fragment ions, and a generalized fragmentation mechanism is proposed. The bis(bibenzyls) mentioned in this study include three types according to their structure characteristics, i.e. one biphenyl ether bond (A-type), two biphenyl ether bonds (B-type), one biphenyl ether and one biphenyl bond (C-type). The three types display different EI-MS and ESI-MS/MS product profiles, by which the bis(bibenzyl) type and the number of alkoxyl substituents can be identified. Isomers of bis(bibenzyls) can be differentiated to some extent, while the linkage sites of biphenyl ether bonds are difficult to identify. The structure-fragmentation relationships will facilitate the characterization of other bis(bibenzyls) and this will be of value for the high-throughput screening of novel bis(bibenzyls) in bryophytes.
    Rapid Communications in Mass Spectrometry 02/2007; 21(8):1367-74. · 2.51 Impact Factor