Xuefeng Guo

9, 10-Dihydrophenanthrene derivatives from Pholidota yunnanensis and scavenging activity on DPPH free radical

Three new 9,10-dihydrophenanthrene derivatives named phoyunnanins A–C, together with six known 9,10-dihydrophenanthrene constituents, 4,4′,7,7′-tetrahydroxy-2,2′-dimethoxy-9,9′,10,10′-tetrahydro-1,1′-biphenanthrene (4), lusianthridin (5), eulophiol (6), 2,4,7-trihydroxy-9,10-dihydrophenanthrene (7) and imbricatin (8), were isolated from the 60% ethanolic extract of air-dried whole plant of Pholidota yunnanensis Rolfe. The structures of phoyunnanins A–C were established as 6-[2′-(3′,3″-dihydroxy-5′-methoxybibenzy)]-4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (1), 6-[6′-(trans-3′,3″-dihydroxy-5′-methoxystilbeny)]-4,7-dihydroxy-2-methoxy-9,10-dihydrophenanthrene (2) and 4,4′,7,7′-tetrahydroxy-2,2′-dimethoxy-9,9′,10,10′-tetrahydro-1,6′-biphenanthrene (3), respectively, on the basis of the spectroscopic analysis. All eight compounds (1–8) were found to show the DPPH free radical scavenging activity with EC50 from 8.8 to 55.9 μM.

FLAVONOIDS FROM THE LEAVES OF Neosinocalamus affinis

Nine flavonoids were isolated from the dry leaves of Neosinocalamus affinis (Rendle) Keng f. The flavonoid structures were determined by spectroscopy using UV, 1D and 2D NMR, and MS. Two new C-glycosyl flavones, tricin-6-C-β-boivinopyranosyl-8-C-β-glucopyranoside (1) and 5,7,4′-trihydroxy-3′-methoxy-6-C[β-D-xylopyranosyl-(1 → 2)]-β-D-glucopyranosyl flavonoside (4), were found in addition to seven known flavonoids, apigenin-6-C-β-boivinopyranosyl-7-O-β-glucopyranoside (2), luteolin-6-C-β-boivinopyranosyl-7-O-β-glucopyranoside (3), isovitexin-2″-xyloside (5), isoorientin-2″-xyloside (6), tricin-7-O-β-glucopyranoside (7), isoorientin (8), and tricin (9). This is the first reported isolation of these flavonoids from N. affinis.

Simultaneous HPTLC analysis of flavonoids in the leaves of three different species of bamboo

Flavonoids are the main functional compounds in a bamboo leaf extract. Because of their activity flavonoids are widely used in many of health products, cosmetics, and food supplements. A simple highperformance thin-layer chromatographic (HPTLC) method has been established for simultaneous quantification of vitexin, isovitexin, orientin, and isoorientin in the leaves of three different bamboo species: Phyllostachys pubescens Mazel ex H. de Lehaie, Phyllostachys glauca McClure, and Pleioblastus yixingensis S. L. Chen et S. Y. Chen. The method was validated for precision (expressed as the coefficient of variation, CV [%]), accuracy, sensitivity, and selectivity. Instrumental precision was found to be 0.37, 0.52, 0.39, 0.13, and 0.84% and the repeatability of the method 0.98, 0.91, 1.02, 1.04 and 0.87% for isovitexin, rutin, orientin, isoorientin, and vitexin, respectively. The accuracy of the method was determined by measurement of recovery at three different concentrations. Average recovery was 99.54% for isovitexin, 99.31% for orientin, and 100.55% for isoorientin from P. pubescens; 98.97% for orientin, 99.00% for isovitexin, and 99.58% for vitexin from P. glauca; and 98.86% for orientin, 100.04% for isoorientin, and 99.63% for vitexin in P. yixingensis, In the fraction extracted from bamboo leaves known as Flavone Gruff the flavonoid content was 6.44% (w/w) for orientin, 3.45% for isovitexin, and 6.58% for isoorientin in P. pubescens; 7.82% for orientin, 2.82% for isovitexin, and 13.7% for vitexin in P. glauca; and 4.92% for orientin, 3.50% for isoorientin, and 22.5% for vitexin in P. yixingensis. Although the presence of rutin was confirmed in the bamboo leaves investigated, it could not be quantified because of its low concentration. The proposed HPTLC method was found to be simple, precise, selective, sensitive, and accurate for routine quality control of the leaves of different bamboo species and formulations containing bamboo-leaf flavonoids.

Two new compounds from the dry leaves of Pleioblastus amarus (Keng) keng f.

Two new compounds, xylitol 1-O-(6′-O-p-hydroxylbenzoyl)-glucopyranoside (1) and bambulignan B (2), together with three known ones gastrodin (3), glucovanillin (4), and rel-(7S,7′R,8R,8′S)-4,4′-dihydroxy-3,3′,5,5′-tetramethoxy-7,7′-epoxyligna-9,9′-diol-9(or)9′-O-β-glucopyranoside (5), were isolated from the 95% EtOH extract of the dry leaves of Pleioblastus amarus (Keng) keng f. Their structures were determined by UV, IR, HR-ESI-MS, CD, and 1D and 2D NMR data analyses as well as GC experiments.

Coumarins from the leaves of Bambusa pervariabilis McClure

A new pyrone-coumarin, 7,8-dihydroxy-3-(3-hydroxy-4-oxo-4H-pyran-2-yl)-2H-chromen-2-one (1), along with two known coumarins, scopoletin (2) and scopolin (3), was isolated from the 95% EtOH extract of the leaves of Bambusa pervariabilis McClure. Their structures were determined on the basis of spectroscopic techniques and chemical methods.

Flavonoids from the leaves of Pleioblastus argenteastriatus

A new flavonoid, 5,7,3′-trihydroxy-6-C-β-d-digitoxopyranosyl-4′-O-β-d-glucopyranosyl flavonoside (1), along with four known flavonoids 5,7,4′-trihydroxy-3′,5′-dimethoxy flavone (2), 5,3′,4′-trihydroxy-7-O-β-d-glucopyranosyl flavonoside (3), 5,4′-dihydroxy-3′,5′-dimethoxy-7-O-β-d-glucopyranosyl flavonoside (4), 5,3′,4′-trihydroxy-6-C-[β-d-glucopyranosyl-(1 → 6)]-β-d-glucopyranosyl flavonoside (5) were isolated from 95% EtOH extract of the leaves of Pleioblastus argenteastriatus. Their structures were determined on the basis of spectroscopic techniques and chemical methods.

Two new compounds from the leaves of Indocalamus latifolius

Abstract Two new compounds, erythro-syringylglycerol-9-O-trans-4-hydroxycinnamate 7-O-β-d-glucopyranoside (1) and indocalatin A (2), together with three known ones, 5,7,3′-trihydroxy-6-C-β-d-digitoxopyranosyl-4′-O-β-d-glucopyranosyl flavonoid (3), 5,4′-dihydroxy-3′,5′-dimethoxy-7-O-[β-d-apiose-(1→2)]-β-d-glucopyranosyl flavonoid (4), and tricin-6-C-β-boivinopyranosyl-8-C-β-glucopyranoside (5), were isolated from the 95% EtOH extract of Indocalamus latifolius leaves. Their molecular structures were determined by UV, IR, HRESIMS, CD, and 1D and 2D NMR data analyses.

Chemical Constituents and Antibacterial Properties of Indocalamus latifolius McClure Leaves, the Packaging Material for “Zongzi”

The glutinous rice dumpling named “Zongzi” in Chinese is a type of traditional food that is popular in East Asian countries. “Zongzi” is made of glutinous rice and wrapped in the leaves of Indocalamus latifolius McClure as the packaging material. Four new compounds, latifoliusine A (2), (7S,8R) syringylglycerol-8-O-4′-sinapyl ether 4-O-β-d-glucopyranoside (7), (7S,8S) syringylglycerol-8-O-4′-sinapyl ether 7-O-β-d-glucopyranoside (8), and (7R,8S) syringylglycerol-8-O-4′-sinapyl ether 7-O-β-d-glucopyranoside (10), along with six known compounds (1, 3–6 and 9) were isolated from I. latifolius McClure leaves. The structures and relative configurations of the compounds were determined by detailed spectroscopic analysis, high-resolution electrospray ionization mass spectroscopy (HRESIMS), heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear overhauser enhancement (NOE) and circular dichroism (CD). All of the isolated compounds were screened for their antibacterial activities in vitro. The results indicated that apigenin 6-C-α-l-arabinopyranosyl-8-C-β-d-glucopyranoside (5) and apigenin 7-O,8-C-di-glucopyranoside (6) have antibacterial activities against four bacterial strains (Staphylococcus aureus, Bacillus thuringiensis, Escherichia coli and Pseudomonas solanacearum).

Optimization of carbamylation conditions and study on the effects on the product ions of carbamylation and dual modification of the peptide by Q-TOF MS

Modified peptides fragmented by collision-induced dissociation can offer additional sequence information, which is beneficial for the de novo sequencing of peptides. Here, the model peptide VQGESNDLK was carbamylated. The optimal conditions were as follows: temperature of 90℃, pH of 7, and the time of 60 min. Then, we studied the b- and y-series ions of the native, carbamylated, and dual-modified peptides. The results were as follows. The short carbamylated peptides (≤10 amino acid residues) produced more b-series ions (including b1 ion). The long carbamylated peptides (>10 amino acid residues) produced additional b1 ion but fewer y-series ions (especially in the high-mass region). The short dual-modified peptides produced more b-series ions (including b1 ion) and more y-series ions, and their peptide sequence coverage was almost 100%. The long dual-modified peptides produce b1 ion and more y-series ions, and their peptide sequence coverage was nearly above 90%. Therefore, both carbamylation and the dual modification method could be used to identify the N-terminal amino acid, and the dual modification method was also excellent for the de novo sequencing of the tryptic peptides.

Fragmentation Characterization and Differentiation of Isomeric Diglycosyl Flavonoids Using Ultra-High-Performance Liquid Chromatography Electrospray Ionization Quadrupole Time-of-Flight Tandem Mass Spectrometry in Negative Ion Mode:

Flavonoids exhibit a wide range of biological activities and the fragmentation characterization and differentiation of isomeric diglycosyl flavonoids is an important area of research. In this study, ultra-high-performance liquid chromatography electrospray ionization quadrupole time-of-flight tandem mass spectrometry was used to identify two pairs of isomeric diglycosyl flavonoids: naringin/narirutin and neohesperidin/hesperidin. The two pairs of flavonoids were identified by product ion tandem mass spectra of the precursor ions [M – H]−. The results showed that characteristic product ions distinguishing flavonoids glycosylated with rhamnosyl-(α1 α 2)-glucosyl from isomeric flavonoids glycosylated with rhamnosyl-(α1 α 6)-glucosyl were the precursor ion [M – H]− and its characteristic product ions Y0− and [0,2X0 – H]−.