Hua-Yi Qi

Nitrogen-Containing Dihydro-β-agarofuran Derivatives from Tripterygium wilfordii

Thunder god vine, the dried roots of Tripterygium wilfordii, is a widely used traditional Chinese medicine. More than 200 bioactive complex natural products have been isolated from this herb. Inspired by the diversity of chemical structures and bioactivities of the components of this herb, the investigation to mine new chemical entities as potential drug leads led to the identification of 36 nitrogen-containing compounds. Among them, 18 new dihydro-β-agarofuran alkaloids (tripterygiumines A-L (1-12), M-Q (22-26), and R (33)) were identified from the spectroscopic data and chemical degradation studies. Tripterygiumine Q (26) exhibited immunosuppressive activity against human peripheral mononuclear cells with an IC50 value of 8.67 μM and showed no cytotoxicity, even at 100 μM, indicating that 26 may represent a novel scaffold for the development of new immunosuppressants.

Analysis of phenolic glycosides from Ilex litseaefolia using electrospray ionization quadrupole time-of-flight mass spectrometry.

Figure 1. Phenolic glycosides: 3-hydroxy-4-O-b-D-(6-Oacetylglucopyranosyl)benzyl vanilloate (litseaefoloside A (1), Mr 494.1424); 3-hydroxy-4-O-b-Dglucopyranosylbenzyl vanilloate (vanilloylcalleryanin (2), Mr 452.1319); 4-O-b-Dglucopyranosylbenzyl vanilloate (3, Mr 436.1369); 3-hydroxy4-O-b-D-(6-O-caffeoylglucopyranosyl)benzyl vanilloate (litseaefoloside C (4), Mr 614.1636); 3-hydroxy-4-O-b-D-(6-Ovanilloylglucopyranosyl)benzyl vanilloate (litseaefoloside D (5), Mr 602.1636); 4-O-b-D-(6-O-vanilloylglucopyranosyl)vanillic acid (6, Mr 480.1268). Dear Editor,

Analysis of caffeic acid derivatives from Osmanthus yunnanensis using electrospray ionization quadrupole time-of-flight mass spectrometry.

A series of six caffeic acid derivatives (1–6) in Osmanthus yunnanensis were investigated by electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QToF-MS/MS) in both negative- and positive-ion modes. High-quality MS/MS spectra of [M + H]+ are generated from high-abundance protonated parent ions obtained by addition of ammonium chloride to the solutions. Fragmentation mechanisms of [M – H]− and [M + H]+ precursor ions were proposed and elemental compositions of most of the product ions were confirmed on the basis of the high-resolution ESI-collision-induced dissociation (CID)-MS/MS spectra. It was found that the fragment ions at m/z 179, m/z 161, m/z 135 and m/z 134 in negative-ion mode and at m/z 163, m/z 145 and m/z 135 in positive mode should be the characteristic ions of caffeic acid. In addition, the radical fragment ions with high abundance were observed for many caffeic acid derivatives especially for 4. The structural elements of unknown compounds 7 and 8 were tentatively identified on based on tandem mass spectra of known ones.

Steryl esters and phenylethanol esters from Syringa komarowii

Three new steryl esters and a new phenylethanol ester, together with 22 known compounds were isolated from the aqueous ethanolic extract of the whole plants of Syringa komarowii. The new compounds were elucidated as stigmastane-3beta,6alpha-diol 3-O-tetradecanoate (1), stigmastane-3beta,6alpha-diol 3-O-palmitate (2), stigmastane-3beta,6alpha-diol 3-O-stearate (3), and 2-(4-hydroxyphenyl)-ethyl dotriacontanoate (4) on the basis of extensive spectral data and chemical evidences.

Analysis of a caffeic acid derivative by ESI–MS/MS: unexpected product ions formed by ‘internal residue loss’

Oxidation reactions are of major significance in human physiology, and oxidation stress is believed to be an important contributing factor to the pathology of atherosclerosis, cancer and tissue damage in rheumatoid arthritis. There is currently an intense research interest regarding phenolic compounds in the fields of food and medicine due to their free radical scavenging activity. Caffeic acid derivatives are a kind of important phenolic acid compounds. It is necessary to develop a rapid and sensitive method for the analysis of these compounds. Recently, the application of electrospray ionization mass spectrometry (ESI–MS) or highperformance liquid chromatography (HPLC)/ESI–MS has been reported to analyze the caffeic acid derivatives. Herein, a caffeic acid derivative, 4-(6-O-caffeoyl-β-D-glucopyranosyloxy)-5hydroxyprenyl caffeate, was investigated by ESI–quadrupole time-of-flight tandem mass spectrometry (QTOF). Structural information provided by ESI–MS is obtained by fragmentation reactions. ‘Internal residue loss’ is an interesting fragmentation reaction, which can provide characteristic structural information. The reaction occurs with losses of residues from inside the parent molecule rather than from the ends of the molecule. The processes of ‘internal residue loss’ might involve an important ion–neutral complex intermediate, in which the incipient ionic and neutral fragments maintain interactions with each other in the gas phase. In this paper, we found that ‘internal residue loss’ plays an important role in the fragmentation of 4-(6-O-caffeoyl-β-D-glucopyranosyloxy)-5hydroxyprenyl caffeate.

A new glucoceramide from the watermelon begonia, Pellionia repens

A new glucoceramide named pellioniareside (1) was isolated from the aqueous ethanolic extract of whole plants of Pellionia repens, together with lupeol (2), uracil (3), (22E,20S,24R)-5α,8α-epidioxyergosta-6,22-dien-3-β-ol (4), and daucosterol (5). The structure and relative configurations of pellioniareside were identified as (2S,3S,4R,6E,8E)-1-O-β-d-glucopyranosyl-2-[(2R)-2-hydroxytetracosanoylamino]-1,3,4-octadecanetriol-6,8-diene by analysis of spectral data and by chemical evidence.

Analysis of sesterterpenoids from Aspergillus terreus using ESI-QTOF and ESI-IT.

INTRODUCTION Biosynthesis of terretonin was studied due to the interesting skeleton of this series of sesterterpenoids. Very recently, López-Gresa reported two new sesterterpenoids (terretonins E and F) which are inhibitors of the mammalian mitochondrial respiratory chain. Mass spectrometry (MS), especially tandem mass spectrometry, has been one of the most important physicochemical methods for the identification of trace natural products due to it rapidity, sensitivity and low levels of sample consumption. The potential application prospect and unique skeleton prompted us to study structural characterisation using MS. OBJECTIVE To obtain sufficient information for rapid structural elucidation of this class of compounds using MS. METHODOLOGY The elemental composition of the product ions was confirmed by low-energy ESI-CID-QTOF-MS/MS analyses. The fragmentation pathways were postulated on the basis of ESI-QTOF-MS/MS/MS and ESI-IT-MS(n) spectra. Common features and major differences between ESI-QTOF-MS/MS and IT-MS(n) spectra were compared. For ESI-QTOF-MS/MS/MS experiments, capillary exit voltage was raised to induce in-source dissociation. Ammonium acetate or acetic acid were added into solutions to improve the intensity of [M + H]+. The collision energy was optimised to achieve sufficient fragmentation. Some fragmentation pathways were unambiguously proposed by the variety of abundance of fragment ions at different collision energies even without MS(n) spectra. RESULTS Fragmentation pathways of five representative sesterterpenoids were elucidated using ESI-QTOF-MS/MS/MS and ESI-IT-MS(n) in both positive- and negative-ion mode. The key group of characterising fragmentation profiles was ring B, and these fragmentation patterns are helpful to identify different types of sestertepenoids. CONCLUSION Complementary information obtained from fragmentation experiments of [M + H]+ (or [M + NH4]+ and [M-H](-) precursor ions is especially valuable for rapid identification of this kind of sesterterpenoid.

Lanostane-type C31 triterpenoid derivatives from the fruiting bodies of cultivated Fomitopsis palustris

Fifteen undescribed and five known lanostane-type C31 triterpenoid derivatives were isolated from the aqueous EtOH extract of the fruiting bodies of cultivated Fomitopsis palustris. Their structures were identified from the spectroscopic data and chemical degradation studies. The structures of palustrisoic acids A and H were confirmed by X-ray crystallography. Polyporenic acid B showed strong cytotoxicity against the HCT116, A549, and HepG2 cell lines with IC50 values of 8.4, 12.1, and 12.2 μM, respectively. Palustrisolides A, C, and G displayed weak cytotoxicity.