-
[show abstract]
[hide abstract]
ABSTRACT: Limonoids, a class of tetranortriterpenoids, exhibit various biological effects, such as insect antifeedant and growth regulating activities, antimicrobial activity, potent cell adhesion inhibitory effects, antimalarial activity, anticancer activities, and antioxidant activity. The potential application brings the need for reliable, fast and low-cost analysis of this class of compounds.
Six cipadesin limonoids (1-6), including a pairs of isomers, from leaves and barks of Cipadessa cinerascens were investigated by electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in positive-ion mode. Characteristic processes were further studied by theoretical calculations.
1,3-Hydrogen rearrangement might play a significant role in the cleavage of -O- bridge bond in ring B and further produces some characteristic ions. For [M + Na](+) precursor ions, the product ion at m/z 133 might indicate the structure of ring A and the losses of CO(2) and AcOH occur readily. Interestingly, the radical product ion at m/z 460 from [M + Na](+) ions seems to be the characteristic ion for compound 1. A deuterium-labeling experiment supported the processes forming the radical ion. For [M + NH(4)](+) ions, high-abundance product ions resulting from sequential loss of AcOH can be observed. In addition, a pairs of isomers was unambiguously differentiated based on MS or MS/MS spectra.
In summary, sufficient information obtained from fragmentation experiments of [M + Na](+), [M + NH(4)](+) or [M + H](+) precursor ions is especially valuable for rapid identification of these limonoids or their metabolites in complex mixtures. The high-abundance radical product ion is of scientific interest.
Rapid Communications in Mass Spectrometry 03/2012; 26(5):563-71. · 2.79 Impact Factor
-
Rapid Communications in Mass Spectrometry 03/2010; 24(8):1211-5. · 2.79 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
To obtain sufficient information for rapid structural elucidation of this class of compounds using MS.
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.
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.
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.
Phytochemical Analysis 03/2010; 21(4):374-83. · 2.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In the title compound, C(16)H(24)NO(+)·Br(-)·C(20)H(14)O(2), the N-hetero-cyclic six-membered ring assumes a half-chair conformation. The two naphthalene ring systems are nearly perpendicular to one another, making a dihedral angle of 89.5 (2)°. Inter-molecular O-H⋯Br hydrogen bonding helps to stabilize the crystal structure.
Acta Crystallographica Section E Structure Reports Online 01/2010; 66(Pt 4):o768. · 0.35 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: THE TITLE COMPOUND [SYSTEMATIC NAME: (3bS,5aS,7R,8R,10aR,10bS)-7-meth-oxy-10b-methyl-3b,4,5,6,7,8,9,10,10a,10b,11,12-dodeca-hydro-5a,8-methano-5aH-cyclo-hepta-l[5,6]naph-tho[2,1-b]furan-7-methanol], C(21)H(30)O(3), was isolated from the beans of Coffea robusta. The mol-ecule contains five fused rings including a furan ring. The two six-membered rings are in chair conformations, but the third six-membered ring and the five-membered aliphatic ring adopt envelope conformations. Inter-molecular O-H⋯O hydrogen bonding is present in the crystal structure.
Acta Crystallographica Section E Structure Reports Online 01/2010; 66(Pt 4):o760. · 0.35 Impact Factor
-
Rapid Communications in Mass Spectrometry 11/2009; 23(23):3881-5. · 2.79 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Brevianamide J (1), a new indole alkaloid dimer, was isolated together with four new diketopiperazine alkaloids (brevianamide K-N, 2-5) from the solid-state fermented culture of Aspergillus versicolor. Their structures were elucidated on the basis of spectral data. X-ray crystallographic analysis confirmed the structures of 1 and 4.
Organic Letters 08/2009; 11(16):3714-7. · 5.86 Impact Factor
-
Helvetica Chimica Acta 04/2009; 92(4):677 - 688. · 1.48 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Two diastereoisomeric decalins, (2S,4aS,5S,6R)- and (2S,4aS,5R,6R)-5-(2-hydroxyethyl)-1,1,4a,6-tetramethyldecalin-2,6-diol (5 and 6) were prepared from the degradation products of oleanolic acid. Starting from 6, (−)-ambrox (4) was synthesized.
Helvetica Chimica Acta 04/2008; 91(4):734 - 740. · 1.48 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Two new diterpenes and ent-15alpha-hydroxykaur-16-en-19-oic acid 11,12-acetonide (3), together with 23 known compounds were isolated from the dried aerial parts of Nouelia insignis Franch. The structures of new compounds were determined to be ent-14beta,15alpha-dihydroxykaur-16-en-19-oic acid (1), ent-14beta-hydroxy-15-oxokaur-16-en-19-oic acid (2) on the basis of spectral and chemical evidence. The structure of ent-11alpha,16alpha-epoxy-15alpha-hydroxy-16S-kaur-19-oic acid (4) was confirmed by X-ray crystallographic analysis.
Journal of Asian Natural Products Research 10(1-2):125-31. · 0.94 Impact Factor
