Nicolas Fabre

Determination of flavone, flavonol, and flavanone aglycones by negative ion liquid chromatography electrospray ion trap mass spectrometry

Eleven naturally occurring flavonoid aglycones, belonging to the representative flavone, flavonol, and flavanone types were separated by high performance liquid chromatography and analyzed on-line with negative ion electrospray ionization tandem mass spectrometry (ESI-MS/MS). In order to resolve the MS/MS spectra obtained, each compound was reinvestigated by direct loop injections using an ion trap mass spectrometer. The MSn spectra obtained allowed us to propose plausible schemes for their fragmentation supported by the analysis of five complementary synthetic flavonoid aglycones. The negative ion ESI-MS/MS behavior of the different aglycones investigated in this study revealed interesting differences when compared with the previously described patterns obtained using various ionization techniques in positive ion. Thus, concerning the retro Diels-Alder (RDA) fragmentation pathways, several structurally informative anions appeared highly specific of the negative ion mode. In addition, a new lactone-type structure, instead of a ketene, was proposed for a classic RDA diagnostic ion. We also observed unusual CO, CO2, and C3O2 losses which appear to be characteristic of the negative ion mode. All these results and these unusual neutral losses show that the negative ion mode was a powerful complementary tool of the positive ion mode for the structural characterization of flavonoid aglycones by ESI-MS/MS.

Two tetrahydroquinoline alkaloids from Galipea officinalis

Abstract Two tetrahydroquinoline alkaloids have been isolated from the bark of Galipea officinalis Hancock. Their structures have been established by spectroscopic methods. The compounds were named angustureine (1,2,3,4-tetrahydro-2(n-pentyl)-1-methylquinoline) and galipeine (2-[(3′-hydroxy-4′-methoxy-phenylethyl)]-2,3,4-tetrahydro-1-methylquinoline).

Novel indole-type glucosinolates from woad (Isatis tinctoria L.)

Abstract Four novel indole-type glucosinolates ( 1 – 1 ′ and 2 – 2 ′ ), together with six other known glucosinolates, were isolated from the seeds of Isatis tinctoria L. and their structures elucidated by spectroscopic analysis. Combining an aliphatic and an indole moiety, they represent an original family of glucosinolates, thus broadening the structural diversity of those plant metabolites.

Direct characterization of isoquinoline alkaloids in a crude plant extract by ion-pair liquid chromatography–electrospray ionization tandem mass spectrometry: example of Eschscholtzia californica

An ion-pair HPLC-ESI-MS-MS method has been developed for the direct and rapid characterization of isoquinoline alkaloids in a crudely purified extract of the aerial parts of Eschscholtzia californica (Papaveraceae). This plant was chosen because of its increasing use in pharmaceutical industries and because its well known alkaloid composition allows the optimization of the experimental procedure through an on-line analytical sequence. Thus, 14 isoquinoline alkaloids of different types were detected and characterized. The identities of these compounds were confirmed unambigously by their fragmentation and UV spectra obtained by LC-diode-array detection. Various experiments including tandem mass spectrometry and in-orifice collision induced dissociation were performed and prove that MS-MS is a very efficient technique to identify these compounds. An explanation for each isoquinoline alkaloid type MS-MS fragmentation pattern is proposed and indicates similar neutral and/or radical losses. The order of the fragmentation depended on the type of compound but the lost fragments were similar.

Cytotoxic and antiplasmodial xanthones from Pentadesma butyracea.

Four new xanthones, butyraxanthones A-D (1-4), were isolated from the stem bark of Pentadesma butyracea, together with six known xanthones (5-10) and a triterpenoid (lupeol). The structures of 1-4 were established by spectroscopic methods. Compounds 1-10 were tested in vitro for antiplasmodial activity against a Plasmodium falciparum chloroquine-resistant strain and for cytotoxicity against a human breast cancer cell line (MCF-7). Nearly all of these xanthones exhibited good antiplasmodial activity, and some of them also demonstrated potent cytotoxicity.

Hammada scoparia flavonoids and rutin kill adherent and chemoresistant leukemic cells

In search for compounds able to reduce cell adhesion-mediated drug resistance (CAM-DR), we studied effects of Hammada scoparia extracts on leukemic cells adherent or in suspension. We show that H. scoparia flavonoidic fraction and its compound rutin induce apoptosis specifically in adherent leukemic cells and abolish CAM-DR. Importantly, rutin inhibited survival of adherent leukemic progenitors (CD34(+)38(-)123(+)) but spared normal progenitors (CD34(+)38(-)). The pro-apoptotic effects of rutin were correlated with a decrease of active GSK3β and inhibitors of GSK3β reproduced rutin-induced cytotoxicity. This study uncovers the potential of H. scoparia flavonoids and rutin to overcome CAM-DR in acute myeloid leukemia.

Analysis of minor flavonoids in Piper hostmannianum var. berbicense using liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry.

The fragmentations of hydroxylated flavanones, chalcones and dihydrochalcones were investigated by direct loop injection using an ion trap mass spectrometry equipped with atmospheric pressure chemical ionization (APCI) probe. Some of them have been isolated from the leaves of Piper hostmannianum var. berbicense and standards were used to confirm their fragmentation behaviour. In negative ion mode, fragmentations of these three types of flavonoids revealed specific diagnostic ions which allowed us to identify aglycones in a crude plant extract. The major fragment ion obtained in MS/MS experiment for methoxylated chalcones is the neutral loss of a methyl radical whereas a H(2)O molecule is lost in the case of methoxylated dihydrochalcones. Methoxylated chalcones and flavanones isomers could be differentiated by the relative intensity ratio of [M-H-CH(3)]*(-) and [M-H-C(2)H(2)O](-) ions. Based on UV and MS data, a decision tree that includes UV lambda(max) absorptions and MS/MS diagnostic ions was built in order to obtain structural information of unknown compounds present in the extract. This tree was used to identify flavonoids in the ethyl acetate extract of P. hostmannianum var. berbicense leaves after analysis by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization ion trap multistage mass spectrometry. A total of 11 flavonoids were tentatively characterized based on the MS fragmentations pattern observed in MS(n) experiments.

An antioxidant sinapic acid ester isolated from Iberis amara

The isolation of 6-O-sinapoyl sucrose (1) from Iberis amara seeds and an evaluation of its antioxidative properties in comparison with sinapic acid and ascorbic acid are reported.

A review of traditional remedies of ciguatera fish poisoning in the Pacific.

Ciguatera fish poisoning (CFP) is an illness caused by eating tropical coral fish contaminated with ciguatoxins (CTXs). The clinical management of patients with CFP is generally supportive and symptomatic in nature as no antidote exists. Of the many drugs prescribed, several have been claimed to be efficient in small, uncontrolled studies, but the outcomes of treatments with these medicines are often contradictory. In New Caledonia, traditional remedies are commonly employed in the treatment of CFP and of the 90 plant species catalogued as useful in CFP, the most popular herbal remedy by far is a decoction prepared from the leaves of Heliotropium foertherianum Diane & Hilger (Boraginaceae). Other important plants used in the treatment of CFP include Euphorbia hirta L. (Euphorbiaceae) and Vitex L. sp. (Lamiaceae). This review focuses on the evidence for efficacy of these species and pharmacological studies which support their use. Other plants used in CFP and the conventional treatment of CFP are also discussed briefly. Copyright

Iridoid keto-glycosides from Caryopteris × Clandonensis

Abstract Two new iridoid keto-glycosides, clandonoside and 8- O -acetylclandonoside, together with their hydrates, were isolated from the stems of Caryopteris × Clandonensis besides the known harpagide and 8- O -acetylharpagide. The structure of clandonoside and 8- O -acetylclandonoside were established as harpagide-aglucone-1- O -β- d -ribohexo-3-ulopyranoside and 8- O -acetylharpagide-aglucone-1- O -β- d -ribohexo-3-ulopyranoside, respectively, by spectroscopic methods. This is the first report of a C-1 linked β- d -ribohexo-3-ulopyranose (β- d -ketohexose) iridoid.