Modulation of P-glycoprotein activity by acridones and coumarins from Citrus sinensis.

Bioguided fractionation of the roots of Citrus sinensis (Rutaceae) led to the isolation and identification of five coumarins, namely, clausarin, suberosin, poncitrin, xanthyletin and thamnosmonin, seven acridones, namely, acrimarine B, 2-methoxycitpressine I, citpressine I, buntanine, acrimarine E, honyumine and acrimarine C, and one terpenoid, namely, limonin. Among these compounds, clausarin, 2-methoxycitpressine I and acrimarine E inhibited P-glycoprotein-mediated drug efflux in K562/R7 human leukemic cells over-expressing P-glycoprotein.

HPLC-UV/PAD and HPLC-MS(n) analyses of leaf and root extracts of Vismia guineensis and isolation and identification of two new bianthrones.

In order to evaluate the possible use of the leaves instead of the roots of Vismia guineensis as a new source for the traditional use of this drug, the chemical composition of both organs were compared by HPLC-UV/PAD and HPLC-MS analyses. The leaves are analysed here for the first time. The results show the presence of five major classes of secondary metabolites having specific chromophores: anthraquinones, vismiones, flavonoids, xanthones and benzophenones. The molecular weights and characteristic fragments, compared with previous EI or HPLC-MS literature data, allowed the partial identification of the major peaks in the chromatograms. Six additional isomeric bianthrones and one anthraquinone were detected in the dichloromethane extract of the roots after long storage in solution; the targeted isolation of the bianthrones was performed and enabled the identification of two original C-geranyl derivatives. The chemical compositions of the extracts demonstrated that only a minority of the constituents is shared by both organs. Thus, in order to establish a definitive phytoequivalence, additional pharmacological investigations are required.

Antifungal chromans inhibiting the mitochondrial respiratory chain of pea seeds and new xanthones from Calophyllum caledonicum.

Two new xanthones, caledonixanthone M 1 and caloxanthone L 2, and one new acid, caledonic acid 6 were isolated from the hexane-soluble extract of the stem bark of Calophyllum caledonicum. In the course of this phytochemical study, seven other known compounds - calothwaitesixanthone, calozeyloxanthone, allanxanthone, isoapetalic acid 3, calolongic acid 4, apetalic acid 5 and isocalolongic acid 7 - were isolated. Their antifungal activity against the growth of the human pathogenic fungus Aspergillus fumigatus was then investigated. The results indicated that the crude extract, calolongic acid 4 and isocalolongic acid 7 exhibited strong inhibitory effects with MIC (80) values of 8, 4, 2 microg/mL, respectively. Besides, calolongic acid 4, its lactone derivative 4a and isocalolongic acid 7 markedly reduced the respiration of pea seed mitochondria.

Novel cytotoxic 4-phenylfuranocoumarins from Calophyllum dispar.

Eight new 4-phenylfuranocoumarins (1-8) have been isolated from the stem bark and the fruits of Calophyllum dispar, together with three known coumarins. The structures of 1-8 were established by means of spectroscopic analysis, including extensive 2D NMR studies. Some of these furanocoumarins exhibited significant cytotoxic activity against KB cells.