Swietemicrolides A-D, mexicanolide-type limonoids from the bark of Swietenia macrophylla with in vitro cytotoxic and α-glucosidase inhibitory activities.

Four new mexicanolide-type limonoids, swietemicrolides A-D (1-4), together with three known compounds (5-7) were isolated from an ethyl acetate extract of the bark of Swietenia microphylla. 1 and 2 had 1,8-hemiacetal systems whilst 3 and 4 shared hexacyclic skeletons consisting of three fused five-membered rings. The structures of the isolated compounds were determined using spectroscopic methods. The five limonoids (1-5) were tested in vitro for their cytotoxic effects against two human cancer cell lines (KB carcinoma and A549 lung cancer cells) and α-glucosidase inhibitory activity. None of them showed significant cytotoxic activity, however, swietemicrolide C (3) exhibited strong effect towards α-glucosidase. Moreover, a possible biosynthetic pathway for compounds 1-4 was proposed to support a comprehensive understanding of the configurations of the new limonoids.

Cytotoxic Coumarins from the Bark of Mammea siamensis.

A new geranylated coumarin, (E)-4-(1-hydroxypropyl)-5,7-dihydroxy-6-(3,7-dimethyl-2,6-octadienyl)-8-(3-methyl-1-oxobutyl)coumarin (named surangin D), was isolated from the bark of Mammea siamensis collected in Vietnam, along with four known coumarins, surangins B and C, and theraphins B and C, and seven xanthones, 1,7-dihydroxyxanthone, 7-hydroxy-1-methoxyxanthone, 1,7-dimethoxyxanthone, 1,7-dimethoxy-6-hydroxyxanthone, 1,6,7-trihydroxyxanthone, 1,3,7-trihydroxyxanthone, and 1,7-dihydroxy-3-methoxyxanthone. Their structures were determined by spectroscopic methods (mainly 1D- and 2D-NMR) and preparation of methylated derivatives. The four coumarins, surangins C and D and theraphins B and C, were tested for inhibition of cell proliferation in DLD-1 (colon cancer), MCF-7 (breast adenocarcinoma), HeLa (human cervical cancer) and NCI-H460 (human lung cancer) cell lines using the sulforhodamine B (SRB) assay. In all four cell lines, theraphin C showed the strongest activity (IC50 in the range of 1.6-5.7 µM). Testing the anti-proliferative effect of the methylated derivatives showed reduced cellular effects of all derivatives, indicating that the number and position of free hydroxyl groups were very important for the anti-proliferative effect.

Isoprenylated xanthone and benzophenone constituents of the pericarp of Garcinia planchonii.

A new xanthone, planchoxanthone (1), together with six known compounds, garcinianone A (2), cowanin (3), rubraxanthone (4), f-mangostin (5), dulcisxanthone B (6), and guttiferone Q (7), were isolated from an n-hexane extract of the pericap of Garcinia planchonii. Their structures were elucidated using spectroscopic methods. Antioxidant activity of the isolated compounds was tested using the DPPH free radical scavenging assay.

A new xanthone from the bark of Calophyllum thorelii.

A new xanthone, calothorexanthone, together with five known compounds, garbogiol, 1,4,8-trihydroxyxanthone, δ-tocotrienol, 1,7-dihydroxyxanthone and globuxanthone, was isolated from a petroleum ether extract of the bark of Calophyllum thorelii. Their structures were established on the basis of spectroscopic methods, mainly one- and two-dimensional NMR. Antioxidant activity of the isolated compounds was tested using DPPH free radical scavenging assay and some exhibited remarkable effects with IC50 of 13.63-17.46 µg mL(-1).

Cytotoxic geranylated xanthones and O-alkylated derivatives of alpha-mangostin.

Two new geranylated xanthones, 6-O-methylcowanin (4) and oliverixanthone (5), along with five known compounds, cowanin, rubraxanthone, cowaxanthone, cowanol, and beta-mangostin, have been isolated from the bark of Garcinia oliveri. For comparison of their biological activities, one mono- and seven di-O-alkylated alpha-mangostin derivatives were synthesized from alpha-mangostin. The structures of all compounds were assigned by spectroscopic methods (1D and 2D NMR and MS). Cytotoxicity of selected xanthones against MCF-7 and DLD-1 cell lines was examined. Evaluation of the structure-activity relationship showed that alpha-mangostin had the strongest activity, and all the O-alkylated alpha-mangostin derivatives showed reduced activity compared to the naturally occurring alpha-mangostin.