Labdane and pimarane diterpenes from Croton joufra.

From the chloroform extract of the leaves of Croton joufra, the diterpenes 2alpha,3alpha-dihydroxy-labda-8(17),12(13),14(15)-triene and 3beta-hydroxy-19-O-acetyl-pimara-8(9),15-dien-7-one, were isolated. Their structures were established by spectroscopic methods. One of the compounds showed weak lethality in the brine shrimp assay.

Cytotoxic natural products from thai plants: a recent study.

Natural products will continue to be the most prolific source of bioactive compounds. Natural products exhibiting antitumor activity continue to be the subject of extensive research aimed at the development of drugs for the treatment of different human tumors. It is generally accepted that natural products offer a diversity and complexity of structure unmatched by even the most active imaginations of synthetic organic chemists. This paper reviews the research of selected Thai plants for the discovery of therapeutic agents. Attention will be focused on our recent research on Thai plants that possess cytotoxic properties. Synthetic modification and reaction of some of these compounds aimed at enhancing their potency will also be presented.

Chemical investigation of mammea siamensis.

A new 4-alkylcoumarin, mammea B/AC cyclo D ( 1 ), together with a 4-phenylcoumarin, mammea A/AC cyclo D ( 2 ), were isolated from the hexane extract of the dried flower of Mammea siamensis . Their structures were determined on the basis of spectroscopic evidence.

NMR study of seven coumarins from mammea siamensis.

Seven known mammea coumarins, mammea A/AA cyclo D ( 1 ), mammea A/AD cyclo D ( 2 ), mammea A/AB cyclo D ( 3 ), mammea A/AC cyclo F ( 4 ), mam-mea A/AB cyclo F ( 5 ), mammea A/AA cyclo F ( 6 ), mammea B/AC cyclo F ( 7 ), were isolated for the first time from the hexane extract of Mammea siamensis . A detailed analysis of both 1D and 2D NMR spectral data of these compounds was made.

Reinvestigation of derris reticulata.

The novel compound 1'''-hydroxy-2''',3'''-epoxylupinifolin ( 1 ), together with three known prenylated flavanones were identified from the stem of Derris reticulata during our reinvestigation of the plant. The structures were determined by spectroscopic methods including detailed study of NMR spectral data (DEPT, 2D-COSY, HMQC and HMBC) as well as by chemical derivatizations.

Cyanogenic and non-cyanogenic glycosides from Manihot esculenta.

In addition to lotaustralin and linamarin, a novel cyanogenic glycoside, 2-((6-O-(beta-D-apiofuranosyl)-beta-D-glucopyranosyl)oxy)-2-met hylbutanenitrile , two novel non-cyanogenic glycosides, (2S)-((6-O-(beta-D-apiofuranosyl)-beta-D- glucopyranosyl)oxy)butane and 2-((6-O-(beta-D-apiofuranosyl)-beta-D-glucopyranosyl)oxy)propane, and a simple non-cyanogenic glycoside, ethyl beta-D-glucopyranoside, were isolated from an ethanolic extract of the fresh root cortex of Manihot esculenta. From a methanolic extract of the fresh leaves of this species lotaustralin and linamarin, and two flavonoid glycosides, kaempferol-3-O-rutinoside and quercetin-3-O-rutinoside were isolated.

1H- and 13C-nmr assignments of phyllanthin and hypophyllanthin: lignans that enhance cytotoxic responses with cultured multidrug-resistant cells.

Complete 1H-nmr data and unambiguous assignments of the 13C-nmr spectra of phyllanthin [1] and hypophyllanthin [2] were obtained through extensive nmr studies, including homonuclear COSY, homonuclear decoupling, APT, HETCOR, nOe difference, selective INEPT, and COLOC experiments. The absolute configuration of hypophyllanthin [2] was determined by cd. Neither of these lignans demonstrated significant cytotoxic activity when evaluated with a battery of cultured mammalian cells, but both were found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB cells. In addition, 1 was found to displace the binding of vinblastine with membrane vesicles derived from this cell line, suggesting an interaction with the P-glycoprotein.

Naturally occurring cyclohexene epoxides revisited.

Cyclohexene epoxides are a small group of naturally occurring oxygenated cyclohexanes, most of which have been found in plants of the Uvaria genus. Some of these molecules possess pharmacological activity and have been isolated from plants that have been used in traditional medicine in Thailand. The biogenesis of these compounds was thought to have been fully explained when all the intermediates of a proposed synthetic pathway had been isolated from a single Uvaria species. Further studies on naturally occurring cyclohexene epoxides identified novel compounds, whose presence could not be explained by the accepted scheme. An alternative biosynthetic pathway that was formerly considered unfavourably appears to fit currently available evidence.