The major cytotoxic activity of crude extracts of Nectandra rigida Nees is due to dehydrodiisoeugenol,the sample isolated being slightly enriched in the dextrorotatory enantiomer. Galgravin and two new tetrahydrofuranoid lignans, nectandrin A and nectandrin B, were also isolated and characterized along with small quantities of vanillin, 2,6-dimethoxybenzoquinone, and the known lauraceous alkaloid laurelliptine. The neolignans are of potential chemotaxonomic significance in the study of the Lauraceae.
The flowers of the Mexican tree Quararibea funebris (Llave) Vischer (Bombacaceae) have been shown to give rise to the enolic 7-lactone 1, its amino analogue 3, the saturated lactone 4, and the parent amino acid (2S,3S,4R)-7-hydroxyisoleucine (5), as well as the novel pyrrole alkaloid funebrine (6). The structure determination of funebrine by X-ray crystallography is discussed and a hypothesis for its biogenesis offered.
Extracts of the stem parts of the woody Composite Eremanthus elaeganus yielded lupeol acetate (1 ), friedelin (Z), epifriedelinol (3). a mixture of sitosterols, the flavonoids tamarixetin (3,5,7,3'-tetrahydroxy-4'-methoxyflavone), genkwanin (5,4'-dihydroxy-7-methoxyflavone),and luteolin 7-methyl ether (5,3',4'-trihydroxy-7-methoxyflavone), and the three novel modified germacranolides eremantholide A ( 5 ) . B (6), and C (minor component) ( 7 ) . The structures of eremantholides A and B were determined by X-ray crystallography, and a crystallographic comparison between the two structures is given. Eremantholide A reacts with propane-I -thiol by a novel 1.6-Michael-type addition which may simulate the mode of its cytotoxic action.
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