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Comparative phytochemical study of Caprifoliaceae

University of British Columbia

A comparative phytochemical study of the Caprifoliaceae was undertaken. No such study has ever been done. Extracts of fresh leaf material from 56 taxa collected throughout North America were examined for their content of phenolic compounds. Acid and base hydrolysis of the extracts yielded a large array of common phenolic acids and several unknowns. The unknowns occurred in small amounts and were not identified. The cyanogenetic glucoside, sambunigrin, was found to occur only in the genus Sambucus. Chlorogenic acid isomers were identified in the unhydrolyzed extracts of all plants examined. A chromatography system for the separation of these isomers is described. The dicaffeoylquinic acid isomers (isochlorogenic acid) occurred in all genera examined except; Sambucus which contained the monocaffeoylquinic acid isomers. Scopoletin, a 6 Me-7-OH-coumarin, was present in hydrolyzed extracts of Weigela. This is the only report of scopoletin in the Caprifoliaceae although other coumarins have been found in Diervilla and Symphoricarpos. A crystalline compound was isolated from extracts of the leaves of Viburnum davidii and was identified as 2 ' , 4, 4'-trihydroxy-dihydrochalcone. This is the first report of this compound being found, in plant material and also it is the first report of a dihydrochaleone with the 2',4’ dihydroxy structure rather than the 2',4',6' trihydroxy structure as found in phloretin. The flavonoids identified in this study yielded either the flavonols kaempferol or quercetin or the flavones apigenin or luteolin on hydrolysis. These four compounds displayed a wide variation of glycosylation and distribution throughout the taxa examined. The flavonols, which are considered to be the more primitive compounds, are found in Viburnum and Sambucus instead of the flavones. This would suggest that these genera are the most primitive of the family. The relatively more advanced flavones are more prominent in Symphoricarpos and Trlosteum thus suggesting that they are the more advanced genera of the family. The comparatively primitive compound amentoflavone (a biflavonyl) was found in Viburnum carlesii and V. X burkwoodii. The occurrence of sambunigrin in Sambucus only and the absence of the dicaffecylquinic esters in Sambucus support the idea that Sambucus is sufficiently different to be put into its own family, Sambucaceae (Hoch, 1892).

Text

2011-05-17

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http://hdl.handle.net/2429/34639

Botany

University of British Columbia

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