Heterogeneity of the interflavanyl bond in proanthocyanidins from natural sources lacking C-4 (C-ring) deoxy flavonoid nucleophiles.
The proanthocyanidin pool in the floral kingdom usually involves the presence of carbon-carbon bonds linking predominantly flavan-3-ol constituent moieties. Such an ensemble of flavan-3-ol units originates via electrophilic aromatic substitution of flavan-4-yl carbocations (or their equivalents) derived from flavan-4-ols and/or flavan-3,4-diols and the nucleophilic centers of the m-oxygenated A-rings of flavan-3-ol nucleophiles. In the absence of these potent flavan-3-ol nucleophiles with their aptitude for the formation of carbon-carbon bonds, alternative centers emerge as participants in interflavanyl bond formation. Such a phenomenon is demonstrated for the distribution of various profisetinidin-, prorobinetinidin-, proguibourtinidin-, promelacacinidin- and proteracacinidin-type pro- and leuco-anthocyanidins in several southern hemisphere heartwood species.
Ferreira
Daneel
D
Department of Pharmacognosy, School of Pharmacy, The University of Mississippi, University, MS 38677, USA. dferreir@olemiss.edu
Marais
Jannie P J
JP
Slade
Desmond
D
D002244:Carbon / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry; D015394:Molecular Structure; D044945:Proanthocyanidins / Q000737:chemistry*
D005419:Flavonoids; D044945:Proanthocyanidins; D002244:Carbon