Oligomeric proanthocyanidins

Roux has commented that condensed tannins (and proanthocyanidins) have not attracted study because the weight of the research effort is invariably dispropor- 

---

Recent scientific investigations of natural polyphenols have demonstrated their powerful antioxidant property (Niki et al, 1995). Several classes of polyphenols have been chemically identified. Some of these are grape polyphenols, tea polyphenols, soy polyphenols, oligomeric proanthocyanidines (OPA) and other natural polyphenols of the flavone class. Rice bran polyphenols are different from the above in that they are p-hydroxy cinnamic acid derivatives such as p-coumaric acid, ferulic acid and p-sinapic acid. Tricin, a flavone derivative, has also been isolated from rice bran. 

Waterhouse et al., A comparison of methods for quantifying oligomeric proanthocyanidins from grape. Am. J. Enol. Vitic., 51, 383, 2000. 

Recently published literature described either the improvement of the strategies devoted to the synthesis of either catechins derivatives or oligomeric proanthocyanidins or the use of a synthetic program as a way to obtain... 

Investigations of the conformational properties of the flavan-3-ols and oligomeric proanthocyanidins have hitherto involved a variety of molecular mechanics and molecular orbital computations in combination with crystal structures, time-resolved fluorescence, as well as and NMR methods. Representative references to all these techniques may be found in the papers listed in Refs. 241-247, 250. These NMR papers incidentally also represent the major contributions regarding the conformation of proanthocyanidins, and may be summarized in a conformational context by reference to the significant contributions of Hatano and Hemingway. 

Eerreira, D. and Slade, D., Oligomeric proanthocyanidins naturally occurring 0-heterocycles,... 

Kuliev, Z.A. et al., Oligomeric proanthocyanidin glycosides of Clementsia semenovii and their biological activity. Ill, Chem. Nat. Compd., 36, 60, 2000. 

Balde, A.M. et al., Oligomeric proanthocyanidins possessing a doubly linked structure from Pavetta owariensis. Phytochemistry, 38, 719, 1995. 

Fine AM. 2000. Oligomeric proanthocyanidin complexes history, structure, and phytopharmaceutical applications. Altem Med Rev 5 144-151. 

Proanthocyanidins is a class of flavonoids. Proanthocyanidins are derived from the flavonoids oligomeric proanthocyanidins (OPCs) and therefore proanthocyanidins have been formerly called condensed tannins. Moreover, all proanthocyanidins have similar structures and the only differences are slight changes in the shape and attachments of the polyphenol rings. The diverse proanthocyanidins could always be found together, ranging from a proanthocyanidin unit to complex molecules with many linked units as the oligomers in nature. 

Oligomeric proanthocyanidin Widespread (fruit, vegetables, nuts, COX, LOX [Al, antioxidant]... 

Phytochemical Content high in carotenoids (beta-carotene), polyphenols (anthocyanins, oligomeric proanthocyanidins, tannins, luteolin, quercetin, apigenin)... 

Roles of Polyphenols, Flavonoids, and Oligomeric Proanthocyanidins in Cancer Chemoprevention... 

---