Preparative separation and bioactivity of oligomeric proanthocyanidins

Oligomeric proanthocyanidins are among the most widely distributed polyphenols in the plant kingdom, being endowed with antioxidant, anti-inflammatory, antimicrobial, immunomodulatory, antitumor and cardioprotective activities. Since oligomeric proanthocyanidins are found in limited amounts in plants and plant-derived products, there is a great need for efficient separation methodologies that can supply analytical quality standards or sufficient material for further bioassays. By efficiently providing a good molar mass distribution of oligomeric proanthocyanidins according to their degree of polymerization, Sephadex LH is the most used sorbent in column chromatography, together with other size exclusion polymers, such as Toyopearl, Diaion, MCI gel CHP or Amberlite. Combination of normal and reversed-phase high pressure liquid chromatography can significantly reduce the total number of chromatographic steps required to obtain high purity oligomeric proanthocyanidins, whereas hydrophilic interaction liquid chromatography on Diol phases can yield proanthocyanidins with a higher degree of polymerization. By lacking a solid support, countercurrent separations can solve issues related to irreversible adsorption, giving higher recoveries, low sample denaturation and a facile scale-up from analytical to industrial production. By taking advantage of the complementarity of all these chromatographic techniques, high-purity oligomeric proanthocyanidin fractions or individual compounds can be obtained on a large scale in a reduced number of separation steps.