Effect of polymeric caffeic acid on antitumour activity and natural killer cell activity in mice

The antitumour activity and immunomodulating activity of synthesized lignin-like polyphenols in mice were determined. Polymerized polyphenols were prepared using caffeic acid as the precursor. The intake of both polymeric and monomeric caffeic acid inhibited the growth of B7-P815 tumours in mice, but we found that only the monomers inhibited tumour growth in vitro. Oral administration of polymerized caffeic acid, but not monomeric caffeic acid, substantially increased interferon-γ production in splenocytes stimulated with phorbol 12-myristate 13-acetate and ionomycin. Moreover, natural killer activity was markedly upregulated in mice that were administered polymerized caffeic acid compared with mice administered water or caffeic acid monomers. Lastly, we determined that caffeic acid monomers were absorbed more easily than polymers, but ingested polymers were less susceptible to degradation into monomers by digesting enzymes. Taken together, our results suggest that polymerized caffeic acid administered orally can upregulate systemic immunity and inhibit tumour cell growth.