Bioactive carotenoids: potent antioxidants and regulators of gene expression.

Carotenoids are plant pigments, some of which act as a vital source of vitamin A to all animals, that appear to have additional benefits to primates. They are potent antioxidants and photoprotectants and can additionally modulate gene activity resulting in protection from experimentally-induced inflammatory damage and neoplastic transformation. Anti-neoplastic properties appear tightly correlated to their ability to induce the gap junctional protein connexin 43 (Cx43). This when upregulated leads to decreased proliferation and decreased indices of neoplasia in animal and human cells. Delivery of natural carotenoids can be compromised by poor bioavailability. To overcome this, a synthetic water-dispersible derivative of astaxanthin has been synthesized and shown to be: highly bioavailable; a potent antioxidant; protective against experimental ischemia-reperfusion injury and capable of inducing Cx43, suggesting antineoplastic potential. The ability to deliver biologically active carotenoids at high concentration and with good reproducibility appears to have been achieved.