New unnatural gallotannins: Synthesis and biological activity evaluation using various in vitro assays

Absorption of solar light and processes of oxidation in living cells lead to biological changes on the cellular level. An overproduction and accumulation of reactive oxygen species (ROS) create an imbalance resulting in oxidative stress, which is responsible for a variety of degenerative diseases. The therapeutic potential of natural antioxidants is a source of inspiration for design of new biologically active compounds. Polyphenolic substances have gained a lot of importance because of their potential as prophylactic and therapeutic agents. Among various naturally occurring polyphenols, hydrolysable tannins represent a large group of strong antiradical and anticancer agents. The biological activities of natural and synthetic gallotannins range from beneficial antioxidants to damaging prooxidants and toxins. Due to their structural diversity and broad array of biological activities have great potential for the development of new pharmaceutically active compounds. Among various naturally occurring gallotannins, penta-1,2,3,4,6-O-galloyl-D-glucose (PGG) was the most widely studied. Presented research has been directed towards the synthesis of new PGG analogues derived from D-glucose, D-mannose, D-ribose and L-rhamnose. The aim of this study was to investigate the biological properties of structurally different gallotannins by various in vitro assays. The evaluation of the antioxidant, free radical scavenging capacity, bioprotective potential and their ability to induce or prevent DNA damage will be discussed in our contribution.