Astaxanthin is the most powerful antioxidant and anti-inflammatory known to science until this moment. Put simply, antioxidants are molecules which hampers the oxidation ( break down) of the cells. They are doing this by neutralizing free radicals, and hence provide protection against the damaging effect of these free radicals, which if not balanced leads to oxidation of the cells.
The richest source of natural astaxanthin in nature is Haematococcus pluvialis, a microalgae and natural carotenoid that can be found in artic marine environment and common freshwater rock pools across the world.