Dietary Supplement Antioxidant Carotenoid Source Naturals Astaxanthin is a natural compound found in the algae Haematococcus pluvialis. This powerful antioxidant has been found to be effective in protecting cell and mitochondrial membranes from oxidative stress. Recent studies have indicated that astaxanthin is more powerful than its carotenoid cousin, beta-carotene, at trapping singlet oxygen free radicals.