Antioxidant activities of carotenes and xanthophylls

Many studies have implicated ß-carotene as an antioxidant in vivo although there is little direct evidence to support this as yet. In contrast, there is considerable in vitro evidence for interaction of ß-carotene with free radicals, for its prop- erties as a chain-breaking antioxidant and in scavenging and quenching singlet oxygen. ß-Carotene has also been reported to protect against photosensitivity diseases in hu- mans. However, it offers little protection against metal- catalysed LDL oxidation ex vivo although the carote- noids within the LDL are consumed on oxidation with Cu2+, the sequence of activity being lycopene > ß-cryptoxanthin - > lutein/zeaxanthin > oc,ß-carotene, as deduced from rates of consumption during 1 h oxidation .