Protective effects of foods rich in carotenoids against DNA damages due to reactions of chemically induced triplet states of melanin derivatives

• Applicants: Professor Dr. Volker Böhm; Professor Dr. Wilhelm Stahl
• Subject Area: Food Chemistry
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 349764062

Carotenoids comprise a group of secondary plant constituents in our diet with photoprotective properties. Human intervention studies have proven the light-protective effects of the major carotenoids beta-carotene, lycopene and lutein. After ingestion, the compounds are absorbed and distributed via the blood stream to the target tissues (skin and eye) where they reveal preventive effects. These effects are mechanistically linked to their antioxidant properties such as quenching of light-induced excited triplet state molecules or singlet oxygen and scavenging of reactive oxygen species including superoxide or lipid peroxides, thus contributing to the prevention of photooxidative DNA damage. Upon UV-irradiation, DNA is oxidized and cyclobutane pyrimidine dimers (CPDs) are generated in light-dependent reactions. On a time scale, these processes occur directly after light-exposure. Recently, it has been shown that in addition to these direct effects, a so called dark reaction is initiated in which a time delayed (hours) formation of CPDs (dark CPDs) occurs. In a UV-induced reaction sequence, degradation products of melanin and reactive oxygen species form dioxetanes, which decompose to yield excited triplet carbonyls. Upon quenching of the excited triplet state, dark CPDs are formed. The pattern of the CPDs depends on their way of formation, and its analyses by means of HPLC-MS/MS allows to distinguish between directly and delayed formed species. Carotenoids are efficient quenchers of excited triplet carbonyls and thus should inhibit the generation of dark CPDs. In model systems and cell culture (melanocytes, skin model) carotenoids from dietary sources (carrots, tomatoes, squash) will be used to investigate their effects on the formation of dark CPDs. Key aspect is a nutritional approach to address the properties of complex food systems inhibiting biologically defined damages following UV exposure and attributing photoprotective effects to the key components and a major mechanism, namely quenching of excited triplet states.

• DFG Programme: Research Grants