Structural features and bioavailability of four flavonoids and their implications for lifespan-extending and antioxidant actions in C. elegans

Various studies have demonstrated longevity effects of flavonoids, a major sub-group of plant polyphenolic compounds, in Caenorhabditis elegans. To better understand their structure-activity relationship in vivo we have used a comparative approach by exposing C. elegans to the structurally related flavonoids myricetin, quercetin, kaempferol and naringenin, and assessed their impact on lifespan and on putative modes of action. The bioavailability of the tested flavonoids was demonstrated by high-performance liquid chromatography with diode-array detection (HPLC/DAD) and a 2-aminoethyl diphenyl borate-based in vivo approach. While all flavonols increased lifespan in wild-type, only myricetin elongated the mev-1(kn1) lifespan, suggesting that the flavonols antioxidant action alone is not sufficient for longevity. Structural prerequisites of high antioxidant action in vitro were also essential to reduce the reactive oxygen species (ROS) load in vivo in C. elegans and were tested in isolated mouse muscle mitochondria. Since the insulin/IGF-like signaling (IIS) cascade is a key regulator of lifespan, all compounds were tested for the ability to cause nuclear translocation of the FOXO transcription factor DAF-16 and changes in target gene expression. An increased DAF-16 translocation and sod-3 promoter activity were observed with all flavonoids but was independent of their ROS scavenging capability and their effects on lifespan.