7-Phenylethynylimidazo[4,5-b]pyridine and its riboside have been newly developed as fluorescent carbon-substituted cytokinin analogues. Palladium-catalyzed coupling of 7-iodo-3-(tri-O-acetyl-beta-D-ribofuranosyl)imidazo[4,5-b]pyridine with phenylacetylene followed by ammonolysis afforded the 7-phenylethynyl riboside via its tri-O-acetate. Acid hydrolysis of the riboside provided its free base, which showed a marked enhancement in fluorescence intensity in an aqueous alkaline solution. The free base and its riboside were more active than the corresponding 6-phenylethynylpurine and its riboside, respectively, in Amaranthus betacyanin and tobacco callus bioassays. Surprisingly, the imidazo[4,5-b]pyridine base exhibited strong cytokinin activity comparable to that of N(6)-benzyladenine in the tobacco callus bioassay. This compound would be useful for studying localization and transport of cytokinins in cells or tissues of plants.
BACKGROUND Chronic exposure to ultraviolet (UV) radiation promotes skin photoaging, which is clinically characterized by dryness, laxity, and wrinkling. Sea cucumber (Stichopus japonicus) (SC) is a marine organism with culinary and medicinal applications, especially in Asian countries. It is also a potential nutraceutical as it exhibits bioactive effects, such as antioxidant, antitumor, and anticancer activity. This study examined the effects of SC and its hydrolysate (SCH) on ultraviolet A (UVA) induced skin barrier function and wrinkle formation using hairless mice. RESULTS Ultraviolet A significantly induced transepidermal water loss and wrinkle formation, which were significantly mitigated upon oral administration of SC and SCH. Sea cucumber also mitigated the UVA‐induced downregulation of epidermal natural moisturizing factors and the upregulation of Aqp3, Mmp13, Tnfa, and Il6 mRNA levels in the mouse skin. CONCLUSION Taken together, these results suggest that dietary SC and SCH exert anti‐photoaging effects by modulating filaggrin synthesis and desquamation in the epidermis and regulating the NF‐κB pathway in the skin. Our research indicates that SC and SCH have potential applications in nutricosmetics for photoaging. © 2021 Society of Chemical Industry.
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