Cytokinins modulate a number of important developmental processes, including the last phase of leaf development, known as senescence, which is associated with chlorophyll breakdown, photosynthetic apparatus disintegration and oxidative damage. There is ample evidence that cytokinins can slow down all these senescence-accompanying changes. Here, we review relationships between the various mechanisms of action of these regulatory molecules. We highlight their connection to photosynthesis, the pivotal process that generates assimilates, however may also lead to oxidative damage. Thus, we also focus on cytokinin induction of protective responses against oxidative damage. Activation of antioxidative enzymes in senescing tissues is described as well as changes in the levels of naturally occurring antioxidative compounds, such as phenolic acids and flavonoids, in plant explants. The main goal of this review is to show how the biological activities of cytokinins may be related to their chemical structure. New links between molecular aspects of natural cytokinins and their synthetic derivatives with antisenescent properties are described. Structural motifs in cytokinin molecules that may explain why these molecules play such a significant regulatory role are outlined.
- MeSH
- antioxidancia chemie metabolismus MeSH
- cytokininy chemie metabolismus MeSH
- flavonoidy analýza MeSH
- fotosyntéza MeSH
- listy rostlin chemie růst a vývoj fyziologie MeSH
- molekulární struktura MeSH
- rostliny chemie MeSH
- vývoj rostlin MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Eleven 6-furfurylaminopurine (kinetin, Kin) derivatives were synthesized to obtain biologically active compounds. The prepared compounds were characterized using 1H NMR, mass spectrometry combined with HPLC purity determination and elemental C, H, N analyses. The biological activity of new derivatives was tested on plant cells and tissues in cytokinin bioassays, such as tobacco callus, detached wheat leaf chlorophyll retention bioassay and Amaranthus bioassay. The selected compounds were subsequently tested on normal human dermal fibroblasts (NHDF) and keratinocyte cell lines (HaCaT) to exclude possible phototoxic effects and, on the other hand, to reveal possible UVA and UVB photoprotective activity. The protective antioxidant activity of the prepared cytokinin derivatives was further studied and compared to previously prepared antisenescent compound 6-furfurylamino-9-(tetrahydrofuran-2-yl)purine (Kin-THF) using induced oxidative stress (OS) on nematode Caenorhabditis elegans damaged by 5-hydroxy-1,4-naphthoquinone (juglone), a generator of reactive oxygen species. The observed biological activity was interpreted in relation to the structure of the prepared derivatives. The most potent oxidative stress protection of all the prepared compounds was shown by 6-(thiophen-2-ylmethylamino)-9-(tetrahydrofuran-2-yl)purine (6) and 2-chloro-6-furfurylamino-9-(tetrahydrofuran-2-yl)purine (9) derivatives and the results were comparable to Kin-THF. Compounds 6 and 9 were able to significantly protect human skin cells against UV radiation in vitro. Both the derivatives 6 and 9 showed higher protective activity in comparison to previously known structurally similar compounds Kin and Kin-THF. The obtained results are surprising due to the fact that the prepared compounds showed to be inactive in the ORAC assay which proved that the compounds did not act as direct antioxidants as they were unable to directly scavenge oxygen radicals.
- MeSH
- cytokininy chemická syntéza chemie farmakologie MeSH
- kůže účinky léků MeSH
- lidé MeSH
- molekulární struktura MeSH
- ochranné látky chemická syntéza chemie farmakologie MeSH
- oxidační stres účinky léků MeSH
- ultrafialové záření * MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
Problematika pasivní bezpečnosti motocyklu a biomechaniky poranění motocyklisty se v posledních letech dostává do popředí zájmu a stává se postupně jedním z hlavních témat motocyklových výrobců. Snaha omezit závažné následky motocyklových dopravních nehod dvou víceméně nekompatibilních kolizních partnerů (motocykl – automobil) dnes vyúsťuje do evropských projektů, které mají za úkol zlepšit pasivní ochranu motocyklistů.
The problem of the passive safety of motorcycles and the biomechanics of the injuries of motorcyclists is recently gaining ground and is becoming one of the main themes of the motorcycle producers. The effort to limit the substantial consequences of the motorcycle traffic accidents of two more or less incompatible collision partners (motorcycle – car) leads to the current European projects having the task to improve the passive protection of motorcyclists.
