Ubiquinone (coenzyme Q10, Q10) represents an endogenously synthesized lipid‐soluble antioxidant which is crucial for cellular energy production but is diminished with age and under the influence of external stress factors in human skin. Here, it is shown that topical Q10 treatment is beneficial with regard to effective Q10 replenishment, augmentation of cellular energy metabolism, and antioxidant effects. Application of Q10‐containing formulas significantly increased the levels of this quinone on the skin surface. In the deeper layers of the epidermis the ubiquinone level was significantly augmented indicating effective supplementation. Concurrent elevation of ubiquinol levels suggested metabolic transformation of ubiquinone resulting from increased energy metabolism. Incubation of cultured human keratinocytes with Q10 concentrations equivalent to treated skin showed a significant augmentation of energy metabolism. Moreover, the results demonstrated that stressed skin benefits from the topical Q10 treatment by reduction of free radicals and an increase in antioxidant capacity. © 2015 BioFactors, 41(6):383–390, 2015

The newly synthesized 2-(alk-3-en-1-ynyl)cyclohex-2-enones 4 undergo photodimerization (chemoand regio-)selectively at the exocyclic C¼C bond to give diastereoisomeric mixtures of 1,2-dialkynyl-1,2-dimethylcyclobutanes. On irradiation of 4 in the presence of 2-chloroacrylonitrile, cyclobutane formation occurs again (chemo-and regio-)selectively at the exocyclic C¼C bond to afford diastereoisomeric mixtures of 2-alkynyl-1-chloro-2-methylcyclobutanecarbonitriles. Similarly, compounds 4 undergo photoaddition to 2,3-dimethylbuta-1,3-diene exclusively at the exocyclic C¼C bond to afford mixtures of [2 þ 2] and [4 þ 2] cycloadducts.1. Introduction. -Quite recently, we have reported [1] that the (photo)reactivity of 3-alkynylcyclohex-2-enones was completely altered by extending the conjugation of the side chain at C(3) by an additional C¼C bond. Indeed, we observed that 5,5-dimethyl-3-(3-methylbut-3-en-1-ynyl)cyclohex-2-enone (1) a) undergoes photocyclodimerization selectively at this -additional -exocyclic C¼C bond to afford 2, and b), in the presence of 2,3-dimethylbuta-1,3-diene, affords a novel [6 þ 4] photocycloadduct 3 containing a buta-1,2,3-triene moiety (Scheme 1). We have now synthesized the two cyclohex-2-enones 4a and 4b bearing the same alkynenyl side chain at C(2) and investigated their photochemical behavior.