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Long-term high sugar accelerates skin ageing via glycosylation. In this study, microalgae-derived active compounds were investigated for their potentially beneficial effects on skin ageing. Two carotenoids, namely astaxanthin (in the form of either monoester or diester) and lutein, were separated from the green alga Haematococcus pluvialis. These carotenoid fractions significantly attenuated the high glucose (HG)-induced cell injury and oxidative stress. They also inhibited the formation of Nε-Carboxymethyllysine (CML), a typical product of glycosylation. The degradation of collagen I and III caused by HG was substantially recovered, in which astaxanthin monoester exhibited the most prominent effect. This was attributed to the down-regulation of matrix metalloproteinase (MMP)-2 mRNA expression. Through proteomics analyses, six hub proteins were identified, which work as highly connected nodes in the protective effects of astaxanthin monoester against HG stress. These findings strongly suggest the benefits of microalgae-derived carotenoids in alleviating HG-induced skin ageing.

Oxyresveratrol (Oxy) has attracted much attention by employing it as an antibrowning agent in fruits and vegetables. In this study, the formation of cyclodextrin (CD) inclusion exhibited a certain protective effect on Oxy oxidative degradation, while hydroxypropyl-β-cyclodextrin (HP–β-CD) inclusion complex showed stronger stabilizing effects than those of β-cyclodextrin (β-CD). The combined use of CD and hydroxypropyl methylcellulose (HPMC) greatly improved the stability of Oxy–CD inclusion complexes, with approximately 70% of the trans-Oxy retained after 30 days of storage under light conditions at 25 °C. The results of the interaction between CD and Oxy determined by phase solubility studies and fluorescence spectroscopic analysis showed that the binding strength of CD and Oxy increased in the presence of HPMC. Moreover, Oxy combined with ascorbic acid and HPMC showed an excellent antibrowning effect on fresh-cut apple slices during the 48 h test period, indicating that adding HPMC as the third component will not influence the antibrowning activity of Oxy.