Tyrosinase inhibitors are capable of preventing unfavorable enzymatic browning of fruits and vegetables. In this study, the capacity of Acacia confusa stem bark proanthocyanidins (ASBPs) to inhibit tyrosinase activity was evaluated. ASBPs were shown to be a high-potential inhibitor of tyrosinase with IC50 values of 92.49 ± 4.70 and 61.74 ± 8.93 μg/mL when using L-tyrosine and L-DOPA as the substrate, respectively. The structural elucidation performed with UV-vis, FT-IR spectroscopy, ESI-MS and thiolysis coupled to HPLC-ESI-MS suggested that ASBPs had structural heterogeneity in monomer units and interflavan linkages and consisted mainly of procyanidins dominant with B-type linkages. To gain insights into the inhibitory mechanisms of ASBPs against tyrosinase, different spectroscopic and molecular docking methods were further conducted. Results validated that ASBPs possessed the ability to chelate copper ions and could prevent the oxidation process of substrates by tyrosinase. The hydrogen bond formed with Lys-376 residue played a key role in the binding force of ASBPs with tyrosinase that induced a certain alteration in the microenvironment and secondary structure of tyrosinase, resulting in the enzymatic activity being ultimately restricted. It was also observed that ASBPs treatment effectively inhibited the activities of PPO and POD to retard the surface browning of fresh-cut asparagus lettuce and thus extended their shelf-life. The results provided preliminary evidence supporting the exploitation of ASBPs into potential antibrowning agents for the fresh-cut food industry.

Feeder cells play an important role in the culture of human pluripotent stem cells (hPSCs) in vitro. Previously, we used methanol as a fixative to prepare feeder cells for the cultivation of pluripotent stem cells (PSCs), and this method could maintain the self‐renewal and pluripotency of PSCs. However, methanol is toxic, and so here we examined whether ethanol could be used to prepare feeder cells as a fixative for hPSC culturing. Primed, naïve, and extended human embryonic stem cells and induced pluripotent stem cells can maintain self‐renewal and undifferentiated potential on feeder cells treated with ethanol for an extended period. RNA sequencing analysis showed that the expression of collagen‐related genes in hPSCs cultured on feeder cells treated with ethanol was significantly lower as compared with hPSCs cultured on feeder cells treated with mitomycin C. Therefore, we speculate that the signaling pathway mediated by collagen‐related genes may, at least in part, contribute to the maintenance of self‐renewal and pluripotency of PSCs induced by feeder cells treated with chemicals.