These observations suggested that citrulline accumulation may be regulated in a distinct manner from other nutrients during watermelon fruit maturation. © 2016 Society of Chemical Industry.

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Natural products isolation using protein based methods is an attractive for obtaining bioactive compounds. To discover neural stem cell (NSC) differentiation activators, we isolated eight inhibitors of Hes1 dimer formation from Psidium guajava using the Hes1-Hes1 interaction fluorescent plate assay and one inhibitor from Terminalia chebula using the Hes1-immobilized beads method. Of the isolated compounds, gallic acid (8) and 4-O-(4"-O-galloyl-α-L-rhamnopyranosyl)ellagic acid (11) showed potent Hes1 dimer formation inhibitory activity, with IC 50 values of 10.3 and 2.53 μM, respectively. Compound 11 accelerated the differentiation activity of C17.2 NSC cells dose dependently, increasing the number of neurons with a 125% increase (5 μM) compared to the control.Neurodegenerative diseases such as dementia and spinal cord injury severely compromise the quality of life. The discovery of neural stem cells (NSCs) in human adult brain 1,2 led to the expectation of novel treatments involving NSC transplantation or accelerated differentiation of internal NSCs in the brain to overcome neurodegenerative diseases. However, the development of these approaches and small molecule NSC activators has been slow, possibly due to the complex mechanism underlying the differentiation of NSCs to neural cells.Basic helix-loop-helix (bHLH) factors play crucial roles in the differentiation of neural cells such as neurons, astrocytes and oligodendrocytes 3 . For example, proneural bHLH factors, such as Ascl1 (formerly Mash1), Neurog1 and Neurog2 regulate the generation of neurons. Olig1 and Olig2 are bHLH factors important for the maturation of oligodendrocytes. Hairy and enhancer of split (hes) bHLH factors promote the self-renewal of NSCs and the generation of astrocytes, as well as inhibiting the differentiation of NSCs by suppressing the expression of proneural genes. Recently, Kageyama et al. reported that oscillation in the concentration of bHLH factors directly controls the fate of NSCs 4,5 . Hes1 and Ascl1 proteins oscillate with 2-to 3-hour periods, whereas Olig2 oscillates with a 5-to 8-hour period. During cell fate choice, one bHLH factor is expressed in a sustained manner while the others are repressed. In neurons, Ascl1 is expressed sustainably while Hes1 and Olig2 expression is inhibited.Hes1 dimerizes and binds to the promoter region of Ascl1 and other proneural genes (Fig. 1), making the inhibition of Hes1 an attractive approach to enhance neuronal differentiation. If the interested target protein was decided, it would be faster and effective to isolate the bioactive natural products using a "protein-based assay system" 6 . However, the number of reports of isolation using protein-based assay system was still limited (affinity chromatography 7-9 , protein-immobilized beads 10-18 , ultrafiltration 19-21 , and protein-protein interactions 22,23 ). In our attempts to find Hes1 inhibitors effectively, we constructed a new Hes1-Hes1 interaction fluorescent plate assay which gave the first Hes1 dimer inhibitors 24 . Also, we have...

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Phosphonylation of kojic acid has been achieved using inorganic diphosphonate (DP) in aqueous solution. The optimum condition for the phosphonylation of kojic acid with DP is kojic acid : DP = 0.1 mol/L : 0.5 mol/L, pH 9 and 25 ºC. 2-Phosphonylmethyl-kojic acid was synthesized with the yield of 45 %. The reaction mechanism of kojic acid with DP was discussed. We have successfully introduced the phosphonate group in kojic acid. Phosphonylated kojic acid is expected that the permeability of kojic acid into the skin will be increased by introducing a phosphonate group.