Tryptanthrin derivatives, which are known antimicrobial agents, were synthesized, and their absorption and fluorescence spectral behaviors were investigated. Our results showed that 2-aminotryptanthrin exhibits both a high fluorescence quantum yield and large positive fluorescent solvatochromism.

1385Tryptanthrin (T, Fig. 1a) is a weak basic alkaloid formed in a number of plant species.1 This compound possesses antibacterial activity against a variety of pathogenic bacteria.2 However, the optical absorption and fluorescence properties of T and its derivatives have never been reported. Recently, we investigated the optical absorption and fluorescence properties of T and its derivatives. As results of measurements of their UV-vis absorption and fluorescence spectra, we found that 2-aminotryptanthrin (T2NH2, Fig. 1b) had excellent photophysical properties, such as wide-wavelength absorption and emission, and a high fluorescence quantum yield (Φf = 0.5 in acetonitrile).3 T2NH2 will become a good energy acceptor for FRET (fluorescence resonance energy transfer), 4,5 compatible with an energy donor having a wide excitation wavelength range of over 300 nm.FRET is defined as an excited-state energy interaction between two fluorophores in which excited donor energy is transferred to an acceptor part without any photon-emission. 4,5 FRET thus requires a certain degree of spectral overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor. In pursuit of FRET-based metal cation sensors, we report here a new receptor, 1-(2-tryptanthrinylaminoacetoxy)-14-(1-pyrenecarboxy)-3,6,9,12-tetraoxatetradecane (T2NH-P5P, Fig. 1c), in which a pyrene group as an energy donor and a 2-aminotryptanthrin unit as energy acceptor are anchored with pentaethyleneglycol, displaying change in the FRET behavior upon Al 3+ addition. T2NH-P5P was obtained in four steps. The electron-spray ionization mass spectra of T2NH-P5P showed corresponding molecular ion peaks, and the NMR spectra were appropriate for the compound.6 A stock solution of T2NH-P5P was prepared by dissolving a weighed amount of T2NH-P5P in acetonitrile.The titration of T2NH-P5P ([T2NH-P5P] = 1 μM, M = mol dm -3 ) against metal-ion solutions was performed in a spectro photometric cell of 1-cm path length. The UV-vis spectra (between 200 and 600 nm) of the resulting solutions were recorded at room temperature with a JASCO V-670 spectrophotometer after the addition of each metal salt: Ca(ClO4)2, Ba(ClO4)2, Zn(ClO4)2, and Al(ClO4)3. The fluorescence spectra were measured between 350 and 700 nm with a Hitachi F-4500 fluorometer using an excitation wavelength of 325 nm. Titrations were performed with metal ions (10 -1000 μM) as a titrant and T2NH-P5P (1 μM) as a titrate. The metal-ion sources were identical to those used to 2009 © The Japan Society for Analytical Chemistry † To whom correspondence should be addressed. E-mail: jun@cc.hirosaki-u.ac.jp 2-aminotryptanthrin Derivative with Pyrene as a FrET-based Fluorescent chemosensor for al 3+Jun kawakami,* † kenta kikucHi,* kazunori cHiba,* Noriyuki maTsusHima,* asako yamaya,* shunji iTo,* masahiko Nagaki,* and Haruo kiTaHara** * Graduate School of Science and Technology, Hirosaki University, Hirosaki, Japan ** Department of Natural Science, Faculty of Education, Hirosaki University, Hirosaki,, Ja...

Enhancement of cardiac differentiation is critical to stem cell transplantation therapy for severe ischemic heart disease. The aim of this study was to investigate whether several derivatives of tryptanthrin (1), extracted from the medicinal plant Polygonum tinctorium, induce the differentiation of P19CL6 mouse embryonal carcinoma cells into beating cardiomyocyte-like cells. P19CL6 cells were cultured in α-MEM supplemented with 10% FBS including a test compound or vehicle. Drug-induced differentiation was assessed by measuring the number of beating and nonbeating aggregates and the area of beating aggregates, and the expression of genes involved in cardiac differentiation was evaluated by real-time PCR. A 1 μM concentration of 8-methyltryptanthrin (2) induced the differentiation of P19CL6 cells into cardiomyocyte-like cells to a significantly greater degree than 1% dimethyl sulfoxide (DMSO), a conventional differentiation inducer of P19CL6 cells. Furthermore, 2 strongly increased both the number and the area of spontaneously beating aggregates in comparison with DMSO. Two distinct genes of the calcium channel family, Cav1.2 and Cav3.1, underlying cardiac automaticity were significantly expressed in the presence of 2. Gap junction genes GJA1 and GJA5 contributing to the synchronized contraction of the myocardium were also induced significantly by 2. These results suggest that 2 successfully differentiated P19CL6 cells into spontaneously beating cardiomyocyte-like cells by activating the gene expression of pacemaker channels and gap junctions.