Fluorescence study on the nyctinasty of Cassia mimosoides L. using novel fluorescence-labeled probe compounds

We synthesized fluorescence-labeled probe compounds bearing 6-((7-amino-4-methylcoumarin-3-acetyl)amino)-hexanoyl (AMCA, 1), 6-N-(7-nitrobenz-2-oxa-1, 3-diazol-4-yl)-aminohexanoyl (NBD, 2), and 6-(4-((5-dimethylaminonaphthalene-1-sulfonyl)amino))-hexanoyl (dansyl, 3) groups as the fluorescent functionality. In these probe compounds, NBD-type probe, 2, showed leaf-opening activity at 5 X 10(-6) M. The bioactivity of 2 is one-fifth as strong as that of the natural product, potassium isolespedezate (6). We carried out the binding experiment using 1 in a plant body. Then, it was suggested that fluorescence-labeled probe compound directly bound to a motor cell in pulvina of Cassia mimosoides. And this binding was specific to C. mimosoides. Probe compounds cannot bind plant sections of other nyctinastic plants. (C) 2001 Elsevier Science Ltd. All rights reserved.