Abstract |
The photoprotolytic processes of 7-hydroxy-coumarin (Umb) were investigated by steady-state and time-resolved-fluorescence techniques. We found that the Umb compound is a photoacid with pK(a)* ≈ 0.4 and a rate constant of the excited-state proton transfer (ESPT) to water of 2 × 10(10) s(-1). Umb is also a photobase and accepts an excess proton in solution and also directly from weak acids like acetic acid. When Umb is adsorbed on cellulose it also functions as a photoacid and a photobase. Hydroxycoumarins are known to accumulate next to fungal-, bacterial-, and viral-infected regions in the leaves and stems of plants in general and also in trees. We propose that these compounds when irradiated by sunlight UV, combat the fungi or bacteria by excited-state proton-transfer reactions. These photoprotolytic reactions provide a universal resistance mechanism to infections in plants.
|
Authors | Ron Simkovitch, Dan Huppert |
Journal | The journal of physical chemistry. B
(J Phys Chem B)
Vol. 119
Issue 46
Pg. 14683-96
(Nov 19 2015)
ISSN: 1520-5207 [Electronic] United States |
PMID | 26488429
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
|
Chemical References |
- Umbelliferones
- 7-hydroxycoumarin
|
Topics |
- Light
- Mycoses
(prevention & control)
- Proteolysis
- Spectrometry, Fluorescence
- Umbelliferones
(metabolism)
|