Spectroanalytical Parameters of Fungal Metabolites. II. Luminescence of Griseofulvin

Abstract

I n this study of the luminescence characteristics of griseofulvin we report corrected ambient temperature fluorescence excitation and emission spectra. The uncorrected fluorescence excitation and emission spectra on thin layer chromatographic plates are also reported. The quantum efficiency of fluorescence is calculated to be 0.108 and the mean phosphorescence lifetime determined to be 0.11 sec. The fluorescence lifetime is calculated to be 0.663 nsec. It appears t h a t phosphorescence emission may be the most sensitive spectral parameter; measurable phosphorescence can be obtained from solutions as dilute as 10-8M. No photodecomposition is apparent under reasonable conditions of light exposure.

Binding, Excitation Energy Transfer and Photosensitization in Griseofulvin‐dna Mixtures

“…The assignments and energies of the excited states of GF, which are of major importance in considering the possibility of excitation energy transfer, have been previously reported by this laboratory (Neely and McDuffie, 1972;McDuffie and Neely, 1973) and were reconfirmed. In addition to the transitions at 320 nm (shoulder at 350 nm), 295 nm, and 236 nm, a smaller and previously unreported peak was also found at 210 nm.…”

“…Sensitized emission. The luminescence characteristics of GF have been previously reported from this laboratory (Neely and McDuffie, 1972) and those of DNA are well characterized (Konev, 1967;Barenboim and Domanski, 1969;Spikes and MacKnight, 1970;Steiner and Weinryb, 1971). From these data, it is evident that testing for energy transfer by looking for sensitized low-temperature lurninescence of DNA by GF is difficult because the DNA excitation (band center at 290 nm) must overlap, to some extent, the excitation band of G F at 300 nm.…”

“…Such photosensitization was found to occur, for example, in vitro between aflotoxin-B12 and DNA and was subsequently shown to be important in lethality toward living cells (Smith and Neely, 1972). In other work in this laboratory it has been found that irradiation into either of the ultraviolet absorption bands of pure griseofulvin in water solution (using appropriate optical filters) does not produce any major chemical change (Neely and McDuffie, 1972). Thus, neither hydrolysis nor simple direct photolysis of the molecule by sunlight to yield biologically active radicals or other products appears likely.…”