Yukinori Yamauchi and Masayuki Kuzuya*

Laboratory of Pharmaceutical Physical Chemistry, Gifu Pharmaceutical University
5-6-1, Mitahora-higashi, Gifu 502-8585, Japan
kuzuya@gifu-pu.ac.jp

A number of ESR studies of stable free radicals generated in a variety of solid state carbohydrates by X-, b, and UV-ray radiation have been reported. This reflects, in part, interest in the important physiological roles of these compounds in living systems.

As a part of our continuing work on elucidation of plasma-induced radicals of carbohydrates [1-5], we report here the special features of plasma-induced radicals of monocarbohydrates, a- and b-glucose. Argon plasma-irradiation gives ESR spectra considerably different from those of polycarbohydrates. The simulated spectra disclosed that the observed spectra of a-glucose consist of four kinds of discrete spectral components, one isotropic spectrum [doublets (I) ], assigned to hydroxylalkyl radicals and two anisotropic spectra [doublet (II) ], doublet of doublets (IV) ], both being assigned to an acylalkyl radical, and a smeared-out single line spectrum (V), assigned to a dangling-bond site (DBS). All these component radicals are essentially identical to those of plasma-irradiated maltose. On the other hand, those of b-glucose consist of five kinds of discrete spectral components, I, II, IV, V and the triplet spectrum (III) with ca.3.7 mT of HSC present only in b-glucose, which is assignable to the hydroxylalkyl radical of the glucose units.

The special feature here is the fact that the spectrum (V) is a minor component, contrary to polycarbohydrates. It was also shown that, though the spectral intensities of mono-carbohydrates were leveled off for shorter plasma duration, the decay rate of their radicals on standing at room temperature was much lower than that of polycarbohydrates.

It was also shown that monocarbohydrate radicals which are stable even after prolonged standing in air at room temperature unlike polycarbohydrates. It is clear that oxygen under atmospheric pressure can not diffuse to the tight hydrogen bonding network in the crystalline state of monocarbohydrates.

References

1. M. Kuzuya et al., J. Am. Chem. Soc., 114, 6505 (1992).
2. M. Kuzuya et al., J. Photopolym. Sci. Technol., 6, 371 (1993).
3. M. Kuzuya et al., J. Phys. Chem., 98, 11301 (1994).
4. M. Kuzuya et al., Chem. Pharm. Bull., 43, 2037 (1995).
5. M. Kuzuya et al., Thin Solid Films, (in press).