The antimicrobial quaternary ammonium salts, which were invented by Domagk in 1935, have very widely been used as a disinfectant in medical supplies, hospital environmental sanitation and antimicrobial treated industrial products in all over the world. The N-alkylpyridinium iodide was chosen for the molecular design of the optimization of quaternary ammonium salt structure as a lead chemical compound. The quantitative structure-activity relationship between antimicrobial activity and molecular structure was analyzed using molecular hydrophobicity, chemical shift of ¹H and ¹³C, acid dissociation constant and bacterial cell surface hydrophobicity as a parameter. On the basis of these results, it succeeded in the development of the new quaternary ammonium salts with the symmetrical unique structure with two pyridinium residues in the molecule. The quaternary ammonium salts with gemini structure have antimicrobial activity which is stronger than the mono type quaternary ammonium salts with one pyridinium residue in the molecule against bacteria, molds and yeasts, and have strong microbioclastic activity. The antimicrobial activity of the gemini type quaternary ammonium salts does not be affected by coexistence protein, environmental pH, and temperature. From these results, it was clarified that the gemini quaternary ammonium salts have the excellent property, which does not make drug resistant microbes.

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Metabolism of n-3 polyenoic fatty acid have been recognized to be a dominant factor in health and diseases in humans. Recently attention focuses on perilla seed oil as edible oil and dietary supplement of n-3 acids which give an appropriate n-6 : n-3 ratio in dietary polyenoic fatty acids, though there is no consistency in its appropriate ratio among the investigators. On the other hand, the potential applications of perilla oil are limited by an insufficiency of the oxidative stability due to high degree of unsaturation. This review mainly describes the recent advances in the studies of the lipid nutrition focused on n-3 acids and works on the oxidative stabilities of the seed oil of perilla frutescens, including the preventive countermeasures to the oxidative deterioration of perilla seed oil, in order to make better use of perilla seeds and its oil for dietary purposes such as a dressing and modified fats for breads. We found that refregeration, shading, and/or addition of the antioxidants such as tea leaf catechins extremely increases the oxidative stabilities of perilla oil. The effect of mixed tocopherols and ascorbyl palmitate was insufficient to prevent the autoxidation of perilla oil. The perilla seeds also may be utilized as excellent foodstuff, which contain enough n-3 fatty oil, polyphenols and dietary fiber.

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