The antimicrobial activity of honokiol and magnolol, the main constituents of Magnolia officinalis was investigated. The antimicrobial activity was assayed by the agar dilution method using brain heart infusion medium and the minimum inhibitory concentration (MIC) were determined for each compound using a twofold serial dilution assay. The results showed that honokiol and magnolol have a marked antimicrobial effect (MIC = 25 microg/mL) against Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Micrococcus luteus and Bacillus subtilis, but did not show antimicrobial activity (MIC > or = 100 microg/mL) for Shigella flexneii, Staphylococcus epidermidis, Enterobacter aerogenes, Proteus vulgaris, Escherichia coli and Pseudomonas aeruginosa. Our results indicate that honokiol and magnolol, although less potent than tetracycline, show a significant antimicrobial activity for periodontal pathogens. Hence we suggest that honokiol and magnolol might have the potential to be an adjunct in the treatment of periodontitis.

A purified preparation of pyocin B39 was shown to be homogeneous by disc electrophoresis and ultracentrifugation. Pyocin B39 is an antibacterial agent, protein in nature, and is capable of inhibiting the growth of susceptible cells. It caused a susceptible strain of Pseudomonas aeruginosa to release ultraviolet-absorbing material. Pyocin B39 appears to be a protein with a high molecular weight; its sedimentation coefficient is 32.8S. It was destroyed by 7 M urea but was resistant to attack by proteolytic enzymes, such as pepsin and trypsin. From its sedimentation coefficient, a molecular weight of about 2 X 106 was calculated. An electron photomicrograph of pyocin B39 revealed it as a rodlike particle, 7.50 pm long and 1.08 pm wide, with striations running at nearly right angles to the axes of the particle.Bacteriocins are highly specific antibiotics produced by many bacteria and are active against the same or related strains. Many bacteriocins have been described and classified, but only a few of them have been studied in detail (17). The characteristic property of bacteriocins is their ability to kill susceptible cells but not to multiply within them. The ability to produce bacteriocins and sensitivity towards them are under genetic control (5). Small amounts of bacteriocins are produced by cultures of bacteriocinogenic strains. If, however, the culture is irradiated with an optimal dose of ultraviolet light, the cells are apparently induced to produce synthetic bacteriocin.Pyocin, a bacteriocin of Pseudomonas aeruginosa, was first reported by Jacob (8), who showed that pyocin, like colicin, exerted a bactericidal effect on susceptible cells. On the other hand, it was found by Kageyama et al. (10,11) that pyocin R was induced from strain R of P. aeruginosa by ultraviolet light or mitomycin C. They succeeded in purifying pyocin R by ultracentrifugation and diethylaminoethyl cellulose chromatography. Purified pyocin R is a rodlike particle with a molecular weight of about 107 (S20o , 90.5S). The fine structure of pyocin R was investigated by Ishii et al. (7) by the negativestaining technique of electron microscopy, and it was found that the structure of pyocin R was remarkably similar to that of the tail of T-even bacteriophage. Biosynthesis of pyocin R, together with the chemical and biological changes in the bacterial cells after induction, was investigated by Ikeda et al. (6) by the incorporation of 35S-amino acid into pyocin molecules.It was the aim of the present work to investigate further the physical and chemical properties of pyocin B39 reported previously (2).MATERIALS AND METHODS Bacterial strains. P. aeruginosa B39, a pyocinogenic strain, was used for preparation of pyocin B39. This strain was obtained through the courtesy of M. T. Parker of the Cross Infection Reference Laboratory, Central Public Health Laboratory, London, England. A pyocin-susceptible strain was selected by susceptibility tests from the Department of Bacteriology and Serology, Veterans General Hospital, VACRS, Taipei, Taiwan, Repu...