Antimicrobial compounds against bacteria

Other Nitrogen Compounds. The basis of the sophisticated nitrogen compounds Hsted in Table 10 is the reaction of formaldehyde with amino compounds. A significant amount of Hterature details investigation of the mechanism of action, particularly whether or not the antimicrobial activity depends on decomposition to formaldehyde (40—42). These compounds tend to have substantial water solubiUty and are more effective against bacteria than fungi and yeasts. Key markets for these compounds are metalworking fluids, cosmetics, and in-can preservation of paints (see Alkanolamines Amines, fatty amines). 

A tree, Scorodocarpus borneensis, native to Borneo and the Malay peninsula, has a garlic-like smell and is known as wood garlic . The fruit is used locally for seasoning. The major volatile flavor compounds from wood garlic are similar to those of garlic itself. Some of these materials are polysulfur compounds and have antimicrobial activity against some bacteria and fungi. These materials contain four sulfur atoms.75 They are either 2,4,6-trithiaheptane-5-thione-2,2-dioxide (CH3-SO2-CH2-S-CS-S-CH3) or derivatives of tetrathia-octane (CH3-S-CH2-S-S-CH2-S-CH 3, CH3-SO2-CH2-S-S-CH2-S-CH3, CH3-S-CH2-SO2-S-CH2-S-CH3). 

Newly synthesized compounds 22, 23, 25c-e, 26d and 29e were screened in vitro for their antimicrobial activities against Gram positive bacteria Staphylococcus aureus (NCTC-7447), Bacillus cereus (ATCC-14579) and Gram negative bacteria Serratia marcesens (IMRU-70) and Proteus merabitis (NTCC-289) using the paper disk diffusion method for the antibiotic sensitivity technique [60]. The tested compounds were dissolved in N,N-dimclhylformamidc (DMF) to obtain a 1 mg/mL solution. The inhibition zones of microbial growth produced by different compounds were measured in millimeters at the end of an incubation period of 48 h at 28 °C. DMF alone showed no inhibition zone. 

A series of benzoxazines (131-139) were isolated [117] from fermentation broth of S. rimosus. These compounds were found to inhibit bacterial histidine kinase and were produced by a controlled cultivation with added NaBr and Nal. As mentioned above, streptopyrol (131) inhibits the nitrogen regulator II histidine kinase from Escherichia coli with IC o of 20 pM and exhibits antimicrobial activity against a wide range of bacteria and fungi. 

Many antimicrobial products that were formerly used with textiles are now strictly regulated because of their toxicity and potential for environmental damage. Products such as copper naphthenate, copper-8-quinolinate, and numerous organo mercury compounds fall into this category. Other materials that still have limited use in specialised areas include tributyl tin oxide (deleted in many countries. Fig. 15.1a), dichlorophene (Fig. 15.1b) and 3-iodopropynylbutyl carbamate (Fig. 15.1c). These products typically show a very broad spectrum of activity against bacteria and fungi, but suffer from application and durability problems. 

Antimicrobial activity benzyl alcohol is bacteriostatic and is used as an antimicrobial preservative against Gram-positive bacteria, molds, fungi, and yeasts, although it possesses only modest bactericidal properties. Optimum activity occurs at pH below 5 little activity is shown above pH 8. Antimicrobial activity is reduced in the presence of nonionic surfactants, such as polysorbate 80. However, the reduction in activity is less than is the case with either hydroxybenzo-ate esters or quaternary ammonium compounds. The activity of benzyl alcohol may also be reduced by incompatibilities with some packaging materials, particularly polyethylene see Section 12. 

More recently, Cha et al. [82] investigated the chemical composition and antimicrobial activity of the essential oils of Artemisia scoparia and Artemisia capillaris Thunb. The essential oil from Artemisia scoparia was rich in camphor. Fig. (1), 1,8-cineole, Fig. (2) and (3-caryophyllene. Fig. (3) as the major compounds, whereas Artemisia capillaris oil was rich in 3-pinene. Fig. (6), P-caryophyllene, Fig. (3) and capillene. The essential oils and some of their major compounds were tested for their antimicrobial activity against 15 different genera of oral bacteria. The essential oils exhibited considerable inhibitory effect against all the oral bacteria tested, while the major components demonstrated various degrees of growth inhibition. 

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