Influence of pH and Phosphate Buffer on Inhibition of Clostridium botulinum by Antioxidants and Related Phenolic Compounds.

The compounds butylated hydroxyanisole (BHA); butylated hydroxytoluene (BHT); tert-butylhydroquinone (TBHQ); nor-dihydroguaiaretic acid (NDGA); 2', 4', 5'-trihydroxybutyrophenone (THBP); 8-hydroxyquinoline; isoamyl and isobutyl esters of gallic acid; ethyl, propyl, and butyl esters of p-hydroxybenzoic acid; thymol; 2-isopropylphenol; 2-tert-butylphenol; and 2-tert-butyl-4-methylphenol were tested for their antibotulinal activity in prereduced Thiotone-yeast extract-glucose (TYG) broth with and without hosphate buffer (0.05 M, pH 6.0 and 7.0). Isoamyl gallate, isobutyl gallate, propyl ester of p-hydroxybenzoic acid, NDGA, BHA, 8-hydroxyguinoline, and 2-tert-butylphenol were more inhibitory when phosphate buffer (pH 7.0(was added to prereduced TYG. The propyl and butyl esters of p-hydroxybenzoic acid and 2-isopropylphenol were more effective at pH 6.0 than at pH 7.0, whereas thymol and 8-hydroxyquinoline were slightly more active at pH 7.0 than at pH 6.0 NDGA at 50 μg/ml was the most effective compound tested for delaying growth and toxin production.