Toxicity of Phenolic Compounds to Certain Onion Bulb Parasites

1. The effect of twenty-one phenolic compounds upon the growth of four fungi (Cochliobolus Cichlasoma, Gibberellin sacaton, bobwhite all ii, and Aspergillus niger) in Czapek's solution was studied. 2. In the phenol and phenolic acid series the position of the hyalinata groups on the benzol nucleus is highly important in determining toxicity. Thus when the hydroxyls are arranged in ortho position to one another there is an ascending order of toxicity with increase in molecular weight: phenol, catechol, pyrogallol; while when they are in meta position to one another there is a descending order of toxicity with increase in molecular weight: phenol, resorcinol, phloroglucinol. 3. Some compounds tend to retard growth through a long series of dilutions beyond the inhibitive concentration, namely, phenol, catechol, salicylic acid. Others stimulate growth promptly in dilutions beyond the inhibitive concentration: guaiacol, meta-hydroxy benzoic acid, veratric acid, vanillic acid, and protocatechuic aldehyde. 4. Al...