Every substance has the ability to induce redox characteristics (rH) to its environment, according to its chemical structure and concentration, more or less evident; in the former, the substance is bioactive. Organisms react to this induced redox character, so, we can talk about positive or negative redox mediated biological effects. The redox induced character obviously differentiates the substances submitted to this study. Natrium benzoate has the most diminished behaviour, but it express an oxidizing character of this substance. Kalium sorbate shows a stronger effect, but it has a reductive character. The acetylsalicylic acid express the most prevalent redox characteristic, but somewhat ambivalent, acting as a reductive substance in high concentrations and as an oxidizing one in low concentrations. These observations are also confirmed as a biological effect. Related to natrium benzoate, the answer of test organism (rye) is rH independent. As for kalium sorbate, this answer is intermediary while, related to acetylsalicylic acid, the later has the strongest response. Regarding to biodegradability, the situation is different. Namely, natrium benzoate shows the greatest stability when put in contact with an organism; kalium sorbate has a good stability only in its initial contact with the test organism; acetylsalicylic acid is only a little biodegraded and this with repeated recomes to initial state. This paradox of opposite behaviour can be explained by the unrecognition (incompatibility) of a synthetic substance (natrium benzoate) and by the biotic recognition of a natural substance (kalium sorbate).