Benzene
Benzene (C6H6) is a colorless, volatile liquid with a rather pleasant odor.
Benzene is toxic when it gains access to the body by any route. Poisoning commonly occurs, however, as a result of the inhalation of the vapors. Notwithstanding its insidious toxicity, benzene continues to be extensively used in the petroleum, explosive, plastics, pesticide, and other industries. It has no therapeutic uses.
Benzoic acid (C6H5COOH).
Benzoic acid has been widely used as a food preservative. In a concentration of 0.1% it prevents bacterial and fungal growth if the medium is slightly acidic. Benzoic acid is relatively nontoxic and almost tasteless and for these reasons it can be added to food.
After ingestion, the benzoic acid is conjugated with glycine and excreted in the urine as hippuric acid (C6H5CONH-CH2-COOH).
Sodium benzoate (C6H5COONa) is used as a drug for cough.
p-Aminobenzoic acid (4-aminobenzoic acid, PABA)
Para-aminobenzoic acid has the interesting property of neutralizing the bacteriostatic action of sulfonamide drugs. PABA has been included as a member of the vitamin B complex.
PABA is a vitamin-like substance and a growth factor required by several types of microorganisms. In bacteria, PABA is used in the synthesis of the vitamin folic acid. Although a structural unit of folic acid, PABA is not considered a vitamin.
The mammalian organismisincapable of converting PABA to folic acid and the folic requirements of mammals must thereforebemet with performed folic acid. Thus, there is no evidence that PABA is a dietary essential in man.