In recent years, various diseases have been linked to protein oxidation, changing their biological function due to the formation of carbonyl groups. The objective of this research is to evaluate the inhibition of carbonylation by the acetone extract of hawthorn (Crataegus Mexicana) in human plasma proteins in vitro inducing oxidative stress by iron sulfate. The quantification of carbonyl groups was developed by spectrophotometric technique using 2,4-dinitrophenylhydrazine (DNPH).We worked with 6 clinically healthy people. Three concentrations of the acetone extract of hawthorn (C. mexicana) were used at 10, 100 and 1000 mg/L. The concentration of 1000 mg/L of the extract of hawthorn presented greater inhibition in the carbonylation of proteins with more than 50%.