Abstract
Introduction: The use of natural colors is a very old practice, with evidence of use dating back about 20,000 years, which were obtained from various sources (animal, vegetable or mineral). In the standard procedure, most of the dyes used in normal or pathological staining techniques are synthetic, often difficult preparation and little storage time, involving components that, according toxicological and chemical testing, has adverse effects on health of those who work with them and the environment when discarded. Objective: This study aimed to analyze the use of natural dye extracted from the annatto (Bixa orellana L.) in histological staining of animal tissues, and standardize the methods of preparation and staining, making variations of amount of raw material, pH and temperature staining. Methods: By spectrophotometric analysis of 24 dye groups with different variables, and photomicrographs of the blades of the groups by software (Image J), we tried to determine the best parameters for the preparation and staining of histological slides with annatto dye. Results: Seed dehydration implies dye quality, as it decreased the absorbance results in the spectrophotometric analyzes of the dyes, and the mean optical density in the morphometry of the slides. Conclusion: It was concluded that the best parameters are the use of 20 g of seed at each 92,8º 100mL ethanol without addition of acetic acid, at room temperature with coloring, annatto and is an excellent substitute for eosin for histological staining.