Norbixin is a dicarboxylic water-soluble carotenoid present in the pericarp of the achiote (Bixa orellana L.) seed. Annatto is commonly used by the food and cosmetic industries as a natural pigment. The aim of this study was to evaluate the healing process of open dermal wounds of rats treated with an aqueous solution of annatto containing 2.5% of norbixin carried out by histomorphometric analysis. For this end, cutaneous wounds were made on the back of 32 male Wistar rats. The wounds were treated with annatto solution (experimental group, n = 16) and saline solution 0.9% (control group, n = 16). At 3, 7, 14 and 21 days after the surgical procedure, the animals were sacrificed. After histological preparation, the histological material was submitted to the staining technique with hematoxylin-eosin for the counting of inflammatory cells and fibroblasts, with toluidine blue 1% for mast cell counting and with picrosirius red for the total collagen fibers. The images of those histological slides were captured by a digital camera connected to an optical microscope, with fixed focal length and clear field; 10 fields were captured from each slide with final zoom of 400X. The photomicrographs were analyzed by the ImageJ software. The results were submitted to the Student's t-test and the value of p < 0.05 was considered as relevant. The topical treatment with the annatto solution increased the inflammatory infiltrate during the 3rd, 14th and 21st days after surgery. The experimental group presented increased vascular density compared to the control group after the 7th day and a smaller amount of fibroblasts up to the 14th day after surgery. We concluded that the annatto solution containing 2.5% of norbixin is not innocuous to skin tissues and has proinflammatory and proangiogenic effects during the process of skin wound healing in rats, interfering in the physiological healing process.
histology; annatto; ulcers; skin
