The Staining Interactions of Aqueous Extract of Skin Allium cepa (Red Onion) on Some Selected Histological Tissues

Introduction: Histological stains are biological dyes which colour tissue in order to aid optical differentiation of tissue component. Dyes are coloured substance which impact colour for material such as textile, cosmetic, food, drugs, rubber plastics, hair, fur and tissues. There are two types of dyes namely; natural dyes and synthetic dyes. Allium cepa is an imperative, evergreen plant, which belongs to the family Amaryllidaceace commonly called bulb onion.

Aim: This research work aimed at evaluating the staining capability of onion extract as counter stain when haematoxylin was used as primary stain.

Methods: Tissue blocks sections of liver and kidney organs were made from the Wistar rat. Serial sections labelled A to M were made from each block and stained with Harris haematoxylin. Section A was counterstained with eosin, as control. Different preparations of extracts of the onion skin were used to counter stain sections of kidney and liver tissues. Group B to Mwere kidney and liver tissues stained as follows: B, E, H and K (5% aqueous and ethanolic extract with ferric chloride, 5% aqueous and ethanolic extract with potassium aluminium alum, and 5% aqueous and ethanolic extract without mordant, for 10 and 20 minutes). C, D, F, G, I, J, L and M (5% aqueous and ethanolic extract with ferric chloride, 5% aqueous and ethanolic extract with potassium aluminium alum and 5% aqueous and ethanolic extract without mordant for 10 and 20 minutes).

Results: The skin extract of Allium cepa stained the cytoplasm of cells and connective tissues in shades of reddish brown to yellowish brown. The study established the cytoplasmic counter-staining ability of the extract of Allium cepa.

Conclusion: It is therefore suggested that onion skin extract solution can be substituted for eosin due to its domestic availability, ease of preparation and above all, its good cytoplasm contrast with the nuclear stain.