Applicability of eucalyptus wood waste extracts for the histological staining of connective tissue

Biological staining of tissue is a crucial procedure in histotechnology. Rudimentary methods for section preparation have often used stains from natural products, although use of synthetic dyes has become the contemporary standard. Artificial dyes increase the operating costs of a laboratory as well as increase the environmental and personnel risks during manufacturing and usage. These considerations have stimulated research to find alternative natural stains from the wide diversity of plant species. The present study investigated the effect of Eucalyptus sp. (Myrtaceae) wood waste extract on histological staining of animal tissues, using a series of pigment concentrations, pH conditions, and temperatures. Eucalyptus wooden slivers were dried, milled, and 1 g, 2 g, and 4 g of the fine powder was subjected to 50% ethanol extraction for 2 days. Staining tests were then performed on formalin fixed paraffin embedded (FFPE) sections. Increasing acetic acid concentrations (1%, 2% and 4%) were added to the extracts and compared to an acid-free extract. Staining was performed at both ambient room temperature (RT) and 60°C. Connective tissue acidophilic components were well-contrasted and a hematoxylin counterstain demonstrated distinct structural differences between matrix and cell nuclei. Therefore, the present findings demonstrate the potential utility of the eucalyptus wood extracts application as a natural stain alternative for routine histology.