ABSTRACT
Clearing agents are among the most noxious and hazardous chemicals found in histology laboratories. Xylene has probably been the most commonly used chemical in the histology laboratory despite its hazards. There has been several laboratory tests to replace xylene as clearing agent but most of these commercially available substitutes in some cases are less effective, more expensive, slightly biodegradable and are not readily available than xylene itself. The present study was aimed at evaluating the clearing abilities of some nontoxic concentrated hydrophobic liquids commonly called essential oils namely citrus oil, citrodora oil, and neem oil during histological processing of some selected organs of adults Wistar rats. The three essential oils were used alongside xylene to clear livers, kidneys, Brains, testes and intestinal tissues of Wistar rats. The citrus oil was extracted from the peels of citrus oranges by hydro distillation, while the citrodora oil was extracted from the leaves of eucalyptus plants by hydro distillation method. The neem oil was extracted from the seeds of neem tree by Cold n-hexane method. Physical properties, the phytochemical and Gas Chromatography-Mass Spectroscopy (GC-MS) studies of the oils were carried out using the methods of Siddiqui and Alli, (1997); Tresae, (1989) and Ladan, (2011) respectively. The tissues were histologically processed using the method of Bancroft and Stevens (2008). The result showed that citrus oil and xylene were colorless while citrodora oil was pale yellow and neem oil was dark brown. The densities of the oils are 0.80 g/ml for citrus oil, 0.80g/ml for citrodora oil, and 0.89 g/ml for neem oil when compared to 0.84 g/ml of xylene. The viscosity of neem oil was 36cp when compared to that of citrus oil which was 0.35cp, citrodora oil 0.34cp and xylene 0.45cp. It was also demonstrated that neem oil has the highest value of flash point at 108 0C while citrus and citrodora oils had similar flash points at 340C and 350C respectively and xylene had flash point at 390C. The oils had refractive indexes of 1.46, xvi 1.46, 1.47 and 1.50 for citrus, citrodora, neem oil and xylene respectively. Histological observation showed that the cytoplasmic and nuclear staining ability appeared to give good contrast in citrodora oil followed by citrus oil when compared with xylene. Significant changes in the section and staining ability were observed in the neem oil cleared sections when compared to xylene, citrus and citrodora oil (p?0.05). The result of the present study showed that the three essential oils used in this work can clear tissues substantially well. Citrodora oil appeared to be better followed by citrus oil while the neem oil had the least ability to clear tissue properly.