Abstract—This study was conducted to investigate the effect of the leaf essential oil of C. sinensis harvested at 7.00a.m and 4.00p.m on some Liver and Kidney function indices of diabetic rats as well as investigate the effect of time of harvest on the observed effect. Experimental animals were divided into 4 groups (A, B, C and D). Diabetes mellitus was induced in all animals, except the normal control group (Group A), by injecting 150mg/kg body weight of alloxan monohydrate intraperitoneally. Group A received distilled water while group B (diabetic control group) was not treated. Group C and D were treated with leaf essential oil of C. sinensis harvested at 7.00 a.m and 4.00p.m respectively at a dose of 110 mg/kg body weight every other day for 15 days. Alkaline phosphatase (ALP), Alanine Transaminase (ALT) and Aspartate Transaminase (AST) activity was evaluated in the serum, Liver and Kidney of studied animals. Total and Direct Bilirubin level, Total Protein and Globulin, Creatinine and Urea level were also evaluated. Result showed that creatinine and urea, serum ALP, AST and ALT levels was significantly reduced (p < 0.05), while the levels of total Protein and Globulin increased significantly (p < 0.05) for the treated animals compared to the diabetic control group. In conclusion, the leaf essential oil of Citrus sinensis ameliorated the impaired renal and liver function; however, the time of harvest of the leaf does not significantly affect its ameliorative effect. Keywords—C.sinensis, Function indices, Harvest time, Leaf essential oil. I. INTRODUCTION ESEARCH into the medicinal uses of essential oil obtained from many plant sources have gained popularity recently and many of the essential oils have been shown to possess medicinal properties [1]-[3]. Correlation has been established in many cases between the medicinal potentials of these essential oils and their phenolic compounds. Essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. They are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove. Oil is O. Soji-omoniwa is with the Department of Biochemistry, Faculty of Natural and Applied Science, Plateau State University, Bokkos, Plateau State, Nigeria.(phone: +234 7034205898; e-mail: adejillian234@yahoo.com). N.O. Muhammad is with the department of Biochemistry and Molecular Biology, Federal University, Dutsin-Ma, Nigeria. (phone: +234 8033931900 e-mail: drmno02@gmail.com). L. A. Usman is with the Department of Biochemistry, University of Ilorin, Ilorin, Kwara State, Nigeria. (phone: +234 8035032378) B.P. Omoniwa is with the Department of Science Laboratory Technology, University of Jos, Jos, Nigeria. (phone:+2348037362620; e-mail: sojiomoniwa@gmail.com). "essential" in the sense that it carries a distinctive scent, or essence of the plant. Medical applications proposed by those who sell medicinal oils range from skin treatments to remedies for cancer, and often are based solely on historical accounts of use of essential oils for these purposes. Studies have shown that the yield of plant material, the essential oil content and quantitative composition of plants can be influenced by harvest time, ecological and climate conditions [4]. Essential oil is also affected by season as reported by [4]. They reported that the amount of essential oils and the concentrations of the phenolic constituents were the lowest in spring and the highest in June/July, the full blooming period. They determined that essential oil content were between 4.8-10.8% and major components were carvacrol (481.9-489.9 mg/mL), γ- terpinene (40.7-65.2 mg/mL), p-cymene (40.2-54.0 mg/mL) from June to July. Previous report showed that the highest essential oil content (2.33%) was at the full-flowering stages. This is due to high yields of fresh and dry biomass and content of oil at this stage [5]. Variation in the effect of harvesting hour on the essential oil content of Lemon balm grown in the Eastern Mediterranean was studied. The highest essential oil content (0.081%) was obtained at 6.00a.m when the plants were covered in dew. The study concluded that morning (6.00a.m) and evening (7p.m) harvests had yield advantage over noon (12p.m) harvest [6]. A similar pattern was also reported in a previous work [7]. They attributed the differences in the essential oil content to available moisture as well [7]. Another report however stated that there was no significant effect in harvest hour on composition and content of essential oil of Ocimum basilicum major components [8]. Leaf extracts of C. sinensis have been used in Nigerian local folk medicine to treat neurological disorders and to facilitate the digestion of food. It has also been used as an antidiabetic, antibacterial, antifungal, hypotensive, antioxidant, insect repellent, larvicidal, antiviral, uricosuric, anti-yeast, antihepatotoxic and antimutagenic agent [9]-[13]. In Odummara Obi-orodo, of Imo State, Nigeria, herbalists use concoction made from Citrus sinensis leaf, Magnifera indica, Carica papaya, Psidum guajava and other plants’ leaf to treat malaria [14]. The oils are generally in use in many foods, confectionery, drug, cosmetic, and flavoring products [9] and there have been claims on its use in managing several ailments in folk medicine and in some instances substantiated with scientific data. It is believed among some Nigerian Herbalists O. Soji-Omoniwa , N. O. Muhammad, L. A. Usman, B. P. Omoniwa Effect of Leaf Essential Oil of Citrus sinensis at Different Harvest Time on Some Liver and Kidney Function Indices of Diabetic Rats R World Academy of Science, Engineering and Technology International Journal of Bioengineering and Life Sciences Vol:8, No:5, 2014 487 International Scholarly and Scientific Research & Innovation 8(5) 2014 scholar.waset.org/1307-6892/9998274 International Science Index, Bioengineering and Life Sciences Vol:8, No:5, 2014 waset.org/Publication/9998274