Antioxidant Activity of the Aqueous Crude Extract of Ocimum gratissimum LINN. Leaf on Basal and Cadmium-induced Serum Levels of Phosphatases in Male Guinea-pigs

The antioxidant activity of the aqueous crude extract of Ocimum gratissimum Linn. leaf on the basal and traumatized (cadmium-induced) serum levels of alkaline phosphatase (ALP), total acid phosphatase (ACPT) and prostatic acid phosphatase (ACPP) of the male guinea-pig (GP) were evaluated. Preliminary experimentation showed that the effects of the aqueous crude extract of O. gratissimum on basal serum phosphatases were slightly more in the oral than the intraperitoneal (i.p) route. Oral administration of 20mg of O. gratissimum caused a timedependent decrease in the basal serum levels of ACPT and ACPP without an effect on ALP values. The inhibitory effects compared to the control were maximum at 4 hours. Furthermore, O. gratissimum given orally, caused significant dose-dependent decreases (p<0.05) of the basal serum levels of ACPT and ACPP at p<0.05. Basal serum concentrations of ACPT and ACPP changed from 23.50±1.04 and 7.50±0.29 to 8.25±0.75 and 2.25±0.29 IU at 20mg, representing 65 and 70 % decreases respectively. In contrast, 0.25-8mg/kg of cadmium (Cd) given intraperitoneally, caused significant dose-dependent increases (p<0.05) in the phosphatase enzymes. However pretreatment with 5mg of the crude extract, which on its own had little effect on basal serum phosphatase levels, followed by i.p administration of Cd, caused a reversal of the Cd-induced dose-response curves on the various phosphatase levels to negative values. These results may be due to the oxidative and the antioxidative biochemical antagonistic properties of the agents used in these experiments. They may also be due to enzyme conformational changes and effects of eugenols and flavonoids in the crude extract of O. gratissimum. @ JASEM Oxidation is an essential process in all organisms which involves redox reactions. These reactions normally generate reactive oxygen species (ROS) or highly reactive free radicals that can react virtually with all cell components to cause tissue injury (Collier et al., 1992). Exogenous sources of free radicals include tobacco smoke, ionization radiation, certain pollutants such as cadmium, vanadium, crude oil, organic solvents and pesticides (Robinson et al., 1997). The resulting oxidative free radicals are obligate intermediates of many metabolic reactions but may also cause pathological damage (Floyd et al., 1990). Similarly, antioxidation is the reversal of the above described processes mediated through scavenging of the free radicals, by dismutase enzyme systems, and phenolic-rich compounds such as flavonoids (Sardesai 1995; Rice-Evans et al., 1996). The body has evolved a number of interrelated antioxidant mechanisms to maintain redox homeostasis (Toyokuni et al., 1999). These antioxidant mechanisms include antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), gluthathione peroxidase (GSH-Px), heme oygenase (HO) etc (Ames et al., 1993; Sardesai 1995; Sies, 1997; Vertuani et al., 2004). A disturbance in the balance between the production of reactive oxygen species or free radicals and antioxidant defense, which may lead to tissue injury, is termed ‘Oxidative Stress’. Ocimum gratissimum Linn. locally referred to as “Scent Leaf”, is a vegetable commonly used as a spice in its unprocessed form in most West African and Nigerian dishes because of its very intense and dominant flavour of cloves (Odukoya et al., 2005). It is also an antioxidant (Odukoya et al., 2005; Leal et al., 2006; Afolabi et al., 2007) with volatile oils which contain phenolic-eugenols, thymol, flavonoids, phenylpropanoids, linalool, citral etc as pharmacologically active agents (Jedlickova et al., 1992; Leal et al., 2006). These active agents confer on it its anti-oxidative, chemotherapeutic, antispasmodic and analgesic actions (Ilori et al., 1996; Nakamura et al., 1999; Aziba et al., 1999; Rabelo et al., 2003). Most of the studies/investigations carried out with O. gratissimum did not show a qualitative (dose-andtime-dependent) effect of the agent. Furthermore, none of the studies reveal whether this agent will inhibit both basal and traumatized levels of phosphatases in the body’s pathology. It is therefore in that light that we seek to answer these questions in this study, using cadmium to induce oxidative stress by stimulating serum phosphatase activities. MATERIALS AND METHODS MATERIALS Electrical centrifuge (Hamilton Bell Co Inc, Montvale NJ); analytical weighing balance, atomic mass spectrophotometer (Humalyzer Junor, Human GmBH); incubator (Phillip Harris Ltd, England); fresh O. gratissimum L. leaves; test tubes; dissecting sets, pipettes, oral canular; sterile injection needles and syringes; sterile specimen bottles. Chemicals: Absolute alcohol (BDH Chemicals Ltd, England); Urethane m.p 47C-50C (BDH Chemicals Ltd, England,); 40% formalin (M&B, England); Antioxidant Activity of the Aqueous Crude Extract of Ocimum gratissimum LINN. Leaf on Basal and Cadmium-induced ................ * Corresponding author: Aprioku, J.S. 34 Cadmium Chloride 99.5% (Chadwell Heath Essex, England); commercially available Alkaline Phosphatase test kit (QCA, S.A, Amposta / Spain); Acid Phosphatase test kit (Randox Lab Ltd, UK); distilled water (obtained from the Department of Chemistry, University of Port Harcourt, Nigeria); all other chemicals were of analar grades. Animals: Adult male guinea-pigs of average weight 450±5g were obtained from the animal house in the University of Port Harcourt, Nigeria and allowed to acclimatize for 14 days. The guinea-pigs were fed with fresh elephant grass daily ad libitum at a room temperature of 22C with 12-hr light/dark cycle.