PHYTOCHEMICALS, ANTIOXIDANTS AND TOXICOLOGICAL PROPERTIES OF METHANOL EXTRACT OF SECURIDACA LONGEPEDUNCULATA
ABSTRACT
One of the problems associated with medicinal plants in Nigeria is paucity of information on the phytochemistry and toxicity of some of these plants. The study aimed at revealing a range of phytochemicals in the plant, which are physiologically potent in ameliorating several diseases. The potent secondary metabolites in the leaves of this plant Securidaca longepedunculata , were extracted and their antioxidant and toxicological potentials were evaluated using in vitro methods and albino rats as the models. The results showed that methanol extract scavenged 1, 1- diphenyl-2- picrylhydrazyl radical (DPPH.) in a concentration dependent manner with a correlation coefficient (R2) of 0.976, indicating antioxidant activity with effective concentration that inhibits 50 percent of the radicals (EC50) of 90.02±0.2 µg/ml compared to ascorbic acid standard with EC50 of 98.01±0.2 µg/ml. Superoxide radical scavenging activity was concentration dependent with an EC50 of 350.11±0.42 µg/ml compared with ascorbic acid standard with EC50 of 812.97±0.97 µg/ml. The extract, also showed hydroxyl radical scavenging activity with an EC50 of 83.74±0.02µg/ml compared to α- tocopherol standard with EC50 of 54.16±0.01 µg/ml. There was an inverse correlation between the percentage inhibition and concentration with R2 of -0.958. The methanol extract, also scavenged nitric oxide radical in a concentration dependent manner with 500 µg/ml being more effective than 500 µg/ml of ascorbic acid standard. Comparison of the anti-radical power (ARP) of DPPH. (0.011), superoxide radical (0.003) and hydroxyl radical (0.012) of the extract revealed that the ARP of the extract against hydroxyl radical was most efficacious. The antioxidant vitamin contents of the extract showed that vitamin C was significantly high (p< 0.05), (4.62±0.14 mg/100g) when compared to vitamin A (0.902±0.05 µg/g) and vitamin E (1.474±0.01 mg/100g). The 100, 200 and 500 mg/kg bw fed to rats significantly increased (p< 0.05) catalase activity, while in weeks two and three the catalase activity decreased significantly (p< 0.05). The extract solution showed a maximum absorption at wavelength (lambdamax) of 285nm-thus indicating that subsequent investigations using the extract would be better at UV region in absorption spectra. There was no death in the mean lethal dose (LD50) investigation. The aspartate aminotransferase (AST) showed a significant decrease (p< 0.05) in week one and an increase in other weeks. Trhe alanine aminotransferase (ALT) showed a significant decrease (p< 0.05), in weeks one, three and four while week two showed a non-significant increase (p> 0.05). The serum alkaline phosphatase (ALP) showed a significant (P £ 0.05) decrease in activity in all the groups at weeks one and two. At week three only group two showed a non significant increase (P ³ 0.05); others showed a non significant decrease (P ³ 0.05). At week four, all the groups showed an increase, but only groups two and three were significant (P £ 0.05) when compared to their controls group 1. Both conjugated and unconjugated bilirubin of groups two to four of weeks two to four showed generally a significant increase (p< 0.05), compared with that of the control. The serum sodium level showed a significant increase (p< 0.05), in groups two and three of week one. Weeks two to three showed a non-significant increase (p> 0.05) compared to that of the control group. Serum potassium and chloride ion concentrations showed a significant decrease (p< 0.05) in weeks one to three and significant increase (p< 0.05) in week four. The serum urea showed overall significant decrease (p< 0.05) compared to that of the control group (p< 0.05). The serum creatinine showed a significant increase (p< 0.05) in weeks one and two, a non-significant decrease (p> 0.05) in week three and a significant decrease in week four (p< 0.05). Weeks one and two rats showed significant decrease (p< 0.05) in random blood sugar (RBS), while in weeks three and four, the rats showed significant increase (p< 0.05) in RBS concentration. The packed cell volume (PCV) and haemoglobin concentration (Hb) showed significant decrease (p< 0.05) when compared with those of the control group. The white blood cell (WBC) counts of the rats showed significant increase (p< 0.05). Histological analysis showed some level of toxicity in 100, 200 and 500 mg/kg b.w. at chronic stage (beyond 14 days of administration). These results seemed to suggest a rich phytochemical constituents, suggested a moderate antioxidant activity, a relatively safe level at acute phase (within 14 days) and a visible damage (moderate toxicity) at chronic stage.