Phytochemical, antioxidant and toxicological properties of methanol extract of phyllanthus amarus

Thesis Abstract

The use of medicinal plants for the treatment of many diseases is associated with folk medicine from different parts of the World. However, information on the toxicology of these plants part used in Nigeria folk medicine is rare. Thus, this work is aimed at revealing a range of phytochemicals in the Phyllanthus amarus plant, the antioxidant constituents and its toxicologic effects on some important biochemical parameters in male albino rats. The potent bioactive agents in the leaves of Phyllanthus amarus plant were extracted and the antioxidant and toxicological potentials for in vitro analyses of the crude plant extract were evaluated using in vitro methods and male white albino rats as the model. The results showed that methanol extract scavenged 1,1- diphenyl-2- picryhydrazyl radical (DPPH) in a concentration – dependent manner with a correlation coefficient (R2) of 0.989, indicating antioxidant activity with effective concentration that inhibits fifty percent of the radical (EC50) of 6.93µg/ml compared to ascorbic acid standard with EC50 of 4.69µg/ml. Superoxide radical scavenging activity was concentration dependent with an EC50 of 5.01µg/ml compared with ascorbic acid standard with EC50 of 4.49µg/ml. The crude extract also showed hydroxyl radical scavenging activity with an EC50 of 6.47µg/ml compared to α tocopherol standard with EC50 of 5.73µg/ml. The methanol extract, also scavengemd nitric oxide radical in a concentration – dependent manner with 600µg/ml being more potent than 600µg/ml of α – tocopherol standard. Comparison of the anti-radical power (ARP) of DPPH (0.144), superoxide radical (0.199) and hydroxyl radical (0.175) of the extract revealed that the ARP of the extract against superoxide radical was most efficacious. The antioxidant vitamin contents of the extract showed that vitamin C was significantly higher (p Ë‚ 0.05), 1.65mg/100g when compared to vitamin A (1.52mg/100g) and vitamin E (0.89mg/100. Acute toxicity test was conducted using mice and there was no death recorded in the mean lethal dose (LD50) investigation. The 100, 200 and 400 mg/kgbw fed to rats showed significantly higher activity of catalase (p Ë‚ 0.05) at week two and week four. The aspartate aminotransferase (AST) showed non- significantly lower activity (p > 0.05) in group 3 of week one and four, while group 3 of week two was significantly higher (p Ë‚ 0.05) in week four. The alanine aminotransferase (ALT) indicated a relatively lower activity of ALT from week one to three while there was relative elevation of ALT activity in the test group of week four. The serum alkaline phosphatase (ALP) was significantly lower (p > 0.05) in the test group when compared to the control group 1 in week one. At week two and three, there were higher activities of ALP in all groups, though non- significant while in week four, there was a non- significantly lower activity of the enzyme in all groups. The serum urea concentration showed a significantly higher (p Ë‚ 0.05) level in all groups except group four in week one. In week two and three, there was a significantly higher level (p Ë‚ 0.05) while week four exhibited a non-significant increase in serum urea concentration in all groups. The creatinine concentration indicated a significantly higher level (p Ë‚ 0.05) in groups 2, 3 and 4 in week one. At week two, there was a significantly lower level (p > 0.05) in group two and four. In week three, there was a significantly higher concentration (p Ë‚ 0.05) in group two and four, while in week four; there was a non- significant difference in the concentration of serum creatinine in all groups. The Packed cell volume (PCV) and haemoglobin count were significantly higher (p Ë‚ 0.05) in all groups in week one. In week two, there was no significant increase (p > 0.05) in group three. In week three, there was a significantly higher level of PCV and Hb respectively (p Ë‚ 0.05). Week four indicated a non- significant decrease in all groups. White blood cell count showed a significantly higher level in group 3 and 4 (p Ë‚ 0.05) except group two in week one. In week two and three, there was an increase in group three while others showed no significant difference. In week four, there was a non – significant decrease in all groups. Histological analysis showed some level of toxicity in 100, 200 and 400mg/kgbw at beyond 14 days of administration. These results seem to suggest rich phytochemical constituents, moderate antioxidant activity, relatively safe level at acute phase (within 14 days) and some level of toxicity in enzyme activity at the chronic phase (after the 14 days of administration).