Comparative Studies of Antioxidant and Toxiological Properties of Methanol Extracts of Uvaria Chamae Leaves and Roots

Abstract

The efficacy of Uvaria chamae plant species in herbal remedies may have come as a result of trial and error. This could be as a result of poor information on the phytochemistry, antioxidant and toxicity of this plant parts. The present study compares the in vitro and in vivo antioxidant potentials and toxicities of methanol extracts of Uvaria chamae leaves and roots. Results of in vitro antioxidant potentials revealed that the methanol extract of Uvaria chamae leaves contains vitamin A (4871±79.21 I.U) and vitamin C (1.72±0.02%) while the root extract contains vitamin A (673.28±0.00I.U) and vitamin C (1.66±0.01%). Both extracts had equal contents of vitamin E (8.83±0.04 mg/100g). The leaf extract scavenged 1,1- diphenyl-2-picrylhydrazyl radical (DPPH) in a concentration dependent manner with the correlation coefficient (R2) of 0.839 and effective concentration (EC50) of 31.19 µg/ml, while the root extract scavenged DPPH with R2, 0.778 and EC50 , 14.00 µg/ml. These results were compared to the EC50 of ascorbic acid standard (25.29 µg/ml). The leaf and root extracts scavenged superoxide radical in a concentration dependent manner with EC50 of 5.93 µg/ml and 719.45 µg/ml, respectively, compared to the EC50 of ascorbic standard (30.27 µg/ml). Both the leaf and root extracts scavenged hydroxyl radical in a concentration dependent manner with EC50 of 107.89 µg/ml and 912.01 µg/ml, respectively, compared to the EC50 of vitamin E standard (106.66µg/ml). The result of the study revealed that the 1000 µg/ml root extract scavenged nitric oxide radical more than the leaf extract and vitamin E standard at the same concentration. At 500 µg/ml, the leaf extract was more effective at scavenging nitric oxide radical compared to the root extract and vitamin E standard. The leaf extract showed significantly higher (p<0.05) anti radical power (ARP) of superoxide (0.17) compared to the root extract (0.0014). However, the root extract showed significantly higher (p<0.05) ARP of DPPH (0.071) compared to the leaf extract (0.032). For the in vivo study, adult albino rats were divided into two sets (leaf and root extracts) of four groups each. Each group contained 8 rats. Comparative in vivo effects of the leaf and root extracts were determined by investigating the following parameters: catalase activity, liver marker enzymes (alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alanine phosphatase (ALP), serum urea, serum creatinine, serum electrolytes (Na+, K+, and Cl-) and some haematological parameters - haemoglobin (Hb), packed cell volume (PCV) and white blood cell (WBC) count. Because the median lethal dose (LD50) investigation revealed one death at the dose of 5000 mg/kg b.w for the root extract and none for the leaf extract, both extracts were orally administered at 100, 200 and 400 mg/kg b.w. In each set (i.e leaf and root extracts), group 1 received normal saline and served as the control while groups 2, 3, and 4 received 100, 200 and 400 mg/kg b.w doses of the extracts, respectively. At day 7 post treatment, ALP, Cl- ,K+, urea, creatinine , AST and WBC count were significantly higher (p< 0.05) in both sets of treatment groups compared to the control. Serum Na+, Hb and PCV were significantly lower (p< 0.05) in the treatment groups compared to the control. While the leaf extract showed significantly higher (p< 0.05) ALT activity, the root extract showed no significant difference (p>0.05). At day 14, both extracts had significantly higher (p< 0.05) catalase activity, urea, creatinine, Cl-, Na+ and WBC count. While, the leaf extract had significantly higher (p< 0.05) ALT and K+, the root extract had significantly higher (p< 0.05) AST activity when compared to the control. At day 21, the root extract showed significantly higher (p< 0.05) ALT, AST, catalase , Cl- and Hb while the groups were not significantly (p>0.05) affected by the leaf extract when compared to the control . However, at day 28, both extracts showed significantly higher (p>0.05) ALT activity. While the root extract showed significantly higher (p< 0.05) Na+ and ALP activity, the leaf extract showed none for them when compared to the control. Histological analysis showed some levels of toxicity at doses of 100, 200 and 400 mg/kg b. w at chronic stage (beyond 14 days of extracts’ administration). These results suggest that fluctuations at the initial period were as a result of the homeostatic processes in attempt for the organism to maintain normal body functioning at the end of the 28- day administrations of both extracts. Although the leaf extract was more efficacious in maintaining the normal body metabolism; the moderate toxicity exhibited by the extracts from LD50, ALT, AST and histopathological tests could compromise its efficacy in chronic phase of treatment.