Antioxidant Activity and Cytotoxicity of the Leaf and Bark Extracts of Tarchonanthus camphorates 

Sarah K Nanyonga¹, Andy R Opoku², Francis B Lewu³, Opeoluwa O Oyedeji⁴, Moganavelli Singh⁵, Adebola O Oyedeji⁶*

¹Department of Chemistry, ²Department of Bio-Chemistry and Microbiology, University of Zululand, Private Bag X1001, KwaDlangewa, 3886, ³Department of Agriculture, Cape Peninsula University of Technology, Private Bag X8, Wellington, 7654, ⁴Department of Chemistry, University of Fort Hare, Private Bag X1314, Alice, 5700, ⁵Department of Biochemistry, University of KwaZulu-Natal, Westville Campus, Durban, 4000, ⁶Department of Chemistry and Chemical Technology, Walter Sisulu University, Private Bag X1, Mthatha, 5099, South Africa 

*For correspondence: Email: aoyedeji@wsu.ac.za  Tel: +27 47 502 1951, 76 426 0279 

Received:  11 May 2012                                                                            Revised accepted: 18 April 2013

Tropical Journal of Pharmaceutical Research, June 2013; 12(3): 377-383

Purpose: To investigate the antioxidant potential and cytotoxicity of the leaf and bark extracts of Tarchonanathus campharatus..

Methods: The antioxidant activity of the aqueous leaf extract (Aq LF), methanol leaf extract (MET LF), dichloromethane leaf extract (DCM LF), methanol bark extract (MET BK), dichloromethane bark extract (DCM BK),  and ethyl acetate bark extract (Et Ac BK) were examined by 1,1-Diphenyl-2-picryl-hydrazil (DPPH), 2’-azinobis-(3-ethylbenzothiazo­line-6-sulfonic acid) (ABTS^.+), nitric oxide radical scavenging, reducing power and iron chelating activity methods. Brine shrimp lethality and MTT cytotoxicity tests were used to investigate the cytotoxicity of the extracts.

Results: The Aq LF, DCM LF, MET LF and MET BK showed good DPPH, ABTS radical scavenging and total reducing power activities. Total reducing power was high and in the rank order of DCM LF > Aq LF > MET LF > MET BK. All the extracts, however, showed weak nitric oxide scavenging activity as well as weak iron chelating ability. Flavonoids, phenols, tannins and saponins were present in some of the extracts, but alkaloids, terpenoids, cardenolides and cardiac glycosides were absent in all the extracts. All the extracts did not show significant cytotoxic properties (p ≥ 0.05) with 50% inhibitory concentration IC₅₀ values > 30 µg/ml in both cytotoxicity assays.

Conclusion: The antioxidant activity and low cytotoxicity of Tarchonanthus camphoratus probably justify its use in folk medicine.