1. Department of Chemistry, University of Ilorin, Nigeria
2. Department of Chemistry, University of York, York, UK
3. Phytomedicine and Phytopharmacology Research Group, Department of Plant Sciences, University of the Free State, QwaQwa Campus. Private Bag X13, Phuthaditjhaba, South Africa
4. School of Chemistry and Physics, University of Kwazulu-Natal, Scottsville, Pietermaritzburg, South Africa