1. Catalysis and Peptide Research Unit, University of KwaZulu-Natal , Private Bag X54001,Durban 4000, South Africa
2. Department of Pharmaceutical Sciences, University of KwaZulu-Natal , Westville Campus, Durban, 4000, South Africa
3. Department of Chemistry, University of Zululand , Private Bag X1001, KwaDlangezwa 3886, South Africa
4. School of Physiology, Faculty of Health Sciences, University of the Witwatersrand , Johannesburg 2193, South Africa