1. Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Hatfield 0028, South Africa
2. Department of Anatomy, University of Pretoria, Pretoria 0007, South Africa
3. Department of Chemistry, University of Pretoria, Hatfield 0028, South Africa
4. Department of Biochemistry and Microbiology, University of Zululand, KwaDlangezwa 3886, South Africa