1. Pharmacology Division, Rhodes University, Grahamstown 6140, South Africa
2. Department of Chemistry, Faculty of Science, Federal University, Otuoke Bayelsa 562103, Nigeria
3. School of Chemistry and Physics, College of Agriculture, Engineering Sciences, University of KwaZulu-Natal, Durban 4000, South Africa
4. Pharmaceutical Chemistry Division, Faculty of Pharmacy, Rhodes University, Makhanda 6140, South Africa
5. School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, Durban 4000, South Africa