1. Department of Chemical and Physical Sciences, Walter Sisulu University, Private Bag X1 , Mthatha, Eastern Cape 5117, South Africa
2. Department of Chemical, University of Fort Hare, Alice, Eastern Cape 5700, South Africa
3. Department of Human Biology, Walter Sisulu University, Private Bag X1, Mthatha 5117, South Africa
4. Department of Chemical and Physical Sciences, Walter Sisulu University, Private Bag X1, Mthatha 5117, South Africa