1. Natural Products Research Group, Dept. of Chemistry, University of Surrey, UK, Guildford, United Kingdom
2. Pen Resource University, Gombe, Nigeria
3. Department of Chemical Sciences, Federal University of Kashere, Gombe, Nigeria
4. Royal Botanic Gardens, Kew, Kew, UK
5. Dept of Chem., Univ. of Dar es Salaam, Dar es Salaam, Tanzania
6. Dept de Chimie Industry, Univ. de Kinshasa, DR Congo