1. Centre for Natural Products and Drug Discovery; University of Malaya; Kuala Lumpur 50603 Malaysia
2. Pharmacy Discipline; Life Science School; Khulna University; Khulna 9208 Bangladesh
3. Department of Chemistry; Faculty of Science; University of Malaya; Kuala Lumpur 50603 Malaysia
4. Medicinal Chemistry and Natural Products Research Group; School of Pharmacy and Biomolecular Sciences; Faculty of Science; Liverpool John Moores University; James Parsons Building Byrom Street Liverpool L3 3AF UK