[1] Univ Malaya, Dept Chem, Kuala Lumpur 50603, Malaysia
[2] CNRS, Inst Chim Subst Nat, F-91198 Gif Sur Yvette, France
[3] Univ Kebangsaan Malaysia, Fac Sci & Technol, Sch Chem Sci & Food Technol, Bangi 43600, Malaysia
[4] Inst Med Res, Herbal Med Res Ctr, Inst Med Res, Kuala Lumpur 50588, Malaysia