α-Mangostin, a naturally occurring xanthone, displays both fast-binding and slow-binding inhibitions to FAS in vitro. It inhibits FAS overall reaction with an IC50 value of 5.54 μM noncompetitively with respect to NADPH, and partially competitively against both substrates acetyl-CoA and malonyl-CoA. Its inhibitory activity is higher than classical FAS inhibitors such as C75, EGCG and curcumin. It induces apoptosis in breast cancer cells by inhibition of FAS. MW: 410.46. Purity ≥95% by HPLC