Figure 1.

The structure of various natural products exerting chemopreventive effect. The structures of curcumin, tetrahydrocurcumin, xanthorrizol, ar-turmerone, and demethoxycurcumin were adapted from Itokawa et al.⁵ The structures of bruceine A and brusatol were adapted from Hall et al.⁶ The structure of thymoquinone was adapted from Bassha et al.⁷ The structures of panduratin A, pinostrobin, and pinocembrin were adapted from Kiat et al.⁸ The structures of brazilein and brazilin were adapted from Laksmiani et al.⁹