Molecule of the Month

October 2006: Lycopene

Lycopene is the molecule responsible for the red color of tomatoes and watermelon. It belongs to a class of pigment molecules known as carotenoids.

Its color results from chemical bonds that alternate between single and double, called conjugated double bonds (C=C–C=C–C=C). The double bonds in lycopene are trans (see structure). Heat processing can rearrange some of them to cis, or can even destroy the molecule altogether. As a result, processed tomato products lose some of their bright red color during preparation.

Lycopene is an antioxidant. It may help prevent cancer by combining with singlet oxygen, a suspected carcinogen.