Figure 2. UV absorption curves for trans- and cis- isomers of resveratrol as recorded by the DAD of the HPLC instrument.

Both isomers absorb in the solar UV range between 290 nm and 400 nm, indicating the potential for destructive photochemical reactions. The trans- isomer absorbs UV with a broad peak between 304 nm and 321 nm and a molar extinction coefficient of about 30,000. The cis- isomer absorbs UV with a peak at 286 nm and a molar extinction coefficient of about 15,000.