Effect of ultraviolet doses in combined ultraviolet-ultrasound treatments on trans-resveratrol and trans-piceid contents in sliced peanut kernels.

Peanuts are known to synthesize resveratrol, a stilbene phytoalexin, associated with cancer chemopreventive activity and cardioprotection. A modified HPLC method developed and validated to determine trans-resveratrol and trans-piceid concentrations in a single analysis run exhibited recoveries, precision, linearity, and limits of detection consistent with or better than those of methods previously reported in the literature. The effect of combined treatments, ultrasound (US) followed by varying UV light (UV) doses (three distances, three exposure times) on trans-resveratrol and trans-piceid concentrations in peanuts was determined. All nine US-UV treatments significantly increased trans-resveratrol contents from 0.03 microg/g, in untreated peanut control, to 2.10-4.73 microg/g and trans-piceid contents from 0.07 to 0.23-0.38 microg/g. Increases in trans-resveratrol were not influenced by UV distance and time. US and UV, individually, increased trans-resveratrol to 4.29 and 2.36 microg/g, respectively. The US and UV treatment combinations used did not exhibit synergistic effect compared to US treatments alone.