trans-Resveratrol Content in Commercial Peanuts and Peanut Products

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Abstract
A modified high-performance liquid chromatographic (HPLC) method for determination of trans-resveratrol (resveratrol) in peanuts and peanut products has been developed. Resveratrol was extracted with acetonitrile−water (90/10, v/v) by blending with diatomaceous earth at high speed followed by purification of an aliquot of the extract on a minicolumn packed with Al2O3−ODS (C18) mixture. The column was eluted with acetonitrile−water (90/10, v/v), eluate was evaporated under nitrogen, and residue was dissolved in HPLC mobile phase. Resveratrol in an aliquot of purified extract was quantitated by HPLC on silica gel with n-hexane−2−propanol−water−acetonitrile−acetic acid (1050/270/17/5/1, v/v) as a mobile phase. The recovery of resveratrol added to diatomaceous earth at 0.05 μg/g was 98.95 ± 17.79%; the recovery of the standard added to fresh peanuts (with 0.070 μg/g natural level of resveratrol) at 0.50, 5.00, and 10.00 μg/g was 117.23 ± 8.87, 100.10 ± 2.49, and 100.45 ± 1.51%, respectively. The quantitation limit of resveratrol in fresh peanuts was about 0.01 μg/g. Roasted peanuts had the lowest content of resveratrol of 0.055 ± 0.023 μg/g (n = 21), while in peanut butter its concentration was significantly higher, 0.324 ± 0.129 μg/g (n = 46), and boiled peanuts had the highest level of 5.138 ± 2.849 μg/g (n = 12). Resveratrol content in commercial peanut products was similar to the resveratrol content of the raw peanut fractions routinely used for making them. Keywords: trans-Resveratrol; resveratrol; Arachis hypogaea L.; peanuts; groundnuts; peanut maturity; roasted peanuts; peanut butter; boiled peanuts; commercial peanuts; peanut fractions; peanut brands; peanut shells; Florunner; HPLC analysis; phytoalexin