Submitted to: Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/26/2010
Publication Date: 10/25/2010
Citation: Chung, S., Champagne, E.T. 2010. Ferulic acid enhances IgE binding to peanut allergens in western blots. Food Chemistry. 124:1639-1642. Interpretive Summary: Phenolic compounds are types of antioxidants commonly found in fruits and vegetables. They have received much attention because they have been shown to protect against cancer and provide other health benefits. Because of these properties, phenolic compounds have been used or added to foods as dietary supplements. Foods supplemented with phenolics have a higher level of phenolic compounds than foods without supplementation. Whether this unusual high level of phenolics has an adverse effect on immunoassays; such as, enzyme-linked immunosorbent assays (ELISA), and Western blots for peanut allergens, is not known. In this study, we postulated that phenolics at high levels would affect protein detection by Western blots and ELISA assays. To verify this, three simple phenolic compounds (ferulic, caffeic, and chlorogenic acids) commonly found in foods were tested. Each compound was mixed with a pooled plasma (containing IgE antibodies) from peanut-allergic individuals in Western blots and ELISA. Results showed that phenolics (ferulic acid in particular) enhanced the sensitivity of blot assays, but interfered with the ELISA assays. The implication of this is that underestimation of the levels of peanut allergens is possible if ELISA is used as a screening tool for peanut allergens in foods that contain high levels of phenolic compounds (e.g., foods supplemented with phenolics), and that overestimation of the allergenic capacity of peanut allergens could occur when analysis is done by Western blot.
Technical Abstract: Phenolic compounds at high concentrations are known to form insoluble complexes with proteins. We hypothesized that this complex formation could interfere with Western blot and ELISA assays for peanut allergens. To verify this, three simple phenolic compounds (ferulic, caffeic, and chlorogenic acids) commonly found in foods were tested. Each compound, at various concentrations, was mixed with a pooled plasma (containing IgE antibodies) from peanut-allergic individuals before incubation with a membrane in blots, or a microtiter plate in ELISA, both coated with peanut proteins/allergens. Results showed that of the three phenolics, ferulic acid interferred the most. When mixed with the plasma, ferulic acid (10 mg/mL) gave darker bands in Western blots, suggesting that it enhanced IgE binding; however, in ELISA, ferulic acid (> 0.1 mg/mL) reduced IgE binding. It was concluded that phenolics enhanced the sensitivity of blot assays, but interfered with the ELISA at the concentrations indicated. The implication of the findings is that underestimation of the level of peanut allergens is possible when foods with high amounts of phenolics are screened with ELISA for peanut traces, and overestimation of the allergenic capacity of peanut allergens could occur when analysis is done by Western blot.