Recently, six furanocoumarin derivatives isolated from grapefruit juice were found to be inhibitors of CYP3A4, suggesting that they may be clinically active and useful constituents. We succeeded in developing a sensitive and specific enzyme-linked immunosorbent assay (ELISA) for these furanocoumarin derivatives in grapefruit juice.
In this study, we examined the correlation between immunoactivity as indicated by ELISA and CYP3A4 inhibitory effects, in order to determine whether ELISA is a useful method for analysis of the CYP3A4-inhibitory activity of furanocoumarin derivatives. Our results show a close correlation between the values. Therefore, our findings strongly indicate that ELISA is a useful method for analysis of these furanocoumarins.
Using this ELISA, grapefruit-derived products (grapefruit juice, jam and marmalade) were examined for furanocoumarin derivatives. Immunoactivity analysis was used to determine the amount of 6',7'-dihydroxybergamottin conversion. The amount of 6',7'-dihydroxybergamottin conversion was 13.0 μg/g with grapefruit juice, 40.0 μg/g with grapefruit marmalade and 1.7 μg/g with grapefruit jam. In addition, it was found that the heat treatment of grapefruit juice decreases the immunoactivity as indicated by ELISA and the CYP3A4-inhibitory activity. Moreover, the decreasing rate of the CYP3A4-inhibitory activity was lower than that of the immunoactivity as indicated by ELISA. Therefore, when the heat-treating grapefruit-derived products were analyzed by the ELISA, it was suggested that the CYP3A4-inhibitory activity might be estimated low. These findings will become indexes of the drug interaction of grapefruit-derived products.
