Radioimmunoassay for the citrus bitter principle, naringin, and related flavonoid-7-O-neohesperidosides.

An immunoassay for the citrus bitter principle, naringin, and related flavonoid-7-O-neohesperidosides is reported. The assay detects ca. 2 ng of naringin and can be used to quantify this compound in the parts per billion (ppb) range in crude grapefruit juice and extracts of other plant tissues. The antiserum used is highly reactive with the 2-rhamnosyl-1-glucopyranose at the C-7 position but not with e.g. the isomeric 6-rhamnosyl-1-glucopyranose moiety and can, thus, be used to identify the stereochemistry of this disaccharide moiety at the C-7 position of flavanoids. The assay involves a directly iodinated naringin-[ (125)I] as immunotracer.