Development and evaluation of a broad-specific immunochromatographic assay for screening of both tadalafil and its analogues in functional foods

Abstract

Illegal additives of tadalafil and related analogues in functional foods threaten public health. To generate broad-specific antibodies against both tadalafil and its analogues, tadalafil was activated through an oximation reaction for synthesis of conjugates, leaving the common structure of tadalafil analogues exposed as a major antigenic site. The desired antisera showed satisfied specificities to tadalafil and its major analogues with immunochromatographic (IC50) values ranging from 16.1 to 29.5 ng mL−1 in a referring indirect competitive enzyme-linked immunosorbent assay. The optimized IC assay showed detection thresholds ranging in 10∼20 μg g–1 for tadalafil and major analogues when detected fortified herbal samples in a dilution ratio of 1:103. Sixty herbal food supplements were screened and five were found to be positive using IC strip. It was confirmed by UPLC-PDA-MS/MS that positive samples contain target illegal additives in levels of 10∼20 mg g−1 (1%∼2%). In this range of containing percentage, sensitivity of the IC strip is adequate to screen tadalafil and its potential analogues in herbal products.