Can oligomeric proanthocyanidins interfere with UHPLC analysis of spermidine in nutritional supplements?

•Nutritional supplement containing spermidine and OPC caused analytical phenomenon.•Interestingly, spermidine was partly undetectable in the presence of OPC.•Interfering impact of OPC on the quantification of spermidine and other polyamines.•OPC have a high binding affinity for (pure) spermidine and spermine.•Different spermidine-containing raw materials (wheat, barley, algae) investigated. The impact of oligomeric proanthocyanidins (OPC) on UHPLC analysis of spermidine was investigated because spermidine could not be detected in a commercial nutritional supplement containing both health-enhancing compounds. Therefore, pure spermidine and other raw materials rich in spermidine (wheat germs, barley, algae) were mixed with OPC-containing extracts. Results obtained showed that mixing pure solutions of spermidine with OPC extracts led to a fast and significant reduction in spermidine determined, while mixing other raw materials with OPC extracts resulted in a much slower reduction to a lesser extent. Dwell time hardly influenced the amount of residual spermidine found, while different food matrices might reduce the extent of binding by OPC. Other relevant analytes in polyamine biosynthesis (arginine, ornithine, putrescine and spermine) were also investigated showing only a slight decrease for amino acids and putrescine, whereas especially spermidine and spermine have a higher affinity to be bound by OPC. Thus, the spermidine analysis of OPC-rich food supplements may give dramatically lower levels or even lead to false-negative results.