Presence of higenamine in beetroot containing 'foodstuffs' and the implication for WADA-relevant anti-doping testing

Higenamine is an alkaloid found within plant species including some that are used in traditional Asian and Chinese herbal medicines. Identified as having mixed mode adrenergic receptor activity, higenamine is present within some nutritional supplements marketed for stimulant and/or weight loss. Its inclusion within nutritional supplements can be via its natural presence within botanical ingredients or as a synthetic additive, often added in mg amounts. The World Anti-doping Agency (WADA) prohibited list has contained higenamine since 2017 as banned at all times in the beta-2 agonist (S3) category, with a reporting level of 10 ng/ml for the free parent form in urine. In this study, an investigation into the content of beetroot or beetroot-containing foodstuffs and supplement products was conducted. Higenamine was confirmed as present within the majority of foodstuffs and supplements, with experimental evidence that higenamine can arise within beetroot extracts through heating. The results in this paper demonstrate the first reported evidence of a link between beetroot and this WADA prohibited substance. To investigate the link between intake and excretion, concentrated beetroot drinks were consumed by six individuals and higenamine quantified in their urine. Free higenamine was detected in the urine of all individuals, with maximum measured concentration in samples of less than 1% of the current WADA reporting limit. Although the risk of an inadvertent doping violation by consumption of the foodstuffs and products investigated in this study is low, beetroot as a source of higenamine should be considered by athletes.