Evaluation of in vitro toxicity of common phytochemicals included in weight loss supplements using 1H NMR spectroscopy

Herbal and dietary supplements (HDS) are popular among consumers seeking a “natural” approach for improving their health, however at present there is a lack of evidence to support the claims of efficacy and safety for most of these products. Herbal weight loss supplements (WLS) are a group of HDS that are frequently implicated in cases of toxicity; however, the causative substances often remain unknown due to the complex chemical nature of such supplements. This study aimed to analyse the in vitro safety (in human liver carcinoma (HepG2) cells and colon carcinoma (Caco-2) cells) of 12 active compounds commonly found in WLS, first with safety screening using the MTT cytotoxicity assay, followed by metabolic profiling with 1H NMR spectroscopy. Of the phytochemicals evaluated, epigallocatechin-3,0-gallate (EGCG) was the only compound that caused a significant reduction in viability of both cell lines (25.3% in HepG2 cells and 18.5% in Caco-2 cells), and this decrease was potentiated by CYP450 induction with rifampicin. Subsequent 1H NMR analysis showed changes in key metabolites such as amines, amino acids, carboxylic acids, and glucose that were indicative of protein degradation and disrupted energy and lipid metabolism. Whilst the remaining 11 active compounds analysed did not demonstrate significant toxicity in isolation, these require further assessment to determine their safety when used in combination with other phytochemicals. Given that the majority of WLS contain multiple herbal ingredients, each with a complex chemical composition, it is important to understand the role of interactions in adverse events.