Metabolite and Mineral Diversity in Onions Due to Genotype and Environment and Potential for Cancer Prevention.

In food crops, the type and abundance of bioactives is often influenced by genotype and environment (e.g. abiotic/biotic stress, soil mineral content), and therefore it is important to identify varieties and growing locations that provide enhanced benefits to human health. Allium species such as onion and garlic produce bioactive compounds that can protect against chronic diseases such as cancer. Here, we utilized a non-targeted metabolomics and ionomics workflow on onion bulbs using GC-, UPLC-, and ICP-MS. Nine onion varieties were grown at three locations. The analysis revealed that metabolite diversity was influenced by both variety and growing environment. Minerals that varied included calcium, cadmium, and selenium. In addition, a dietary study was performed to evaluate the effects on the development of breast cancer in a transgenic mouse model. The diets incorporated 30% w/w onion into a purified rodent diet mix. Anti-cancer screening assays and clonal expansion assays in the FVB-Tg(MMTV-PyMT) transgenic mouse model of breast cancer revealed that mice fed a diet supplemented with 30% w/w Vaquero (yellow onion, equal to 5% w/w of daily consumption in humans) showed significant inhibition of the growth of neoplastic breast pathologies compared to a diet supplemented with red onion (Redwing) or the control diet (SUMO32). Metabolomics analyses of the diets revealed significant phytochemical differences between the SUMO32 and SUMO32-onion, as well as red vs. yellow onion. In summary, mass spectrometry analysis of onion varieties revealed phytochemical diversity and identified candidate bioactive compounds with anti-cancer properties.