(P01-003-25) An Emulsional Rollercoaster: Saponin Profile and Concentration Are Moderately Associated With Carotenoid Bioaccessibility From Spinach (Spinacia oleracea)

Objectives: Carotenoid content and bioaccessibility are definitively separate traits in spinach as well as many other crops. The disconnect between these traits is hypothesized to be due to chemical factors that comprise the food matrix. Spinach produces a unique array of triterpenoid saponins, termed “yossosides”, which are naturally occurring emulsifiers.

Given that carotenoid transport from the intestinal lumen into the body largely relies on emulsifier-containing mixed micelle formation, we hypothesized that saponins contribute to differential carotenoid bioaccessibility observed in spinach.

Methods: We assembled a genetically diverse population of 30 spinach accessions containing both commercial varieties and wild germplasm and cultivated this population under controlled conditions. Carotenoid bioaccessibility was determined using a three-stage in vitro digestion while carotenoids and saponins were quantified using UHPLC-PDA and UHPLC-MS/MS, respectively.

Results: Carotenoid bioaccessibility was poorly associated with initial content (R=0.13 and 0.25 for lutein and ß-carotene, respectively). Saponin content varied (3.65 – 14.68 mg/100g DW) and the absence of specific yossosides in some varieties indicates natural variation in structural or regulatory genes. Interestingly, yossoside concentration was negatively associated with lutein (R=-0.53) and ß-carotene (R=-0.46) suggesting competition for metabolic precursors. Despite the emulsifying properties of saponins, total yossosides were moderately positively associated with lutein (R=0.41) and ß-carotene (R=0.34) bioaccessibility.

Conclusions: These data indicate that other molecules in the spinach matrix are playing a more prominent role in determining carotenoid bioaccessibility. Future research will focus on elucidating these factors to create molecular targets for plant breeders developing nutritionally enhanced cultivars of spinach and potentially other fruits and vegetables.

Funding Sources: USDA 3092-10700-066-001-S