Structural features of endogenous polyphenols in modulating oxidative stability of tiger nut (Cyperus esculentus L.) oil: Insights from Rancimat and density functional theory

Profiled free polyphenols in tiger nut oil (TNO). • Quercetin/catechin/eriodictyol enhanced the oxidative stability of stripped TNO. • Quercetin/catechin/eriodictyol possessed excellent radical scavenging activity • The structure-activity relationship of key polyphenols in TNO was represented. • Hydroxyl number/position and C-ring structure regulate polyphenol activity. Tiger nut oil (TNO) is a promising edible oil with remarkable oxidative stability. This study aimed to elucidate the structure-activity features of endogenous free polyphenols in TNO associated with its oxidative stability. UPLC-ESI-Q TRAP-MS/MS analysis revealed 36 flavonoids, 14 phenolic acids, and 4 lignans in TNO. The major polyphenols covering the main skeletons were then added to stripped tiger nut oil (STNO) without any antioxidants. A combination of multi-method, including Rancimat assay and quantum chemical computations based on density functional theory was employed. Notably, quercetin, catechin, and eriodictyol showed the strongest antioxidant effect. The bond dissociation energy (75.69–100.89 kcal/mol) of the test polyphenol is significantly lower than its ionization potential and proton affinity. These differences were related to the structural characteristics of the polyphenols. This work improves our understanding of the key role of free polyphenols in the oxidative stability of TNO. Download: Download high-res image (216KB) Download: Download full-size image