Phenolic profile and antioxidant activity of free/bound phenolic compounds of sesame and properties of encapsulated nanoparticles in different wall materials

This study aimed to evaluate the antioxidant activity of free and bound flavonoid or phenolic compounds extracted from the sesame seed (Oltan and Yekta varieties) as natural antioxidants and to demonstrate the properties of nanoparticles. The total phenolic content (TPC) of Oltan was higher (864.70 mg GAE/100 g seed) than that of Yekta (629.23 mg GAE/100 g seed). Oltan took up higher amounts of free (516.86 mg GAE/100 g seed) and bound (347.83 mg GAE/100 g seed) phenolics than Yekta. Also, the Yekta variety exhibited lower amounts of free (45.89 mg CE/100 g seed) and bound flavonoids (21.51 mg CE/100 g seed) and the total flavonoid content (TFC) (67.40 mg CE/100 g seed). Chlorogenic acid was the major phenolic compound present in the sesame seed. In both the DPPH and ferric reducing antioxidant power (FRAP) assays, the highest antioxidant activity was observed in the Oltan variety. Free phenolics showed the highest antioxidant activity, followed by bound phenolics, free and bound flavonoids. Therefore, free phenolics of the Oltan variety were encapsulated in Portulaca oleracea and Trigonella foenum-graecum seed gums. All nanoparticles showed nanometric size from 236.1 to 680.7 nm, negative zeta potential from -35.4 to -18.3 mV, high encapsulation efficiency from 61.35% to 74.49%, and desirable polydispersity index (PDI) between 0.315 and 0.332. Higher release of phenolics and sedimentation rate were observed in phenolic compounds encapsulated in Khorfeh and Shanbalileh, respectively. The gradual release of phenolic compounds, as well as sedimentation rate of composite coating during 40 days of storage, demonstrated that nanoencapsulated phenolics of sesame within the composite gum coating could be used as natural antioxidants in food systems.