Foliar applied oil-in-water nanoemulsion formulated NK liquid nanofertilizer in the enhancement of antioxidant activities of leafy vegetable, Amaranthus tricolor L.

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The physicochemical properties of NK nanofertilizers (NFs) formulated with nanoemulsion in different surfactant systems and their impact on the antioxidant activities of the leafy vegetable, Amaranthus tricolor L. are studied. The formulated NK NFs incorporated with different nonionic surfactants Tergitol, Tween 80 and mixed surfactants are investigated. The nanoformulation characterizations including particle size, polydispersity index (PDI), zeta potential, surface tension and morphology are examined to verify the stability of nano-colloidal system in enhancing the NFs droplets for leaf absorption and resulting better in antioxidant activities shown by the vegetable. The particle sizes of formulated NFs are under 100 nm indicates the nanoemulsion incorporated in the formulation and the PDIs are below 0.4 indicating the NFs exhibit narrow size distribution with sufficient uniformity in the dispersion system. The zeta potential values are ranged from −13.17 to −5.47 mV while the surface tension values are ranged from 30.20 to 49.10 mN/m. The micrographs obtained from morphologies of nanoemulsion formulations indicate the evenly dispersed droplets in nanosized in different patterns. To evaluate the bioefficacy of the formulated NK NFs on the vegetable leaves, antioxidant tests are conducted including total chlorophyll content, total phenolic content and 2,2-diphenyl-1-picrylhydrazyl scavenging activity. The antioxidant results show the activities increases in the presence of nanoemulsion in comparison to the non-formulated sample and control thus highlighting that the NK NFs are efficient in delivering NK nutrients for improving their antioxidant activities as supported by the elemental analysis of encapsulation efficiency percentage (% EE) and NK concentration.