The antioxidant activity of cerium oxide nanoparticles (CNPs) depends on the concentration of oxygen vacancies and Ce 3+ active sites. In the present work, we report the impact of 5 mol % trivalent rare-earth-doped (RE 3+ = Eu 3+ , Nd 3+ , Pr 3+ , and La 3+ ) CNPs on the oxidation state modulation and antioxidant property with respect to ionic radii. An increase in the lattice parameter, strain, and oxygen vacancy concentration was observed as a function of ionic radii. Among the various dopants in CNPs, La 3+ with higher ionic radii having smaller crystallite size (7.9 nm) and higher vacancy displayed better peroxidase, oxidase, and hydroxyl radical (HO • ) scavenging activities. The kinetic parameters for the peroxidase and oxidase activities were found to be superior with K m = 0.217 and 0.261 mM, respectively, for 5 mol % La 3+ -doped CNPs. To divulge the role of dopant concentration on the structural properties, we also explored using 10 and 20 mol % La 3+ doping in CNPs. Because of the smaller crystallite size (6.7 nm) and higher defect level (3.12 × 10 21 cm −3 ), 20% La 3+ doping showed superior peroxidase and oxidase activities, as shown by the low K m values. CNPs exhibit both peroxidase and oxidase activities in a concentration-dependent manner. Moreover, CNPs exhibit concentration-dependent peroxidase and oxidase activities that can be selectively activated for various theranostic applications. Thus, our results demonstrate the crucial role of ionic radii and the concentration of RE 3+ dopants on defect formation in CNPs for improved antioxidant properties of ceria.

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In this research work to evaluate in vitro antioxidant activity and HPTLC finger printing analysis of Physalis peruviana fruits. The chemical fingerprinting was carried out by high performance thin layer chromatography.  It was carried out by the CAMAG HPTLC system equipped with Linomat V sample applicator, twin through plate development chamber, TLC scanner III and integration software WIN CATS-4.02. Physalis peruviana fruit extract was tested for phytochemical screening and in vitro anti-oxidant enzymes like 2, 2-diphenyl-1-picryl hydrazyl radical (DPPH), total antioxidant activity and reducing ability. Physalis peruviana fruit extract effectively scavenged free radicals at all different concentrations and showed its potent antioxidant activity. Phytochemical analysis revealed the presence of various major phytoconstituents like alkaloids, flavonoids, saponins, phenolics, tannins and anthraquinones. The HPTLC fingerprint qualitatively revealed predominant amount of quercetin. Physalis peruviana fruit extract will be subjected to further extensive studies to isolate and identify their active constituents which are useful for understanding their mechanism of action as antioxidants.