*Article* **Antioxidant Activity of Bioactive Peptide Fractions from Germinated Soybeans Conjugated to Fe3O<sup>4</sup> Nanoparticles by the Ugi Multicomponent Reaction**

**Yarelys Elena Augusto-Jimenez 1,\*, Marcela González-Montoya <sup>2</sup> , Dany Naranjo-Feliciano <sup>3</sup> , Daniel Uribe-Ramírez <sup>2</sup> , Eliseo Cristiani-Urbina <sup>2</sup> , Carlos Díaz-Águila <sup>4</sup> , Hernani Yee-Madeira <sup>1</sup> and Rosalva Mora-Escobedo 2,\***


**Citation:** Augusto-Jimenez, Y.E.; González-Montoya, M.; Naranjo-Feliciano, D.; Uribe-Ramírez, D.; Cristiani-Urbina, E.; Díaz-Águila, C.; Yee-Madeira, H.; Mora-Escobedo, R. Antioxidant Activity of Bioactive Peptide Fractions from Germinated Soybeans Conjugated to Fe3O<sup>4</sup> Nanoparticles by the Ugi Multicomponent Reaction. *Molecules* **2021**, *26*, 5726. https://doi.org/ 10.3390/molecules26195726

Academic Editors: Višnja Stepani´c and Marta Kuˇcerová-Chlupáˇcová

Received: 22 July 2021 Accepted: 13 September 2021 Published: 22 September 2021

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**Abstract:** The conjugation of biomolecules to magnetic nanoparticles has emerged as promising approach in biomedicine as the treatment of several diseases, such as cancer. In this study, conjugation of bioactive peptide fractions from germinated soybeans to magnetite nanoparticles was achieved. Different fractions of germinated soybean peptides (>10 kDa and 5–10 kDa) were for the first time conjugated to previously coated magnetite nanoparticles (with 3-aminopropyltriethoxysilane (APTES) and sodium citrate) by the Ugi four-component reaction. The crystallinity of the nanoparticles was corroborated by X-ray diffraction, while the particle size was determined by scanning transmission electron microscopy. The analyses were carried out using infrared and ultraviolet–visible spectroscopy, dynamic light scattering, and thermogravimetry, which confirmed the coating and functionalization of the magnetite nanoparticles and conjugation of different peptide fractions on their surfaces. The antioxidant activity of the conjugates was determined by the reducing power and hydroxyl radical scavenging activity. The nanoparticles synthesized represent promising materials, as they have found applications in bionanotechnology for enhanced treatment of diseases, such as cancer, due to a higher antioxidant capacity than that of fractions without conjugation. The highest antioxidant capacity was observed for a >10 kDa peptide fraction conjugated to the magnetite nanoparticles coated with APTES.

**Keywords:** soybean; peptides; antioxidant capacity; magnetite nanoparticles; conjugation; multicomponent reaction
