Citation: Al-Saif, A.M.; Elnaggar, I.A.; Abd El-wahed, A.E.-w.N.; Taha, I.M.; Abdel-Aziz, H.F.; Farouk, M.H.; Hamdy, A.E. Improvement of Fruit Quality and Phytochemical Components of Pomegranate by Spraying with B 2 O 3 and ZnO Nanoparticles. Agronomy 2023, 13, 2305. https://doi.org/10.3390/ agronomy13092305 Academic Editor: Luis Noguera-Artiaga Received: 31 July 2023 Revised: 25 August 2023 Accepted: 30 August 2023 Published: 31 August 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). agronomy Article Improvement of Fruit Quality and Phytochemical Components of Pomegranate by Spraying with B 2 O 3 and ZnO Nanoparticles Adel M. Al-Saif 1 , Ibrahim A. Elnaggar 2 , Abd El-wahed N. Abd El-wahed 2 , Ibrahim M. Taha 3 , Hosny F. Abdel-Aziz 2 , Mohammed H. Farouk 4 and Ashraf E. Hamdy 2, * 1 Department of Plant Production, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia; adelsaif@ksu.edu.sa 2 Department of Horticulture, Faculty of Agriculture, Al-Azhar University, Cairo 11651, Egypt; ibrahimelnagar5@azhar.edu.eg (I.A.E.); abdelwahedabdelwahed485.el@azhar.edu.eg (A.E.-w.N.A.E.-w.); hosny_fathy86@azhar.edu.eg (H.F.A.-A.) 3 Department of Food Science and Technology, Faculty of Agriculture, Al-Azhar University, Cairo 11884, Egypt; ibrahimtaha164@azhar.edu.eg 4 Key Laboratory of Product Quality and Security, Jilin Agricultural University, Ministry of Education, Changchun 130117, China; mhfarouk@jlau.edu.cn * Correspondence: ashrafezat@azhar.edu.eg Abstract: Pomegranate is one of the most important and widely distributed trees. Boron and zinc are important nutrients for plant growth and fruit quality. Nanotechnology has emerged as one of the most innovative scientific fields in agriculture. This study was conducted to describe the changes in the physiochemical characteristics (weight, diameter, length, firmness and color), as well as the phytochemicals attributes (total phenolics, total flavonoids, ascorbic acid, anthocyanin and antioxidant %) and minerals contents, of pomegranates fruits of the ‘Wonderful’ cultivar as a result of spraying pomegranate trees using nanomaterials (zinc oxide (ZnONPs) and boron oxide (B 2 O 3 NPs)). In three successive developmental stages (full bloom, 6 weeks after full bloom and one month before harvest time), the trees were sprayed with 0.25, 0.5 and 1 g/L ZnONPs, as well as 0.25, 0.5 and 1 g/L B 2 O 3 NPs during the 2021 and 2022 seasons. The application of ZnONPs and B 2 O 3 NPs influenced the qualitative characteristics of the fruits in the studied seasons. The highest marketable % was observed for the 0.50 and 1 g/L ZnONPs and 1 g/L B 2 O 3 NPs compared to the other treatments. Also, a positive effect was recorded for the ZnONPs and B 2 O 3 NPs on the fruits’ physical properties. All of the ZnONP and B 2 O 3 NP treatments resulted in increasing the total phenolic, flavonoid, anthocyanin and ascorbic acid contents and the antioxidant activity in the pomegranate juices. In conclusion, our results suggest that spraying pomegranate trees with ZnONPs and B 2 O 3 NPs improves the marketable fruit, enhances the fruit quality and increases the bioactive components and antioxidant activity. Keywords: nanotechnology; marketable fruits; firmness; anthocyanin; ascorbic content; bioactive compounds 1. Introduction Pomegranate (Punica granatum L.) is a member of the family Punicaceae, and it is culti- vated in subtropical and tropical regions [1]. Although there are more than 500 variations, juice manufacturing currently uses the cultivar ‘Wonderful’ [2], which arose as a crop in Florida and then spread to the state of California in 1896. The tree is strong and productive, while the fruit is round and flat in the poles, large in size, and dark in color, with a medium thick shell, and it has a deep juicy red pulp [3]. According to statistics, the total area cultivated with pomegranates in Egypt is 80,109 feddan [4]. The chemical composition of pomegranate fruit and juice is affected by the genetic and geographical origin, climatic conditions, maturity stage, agricultural practices, microbial load and the method of juice extraction [5]. Agronomy 2023, 13, 2305. https://doi.org/10.3390/agronomy13092305 https://www.mdpi.com/journal/agronomy