Anik Molla,1 Md Minhazul Hoque,1 Fahmida Tasnim Richi,2,3 M Humayan Kabir,1 Safaet Alam,2,4 Nazim Uddin Ahmed,5 Nazim Uddin Emon,6 Chuxiao Shao,7 Chunlai Zeng,8 Shuanghu Wang,7 Peiwu Geng,7 Abdullah Al Mamun7 

1Department of Glass and Ceramic Engineering, Rajshahi University of Engineering and Technology, Rajshahi, 6204, Bangladesh; 2Department of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Dhaka, Dhaka, 1000, Bangladesh; 3Department of Pharmacy, University of Asia Pacific, Dhaka, 1215, Bangladesh; 4Chemical Research Division, BCSIR Dhaka Laboratories, Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka, 1205, Bangladesh; 5Drugs and Toxins Research Division, Bangladesh Council of Scientific and Industrial Research, Rajshahi, Bangladesh; 6Department of Pharmacy, Faculty of Science and Engineering, International Islamic University Chittagong, Chittagong, 4318, Bangladesh; 7Central Laboratory of The Lishui Hospital of Wenzhou Medical University, The First Affiliated Hospital of Lishui University, Lishui People’s Hospital, Lishui, Zhejiang, 323000, People’s Republic of China; 8Department of Cardiology, Central Laboratory of The Lishui Hospital of Wenzhou Medical University, The First Affiliated Hospital of Lishui University, Lishui People’s Hospital, Lishui, Zhejiang, 323000, People’s Republic of China

Correspondence: Abdullah Al Mamun, Central Laboratory of The Lishui Hospital of Wenzhou Medical University, The First Affiliated Hospital of Lishui University, Lishui People’s Hospital, Lishui, Zhejiang, 323000, People’s Republic of China, Tel +86-19715780050, Email pharmaalmamun@yahoo.com

Introduction: ZnO nanoparticles (NPs) have garnered significant attention due to their remarkable multifunctionality, particularly in biomedical and environmental applications.
Methods: The study synthesized ZnO NPs using Citrus reticulata Blanco peel extracts. The structural, morphological, and optical properties of ZnO NPs have been analyzed. The antibacterial and antioxidant activity of ZnO NPs was assessed using disk diffusion and DPPH scavenging method, respectively. Molecular docking was further conducted to support our experiments. In addition, the photocatalytic activity of biosynthesized ZnO NPs was tested using methylene blue (MB) dye.
Results: X-ray diffraction (XRD) results indicate that NPs possess a hexagonal wurtzite crystal structure. The crystallite size of the NPs was 30.12 nm. Field emission scanning electron microscopy (FESEM) analysis revealed quasi-spherical and rod-shaped ZnO NPs. Energy Dispersive X-ray (EDX) showed that Zn and O were 86.59% and 13.41% of the total weight, respectively. Optical analysis revealed that the absorption edge was at 373 nm and the band gap was 3.09 eV for ZnO NPs. Moreover, the maximum zone of inhibition was measured at 16.17 ± 0.72 mm, 10.5 ± 0.28 mm, 16.17 ± 0.44 mm, and 12.17 ± 0.44 mm against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Shigella flexneri, respectively. Compared with BHT, ZnO NPs showed promising antioxidant performance with an IC50 value of 149.01 μg/mL. The photocatalytic efficiency of the ZnO NPs was 6.8%, 8.42%, and 10% after 30, 60, and 90 minutes, respectively. Hesperidin, naringin, rutin, and tangeritin, the principal constituents of C. reticulata peel, also showed higher and promising binding affinities against the receptors, with remarkable results compared to the standard in molecular docking analysis. The ADMET analysis also demonstrated that ZnO NPs exhibited low probabilities of hepatotoxicity (3%), nephrotoxicity (20%), and respiratory toxicity (20%), with moderate neurotoxicity (52%).
Conclusion: In summary, this study revealed morpho-structural features of green synthesized ZnO NPs and their photodegradation efficiency and bioactivity.

Keywords: Citrus reticulata, ZnO, nanoparticle, FESEM, XRD, antioxidant, antimicrobial, photocatalytic, molecular docking