Characterization, and Anti-microbial Properties of Zinc Oxide Nanoparticles Synthesized Using Citrus sinensis (L.) Osbeck Peel Extract
Authors: Khanal Dharma Prasad , Aryal Sadikshya , Aryal Samyam 
Published: October 2020

ABSTRACTBackgroundCitrus sinensis (L.) Osbeck peels are usually discarded as wastes; however, they are rich sources of Vitamin C, fibre, and many nutrients including phenolics and flavonoids which are also good antioxidant agents. This study aimed to examine phytochemical composition, antioxidant capabilities, cytotoxicity of C. sinensis (L.) Osbeck peel extract and and to compare the antibacterial activity with zinc nanoparticles of Citrus sinensis (L.) Osbeck peels with its extract. GC-MS analysis of the compounds present in the peels extract of Citrus sinensis (L.) Osbeck was also done.MethodsC. sinensis (L.) Osbeck fruits were collected from Sindhuli district and were taken to National Herbarium and Plant Laboratory, Godawari, Lalitpur for its identification. Extraction was done by maceration in aqueous solvent. Extract was subjected to Phytochemical screening done by color reactions with different reagents, Antioxidant activities of the peel extracts were examined via the 2,2-diphenylpicrylhydrazyl (DPPH) free radical scavenging activity. Total phenolic content and total flavonoid content of the extracts were measured via the Folin-Ciocalteau method and the aluminium chloride colorimetric method, respectively. Cytotoxic activities of the peel extracts were determined by Brine Shrimp Lethality Bioassay. Comparison of antibacterial activity of extract and zinc oxide nanoparticles prepared via green synthesis using C. sinensis (L.) Osbeck peel extracts as reducing agents. Antibacterial activity was tested by Bore well diffusion method.ResultThe extractive value of C. sinensis (L.) Osbeck was found to be 8.64% in aqueous solvent. GC-MS analysis of peel extract of C. sinensis (L.) Osbeck showed the presence of 2-Methoxy-4-vinylphenol, 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl, Benzoic acid, 3-Deoxy-d-mannoic lactone and 5-Hydroxymethyl-furfuralas major compounds. The qualitative phytochemical test showed the presence of tannin, alkaloid, carbohydrate, flavonoid, cardiac glycoside, terpinoid.The DPPH radical scavenging activity of C. sinensis (L.) Osbeck peel extract was 35.56 μg/ml. TPC of C. sinensis (L.) Osbeck peel extracts was 46.07 mg GAE/g. TFC was 1.29 mg QE/g. The LD50 value of Brine Shrimp Lethality assay of the extract showed 312.5μg/ml which is indicative. The antibacterial activity of zinc oxide nanoparticles was found to be greater than that of the extract, but the antibacterial activity of Zn-NPs was less than that of the standard.ConclusionHence, the GC-MS analysis of aqueous extracts of leaves of C. sinensis (L.) Osbeck showed the presence of 20 different compounds. Phytochemicals including phenolics and flavonoids in C. sinensis (L.) Osbeck peel extracts exhibited good antioxidant properties. The extract also exhibited antibacterial activity which was 4 times less than that of the standard. The antibacterial activity of standard was 2 times greater than that of Zn-NPs. The extract also exhibited cytotoxic activity. This study indicated that C. sinensis (L.) Osbeck peels contained potential antioxidant, cytotoxic and antibacterial compounds which could be exploited as value added products.