Comprehensive Physicochemical Characterization and Bioactive Profiling of Citrus sinensis Peel Essential Oil

Introduction: The growing demand for sustainable and environmentally benign bioresources has intensified research into the valorization of agro-industrial wastes, particularly Citrus peels, which are rich in essential oils with diverse functional and biological properties. Understanding the physicochemical characteristics and bioactive composition of Citrus sinensis peel essential oil (CSPEO) is critical for establishing its structure-function relationships and potential applications. Aim: This study aimed to comprehensively characterize the physicochemical properties and bioactive constituents of Citrus sinensis peel essential oil in order to evaluate its functional attributes and suitability as a value-added, sustainable bioresource. Materials and Methods: Essential oil was extracted from freshly chopped Citrus sinensis peels using hydrodistillation with a Clevenger-type apparatus. The oil was characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and gas chromatography-mass spectrometry (GC-MS) to assess its optical behavior, functional groups, morphology, structural organization, and chemical composition. Results: UV-Vis analysis revealed a strong absorption maximum in the ultraviolet region around 300-320 nm with an absorbance of approximately 0.81, indicating the presence of UV-active phytochemicals. FTIR spectra showed characteristic bands corresponding to O-H stretching (3200-3600 cm⁻¹), aliphatic C-H stretching (2850-2950 cm⁻¹), and C=O stretching near 1700-1740 cm⁻¹, confirming a chemically diverse terpene-rich matrix. SEM micrographs at 9000× and 10,000× magnifications revealed a heterogeneous, porous, and irregular surface morphology. XRD patterns displayed a broad diffuse halo between 15° and 25° (2θ), confirming the predominantly amorphous nature of CSPEO. GC-MS profiling identified monoterpene hydrocarbons as the dominant constituents, with limonene-related bicyclic monoterpenes accounting for over 90% of the total composition, while minor oxygenated terpenes were present in trace amounts. Conclusion: The integrated physicochemical and chemical analyses demonstrate that Citrus sinensis peel essential oil possesses UV-active behavior, diverse functional groups, favorable amorphous structure, and a terpene-dominated bioactive profile. These attributes collectively highlight CSPEO as a promising value-added product derived from citrus peel waste, with potential applications in eco-friendly biological control, natural product formulations, and sustainable green technologies.