Citrus peel essential oil (CPEO) is favored by people for its aromatic scent, while also possessing numerous bioactive compounds that are advantageous to human health. This study evaluated the antioxidant, anti-inflammatory, and anticancer activities of CPEOs through cell experiments. The results showed that CPEOs could increase the activity of the antioxidant enzyme system and nonenzymatic defence system in H₂O₂-treated RAW 264.7 cells by reducing cellular lipid peroxidation. CPEOs also reduced the nitric oxide production induced by lipopolysaccharide treatment in RAW 264.7 cells while decreasing proinflammatory cytokines expression and increasing anti-inflammatory cytokine expression. Wound healing assays, flow cytometry, and quantitative real-time fluorescent quantitative PCR (qRT-PCR) revealed that CPEOs could induce apoptosis in U87 cells through the mitochondrial apoptotic pathway. These findings indicate that CPEOs possess excellent antioxidant, anti-inflammatory, and anticancer activity potential, making them suitable for use in functional antioxidant and anti-inflammatory foods and nutritional health products.

Introduction: Currently, the large-scale consumption of fresh citrus fruits in the form of juices, jams, and purees results in significant quantities of waste consisting of citrus peels, pulp, and seeds.Methods: To improve the utilization rate of whole citrus fruits and reduce the generation of processing waste, the best pre-optimized enzymatic fermentation conditions were used to treat whole citrus fruits and to analyse the changes in nutritional and active components (Enzymatic: pectinase, cellulase, hemicellulase added at a ratio of 1:1:1 for 63.326 min at a temperature of 60°C, with 0.506% of each enzyme added; Fermentation: Lacticaseibacillus rhamnosus TR08, Lactiplantibacillus plantarum subsp. Plantarum CICC 6257, and Limosilactobacillus fermentum CCFM1139 were added at a ratio of 1:1:1 for 30 h, with the concentration was 10⁸ CFU/mL, and the total amount added was 6%).Results: Results showed that after enzymatic hydrolysis, the mineral elements (Nitrogen, phosphorus), total amino acid, vitamin C, and organic acid content increased. For soluble sugars, the contents of fructose and glucose increased, whereas the sucrose content decreased. Fermentation had a minimal effect on the mineral content; however, the total amino acid, vitamin C, and soluble sugar contents decreased. Additionally, when comparing the samples after enzymatic fermentation to those after enzymatic hydrolysis alone, the total phenols, total flavonoids, carotenoids and antioxidant activities were significantly increased by 1.39, 1.49, 1.21 and 3.79 folds, respectively.Discussion: This study addresses the challenges of utilizing fruit residue in the current market, including high treatment costs and environmental pollution, by providing a novel perspective on the enzymatic hydrolysis and fermentation of whole red oranges. Furthermore, it aims to improve the nutritional, functional, and health benefits of citrus fruit products.

Citrus peel essential oils (CPEOs) have demonstrated substantial medicinal potential for glioblastoma treatment because of their extensive antitumor effects, low potential for drug resistance, and ability to cross the human blood–brain barrier. In this study, the chemical compositions of five CPEOs were analyzed via gas chromatography–mass spectrometry (GC-MS). CCK8 assays were used to evaluate the ability of five CPEOs to inhibit U251 human glioblastoma cells, and XLB and RA were selected for further investigation. Through wound healing assays and cell cycle and apoptosis analyses via flow cytometry, it was revealed that these CPEOs inhibited cell migration, arrested the cell cycle at G1/G0, and induced apoptosis with similar levels of inhibition. After CPEOs treatment, the intracellular Ca²⁺ content and reactive oxygen species levels in U251 cells increased significantly, whereas the mitochondrial membrane potential decreased. Additionally, the antioxidant enzyme system (SOD, POD, CAT, and GR) and the nonenzymatic defense system (GSH) were inhibited, leading to an increase in lipid peroxidation. qRT–PCR indicated the significant upregulation of intracellular calcium ion signaling pathways and the upregulation of mitochondrial apoptosis-related genes. Additionally, the activation of calcicoptosis-related indicators induced by the CPEOs could be reversed by inhibitor treatment, confirming that both of the selected CPEOs inhibit tumors by activating calcicoptosis-related pathways. These findings highlight the immense potential of CPEOs in healthcare and pharmaceutical applications by not only providing a scientific basis for the potential application of CPEOs in the treatment of glioblastoma but also offering new insights for the development of novel antitumor drugs.