Naringin, also known as heteroside, citrus glycoside, and neohesperidin, has the chemical name of 4,5,7-trihydroxyflavanone-7-rhamnoside. It is a colorless needle-like crystalline powder, difficult to dissolve in cold water, and has an extremely bitter taste. Its chemical structure is shown in the figure below. As a natural flavonoid compound, naringin is the main medicinal component of traditional Chinese medicines such as Drynaria fortunei, Fructus aurantii immaturus, Fructus aurantii, and Exocarpium Citri Grandis. Modern pharmacological research has found that naringin has effects on anti-osteoporosis, antioxidation, anti-inflammation, antibacterial, anti-tumor, improvement of myocardial and liver damage, prevention and treatment of diabetes and its complications.

1、Prevention and treatment of osteoporosis

Bone tissue in the human body maintains a dynamic balance between formation and resorption. On one hand, osteoblasts form new bone; on the other hand, osteoclasts break down old bone. When this dynamic balance is disrupted, bone loss can lead to osteoporosis. Studies have shown that naringin has significant advantages in the treatment of osteoporotic bone damage, with effects on preventing and treating osteoporosis, promoting fracture healing, and repairing cartilage damage. Research indicates that naringin can inhibit the differentiation, proliferation, and bone resorption function of osteoclasts, and its mechanism is achieved by inhibiting the expression of specific genes during osteoclast differentiation.

Naringin can increase the expression of osteoblast marker proteins such as osteocalcin, osteopontin, osteoprotegerin, and bone morphogenetic protein-2 (BMP-2). At the same time, it can inhibit RANKL (The receptor activator of nuclear factor-kappa B (NF-κB) ligand) induced NF-κB and ERK signaling activities and osteoclast gene protein expression, thus preventing osteoclasts from forming normally. Therefore, it plays a role in delaying osteoporosis and promoting the proliferation and differentiation of osteoblasts. Studies have shown that bone loss induced by nerve resection is associated with the inactivation of Wnt/β-catenin and the upregulation of periostin and its downstream sclerostin. Naringin can upregulate the expression of periostin and prevent nerve resection-induced bone mineral density (BMD) reduction, ultimately preventing the deterioration of bone microstructure and mechanical properties. In addition, studies have also confirmed that naringin can inhibit osteoclast differentiation and bone resorption function; inhibit osteoclast proliferation activity, significantly downregulate the expression of RANK, TRAP, MMP-9, NFATc1 mRNA, and upregulate the expression of C-fos mRNA during osteoclast differentiation.

Research has shown that naringin promotes fracture healing and improves osteoporotic fractures in rats, which is associated with its upregulation of bone morphogenetic protein-7 (BMP-7) and basic fibroblast growth factor (bFGF) proteins, as well as an increase in femoral bone mineral density (BMD). Simultaneously, it has been found that naringin can reduce bone mass coefficient, bone length, bone ash content, calcium, and phosphorus content in model rats, significantly improving symptoms of osteoporosis in rats. Furthermore, studies have revealed that naringin not only enhances rat BMD, trabecular thickness, bone mineralization, and mechanical strength in a dose-dependent manner but also significantly reduces bone resorption in vitro. Through observing the interaction between naringin and experimental rabbit knee joint cartilage injury models, it was discovered that naringin can promote the reduction of cartilage injury area and the growth of granulation tissue in the model group. Experiments using the mouse monocyte RAW264.7 cell line have shown that naringin can inhibit the number and activity of mouse osteoclasts by downregulating the expression of B-cell lymphoma-2 (Bcl-2) and matrix metalloproteinases-9 (MMP-9), while promoting the expression of B cell lymphoma-2 associated X protein (Bax) and cystein-asparate protease-3 (Caspase-3), further promoting their apoptosis. Additionally, it can also promote osteoblast activity through synergistic expression with BMP-2.

2、Antitumor Effects

Naringin exhibits certain effects in fighting against tumor cells such as osteosarcoma, glioma, cervical cancer, colon cancer, lung cancer, and thyroid cancer. Its mechanism may be related to directly damaging the growth, proliferation, and migration of tumor cells. At the same time, its ability to induce and enhance the antitumor immune response of macrophages, synergize and enhance the activity of antitumor drugs, and reduce the drug resistance of tumor cells, may also be effective ways to inhibit tumor cells.

Researches have shown that naringin has certain advantages in anti-tumor aspects, and it has a significant inhibitory effect on various tumor cells, including osteosarcoma MG63 cells and glioma U87 cells. Naringin can enhance the expression of IL-1β, IL-12, and CD169 in local lymph nodes of mice, and it can strengthen the anti-tumor immune response of the body by inducing CD169-positive macrophages in lymph nodes. In addition, numerous studies have indicated that naringin can not only promote the apoptosis of cervical cancer HeLa cells, inhibit the proliferation and migration of HeLa cells, but also enhance the inhibition rate and apoptosis rate of colon cancer SW620 cells. Furthermore, some scholars have found that naringin can also enhance the efficacy of cisplatin, reduce the drug resistance of human lung cancer A549 cells, cooperate with cisplatin to inhibit A549 cells, and effectively prolong the survival period of lung cancer patients. Naringin can not only inhibit the growth of human lung cancer H69AR cells, but also promote their apoptosis. The study on the effect of naringin on thyroid cancer SW1736 cells found that it can also inhibit the proliferation of SW1736 cells, induce their apoptosis, and has a certain anti-thyroid cancer effect.

3、Antioxidant Effect

Naringin possesses significant antioxidant properties and is capable of improving oxidative damage, demonstrating potential pharmacological value for development as a natural antioxidant. Its main antioxidant mechanism involves scavenging free radicals such as DPPH, AAPH, and ABTS, counteracting their attacks on cells, inhibiting the production of ROS, blocking oxidative reactions in the body, and restoring oxidative stress damage in the body by regulating the levels of various oxidases such as SOD, GSH, GST, MDA, and MPO.

The molecular structure of naringin contains hydroxyl groups, which can react with harmful free radicals to become more stable semiquinone radicals, thus exerting an antioxidant effect. By comparing the scavenging ability of naringin and ascorbic acid on 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, it was found that naringin has a better ability to scavenge DPPH free radicals. Other studies have also found that naringin can not only scavenge superoxide free radicals and DPPH free radicals in liver cells of model rats, but also antagonize the attack of 2,2′-azobis-2-methyl-propanimidamide (AAPH) free radicals on red blood cells, protecting red blood cells and significantly reducing the hemolysis rate of red blood cells under oxidative stress conditions. It is also pointed out that when the mass concentration of naringin is 8 μg/mL, it has the strongest scavenging effect on 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals. Studies have shown that the behavior, oxidative stress, and mitochondrial enzyme complex function of Huntington's disease induced by 3-nitropropionic acid are improved after the action of naringin. Naringin can protect DNA oxidative damage induced by peroxynitrite and inhibit the expression of nitric oxide synthase and cyclooxygenase, which is mainly manifested by scavenging reactive oxygen species (ROS) and reactive nitrogen species (RNS). Naringin can also reduce oxidative damage and RIN-5F cell apoptosis associated with HIV-1 protease inhibitors in pancreatic β-cells. In cells treated with HIV-1 protease inhibitors and then treated with naringin, it can significantly reduce lipid peroxidation, increase superoxide dismutase activity, glutathione (GSH) and ATP levels, and also reduce the activity of caspase-3 and caspase-9. Naringin has a bidirectional effect of increasing SOD and catalase (CAT) activity in mouse skin damage tissue caused by ultraviolet radiation, and reducing MDA and ROS content.

4、Antibacterial and Anti-inflammatory Effects

Research has shown that naringin possesses good anti-inflammatory properties. It can improve inflammatory damage induced by lipopolysaccharide (LPS) and inhibit the protein and gene expression levels of interleukin-6 (IL-6), IL-8, and IL-1β in inflammatory models, as well as reduce the concentrations of leukotriene B4 (LTB4) and tumor necrosis factor-α (TNF-α). At the same time, it was found that the combined application of naringin and sericin exhibited significantly stronger inhibitory effects on relevant inflammatory factors compared to the use of naringin or sericin alone, indicating that the combined use of naringin has important significance in improving clinical efficacy, enhancing the tolerance of the body to drugs, and achieving optimal anti-inflammatory effects. Furthermore, other studies have shown that naringin can inhibit rheumatoid arthritis (RA) in rats by suppressing inflammatory factors such as IL-17 and IL-10, and the inhibitory effect is dose-dependent. When the dose of naringin is 200 mg/kg, it has significant inhibitory effects on osteoarthritis both in vivo and in vitro. The mechanism is related to the antagonism of IL-1β and the inhibition of inflammatory signaling pathways such as nuclear factor-κB (NF-κB) and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3).

Naringin plays a significant role in the prevention and treatment of relevant pathogenic bacteria. Studies have found that the minimum inhibitory concentration (MIC) of naringin against Streptococcus mutans, S. sanguis, S. sobrinus, Actinomyces viscosus, A. naeslundii, and Lactobacillus acidophilus is 1, 0.5, 0.5, 0.5, 1, and 1 g/L, respectively. The minimum bactericidal concentration (MBC) is 2, 1, 1, 1, 2, and 2 g/L, respectively. It has also been found that naringin can disrupt the normal growth, acid production, sugar production, and adhesion functions of the above pathogenic bacteria. At the same time, other studies have shown that the inhibitory effect of naringin on Actinomyces viscosus and Porphyromonas gingivalis is time- and concentration-dependent. Furthermore, by comparing the combined therapeutic effects of naringin, antibiotics (ciprofloxacin and tetracycline) on Pseudomonas aeruginosa biofilms, it was found that compared to monotherapy, naringin can enhance the efficacy of ciprofloxacin and tetracycline on Pseudomonas aeruginosa biofilms.

5、Relief Effects on Diabetes

Naringin possesses significant value in the treatment of diabetes and its complications. Its mechanisms include: ① inhibiting ketoacidosis and lipid peroxidation in the body; ② regulating the protein expression of TC, TG, and LDL-C; ③ activating the AMPK-GLUT4 protein expression pathway, promoting glucose metabolism, and reducing insulin resistance; ④ reducing ECM accumulation and increasing MMP-2 expression; ⑤ reducing the accumulation of free radicals, SOD, ROS, and CAT, and inhibiting oxidative stress damage. Studies have shown that naringin can control renal dysfunction and the degree of injury by alleviating oxidative stress induced by streptozotocin, inhibiting apoptosis induced by high glucose, and reducing reactive oxygen species levels. It can significantly inhibit the expression of oxidase NOX4 mRNA and its protein levels. Research on the pharmacological effects of naringin on experimental type 2 diabetes mellitus (T2DM) rats also indicates that it can improve the disrupted glucose and lipid metabolism, alleviate insulin resistance, enhance the body's antioxidant capacity, and protect the liver in T2DM rats.

6、Improvement of Myocardial and Liver Damage

Naringin has a certain improvement effect on experimental myocardial damage caused by common factors both in vivo and in vitro. Its mechanism is related to naringin's regulation of intracellular apoptosis-related factor protein expression, inhibition of myocardial tissue protein phosphorylation, and blockage of the activation of the NF-κB inflammatory pathway after myocardial ischemia-reperfusion injury (MI/RI) and hypoxia-reoxygenation injury (H/R). Numerous studies have shown that naringin can improve MI/RI caused by various reasons. It not only inhibits the phosphorylation of the inhibitor of NF-κBα (IκBα) protein in myocardial tissue, blocks the activation of the NF-κB pathway after MI/RI, but also improves the damage to H9c2 cells, a H/R-type myocardial cell line, and reduces the apoptosis rate. In addition, other studies have found that naringin can also improve H9c2 cell damage induced by H2O2 (oxidative stress type) and high glucose (high glucose toxicity type) by downregulating the expression levels of IL-6 and NF-κB proteins.

Naringin has significant pharmacological effects in the prevention and treatment of experimental liver damage. Its mechanism is related to naringin's ability to significantly reduce CYP450 activity, inhibit phase I enzyme metabolism, promote phase II enzyme metabolism, and eliminate the damage caused by exogenous substances to liver cells. It is also related to the regulation of various intracellular oxidase levels, inhibition of liver cell oxidative damage and apoptosis, and further repair of damaged liver cells.

References

[1] Yang Xinrong, Dou Xia, Li Guofeng, et al. Research progress on the pharmacological effects and mechanisms of naringin [J]. Chinese Traditional and Herbal Drugs, 2022, 53(10): 3226-3240.

[2] Jin Yuanbao, Liu Ping, Liu Xiaogen, et al. Research progress on the biological activities of naringin [J]. Chinese Journal of Modern Medicine, 2018, 20(03): 92-97.

About the Author

Xiaomichong, a pharmaceutical quality researcher, has been committed to pharmaceutical quality research and drug analysis method validation for a long time. Currently employed by a large domestic pharmaceutical research and development company, she is engaged in drug inspection and analysis as well as method validation.