Abstract
Objective: The iridoid glycosides were extracted and separated from Osmanthus fragrans seeds, and the potential protective effect of Osmanthus fragrans seed extract on concanavalin A-induced immune liver injury in mice was studied. Methods: Osmanthus fragrans seeds were extracted by 95% ethanol reflux. Then, the iridoid glycosides were enriched by extraction refined through petroleum ether (60°C–90°C), ethyl acetate, and water-saturated n-butanol in sequence, so as to purify the n-butanol part (Osmanthus fragrans seed’s n-butanol extraction, OFSN) by macroporous resin. Specnuezhenide and Nuezhenoside G13 were used as the reference substances to determine the concentration of iridoid glycosides by HPLC. On this basis, a mouse immune liver injury model was established by tail intravenous concanavalin A (20 mg/kg); the contents of serum ALT, AST, IFN-γ, and TNF-α and the contents of liver tissue MDA and SOD were determined; the pathological changes of the liver by HE staining were observed; and the expression levels of p38MAPK and p-p38mapk in liver tissue were detected by WB. Results: The linearity, precision, repeatability, recovery, and stability of HPLC all met the requirements by validating with the methodology. The contents of Specnuezhenide and Nuezhenoside G13 in the n-butanol extracts were 39.20% and 39.88%, respectively. Actually, their contents can reach up to 82.56% and 87.9% after being purified by macroporous resin. The results of animal experiments show that OFSN could significantly reduce the liver and spleen index, reduce the ALT and AST contents in plasma and the MDA content in liver tissue, and then increase the SOD content. Besides, OFSN could also reduce the plasma IFN-γ and TNF-α levels. The HE staining result indicates that the pathological changes in the liver tissues of mice treated with OFSN are alleviated to different degrees while the WB result suggests that OFSN could significantly inhibit the expression of p-p38mapk. Conclusion: Osmanthus fragrans seeds are rich in iridoid glycosides, which has a good protective effect on mouse immune liver injury caused by concanavalin A. The mechanism may be related to inhibiting the phosphorylation of p38MAPK, inhibiting the release of inflammatory mediators, improving the antioxidant capacity of liver cells, and weakening the occurrence of lipid peroxidation.
Highlights
Osmanthus fragrans Lour. are evergreen shrubs or small trees of the Oleaceae family, which blossom in the autumn and bear fruit in the spring of the following year
The results showed that the linear relationship of Specnuezhenide was good in the range of 24.72–494.41 μg/ml and Nuezhenoside G13 in the range of 24.50–490.00 μg/ml (Figure 3)
Iridoid glycosides extracted from traditional Chinese medicine such as Paederia scandens (Lour.) Merr. var. tomentosa (Rubiaceae) (Peng et al, 2015), Veronica ciliata Fisch (Hua et al, 2020), gardenia (Chen et al, 2016), and rhubarb (Zhu et al, 2014) showed some protective effects on chemical and alcoholic liver injury
Summary
Osmanthus fragrans Lour. are evergreen shrubs or small trees of the Oleaceae family, which blossom in the autumn and bear fruit in the spring of the following year. Osmanthus fragrans seeds are a traditional Chinese medicine, beneficial to liver, stomach, and other diseases. According to the “Compendium of Materia Medica” and “Jiangsu Materia Medica,” Osmanthus fragrans seeds have liver- and stomach-protective effects (Nanjing Pharmaceutical College, 1965; Li, 2007). Modern research shows that Osmanthus fragrans seeds contain a lot of active chemical components (Wang et al, 2006; Pan et al, 2009; Yin et al, 2013; Liao et al, 2018; Liao et al, 2019), such as iridoid glycosides, salidroside, oleanolic acid, ursolic acid, flavonoids, and volatile oil. There are about 10 kinds of iridoid glycosides that have been isolated from Osmanthus fragrans seeds, including nuezhenoside, specnuezhenide, isonuezhenide, nuezhenoside G13, oleoside, oleoside dimethyl ester, and strychnine glycosides, among which the contents of specnuezhenide, isonuezhenide, and nuezhenoside G13 are higher (Yang et al, 2013)
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