Bioscience Evidence 2024, Vol.14, No.2, 56-68 http://bioscipublisher.com/index.php/be 61 Figure 2 Effect of 5-azaC on iridoid glycoside accumulation in R. glutinosa(Adopted from Dong et al., 2022) Image caption: (A) and (B) respectively show the content of iridoid glycosides in the roots and leaves of R. glutinosa at different growth stages (E, I, M). The results indicate that 5-azaC treatment significantly increased the content of iridoid glycosides in the roots at all growth stages, with the most pronounced effect observed at the 50 µM treatment. In the leaves, the accumulation of iridoid glycosides also increased, although not as significantly as in the roots. This suggests that 5-azaC plays an important role in regulating the accumulation of secondary metabolites inR. glutinosa(Adapted from Dong et al., 2022) 6.2 Anti-inflammatory effects Rehmannia glutinosa also possesses significant anti-inflammatory properties. The oligosaccharides (RGO) isolated from Rehmannia glutinosa have been shown to combat lipopolysaccharide (LPS)-induced intestinal inflammation by reducing the levels of inflammatory cytokines. The study by Li et al. (2023) indicates that the oligosaccharides extracted fromRehmannia glutinosa (RGO) provide significant protection against LPS-induced intestinal inflammation and barrier damage in a mouse model. RGO decreased the levels of inflammatory cytokines (e.g., IL-6, IL-17, IL-1β, and TNF-α) in intestinal tissues, increased the activities of antioxidant enzymes (SOD, GSH-Px, and CAT), and reduced the content of MDA (Figure 3). Furthermore, the polysaccharides from R. glutinosa attenuate colitis by inhibiting the NF-κB pathway, thereby reducing the expression of inflammatory factors and improving intestinal health (Lv et al., 2022). The anti-inflammatory activity is also evident in the suppression of nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in various models (Rahmat et al., 2022). 6.3 Neuroprotective actions The neuroprotective effects of Rehmannia glutinosa are largely attributed to catalpol, an iridoid glycoside found in the plant. Catalpol has been shown to protect against spinal cord injury by inhibiting endoplasmic reticulum (ER) stress-mediated neuronal apoptosis, thereby preserving motor function and reducing neuronal death (Huang et al., 2022). Additionally, catalpol's neuroprotective mechanisms include the elevation of serotonin and brain-derived neurotrophic factor (BDNF) levels, which protect against depression and neurodegeneration (Bhattamisra et al., 2019).
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