Bioscience Evidence 2024, Vol.14, No.3, 98-109 http://bioscipublisher.com/index.php/be 100 accuracy, making it suitable for pharmacokinetic studies (Jeong et al., 2020). Additionally, the biosynthesis of iridoid glycosides in R. glutinosa involves several key genes, such as DXS, DXR, and GPPS, which are upregulated under specific conditions, enhancing the accumulation of these compounds (Dong et al., 2022) (Figure 1). New iridoid glycosides, such as rehmaglutosides L-O, have also been identified, further expanding the understanding of this class of compounds (Liu et al., 2023). Figure 1 Co-occurrence on iridoid glycoside synthetase genes of R. glutinosa(Adopted from Dong et al., 2022) Image caption: (A): Gene co-occurrence of DXS, DXR, GPPS, G10H, and 10HGO in organism; (B): The co-occurrence of DXS, DXR, GPPS, G10H, and 10HGO in plants; Similarity scale: The color indicates the similarity of gene and its homology in the given STRING. Clade coverage: Two distinc tcolors, respectively, denote the lowest and highest similarity observed within the clade (Adopted from Dong et al., 2022) 3.2.2 Phenethyl alcohol glycosides Phenethyl alcohol glycosides, including verbascoside, are another important group of bioactive compounds in R. glutinosa. These glycosides exhibit significant antimicrobial and cytotoxic activities. For example, verbascoside has been found in high concentrations in shoots cultured under specific light conditions, demonstrating its potential for enhanced production through controlled cultivation (Piątczak et al., 2020). The presence of phenethyl alcohol glycosides contributes to the plant's therapeutic effects, such as anti-inflammatory and antioxidant activities (Zhang et al., 2019). 3.2.3 Polysaccharides Polysaccharides from R. glutinosa have garnered attention for their immunomodulatory properties. Rehmannia glutinosa polysaccharide (RGP) has been shown to activate dendritic cells in the mediastinal lymph node, enhancing immune responses. This activation is characterized by increased expression of co-stimulatory molecules and pro-inflammatory cytokines, indicating the potential of RGP as a mucosal adjuvant (Kwak et al., 2018). Additionally, polysaccharides in R. glutinosa leaves and roots have been quantified, revealing significant concentrations that contribute to the plant's overall bioactivity (Xu et al., 2019). 3.2.4 Other minor constituents In addition to the major bioactive components, R. glutinosa contains various minor constituents that contribute to its medicinal properties. These include new compounds such as rehmannia A and ionone rehmannias B-C, which
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