Medicinal Plant Research 2025, Vol.15, No.2, 88-98 http://hortherbpublisher.com/index.php/mpr 92 Nowdays, some new purification methods, such as electrodialysis, have also been gradually explored and applied to the separation of flavonoids in Hangbaiju. This method can achieve selective separation based on the molecular charge under mild conditions, effectively reducing the degradation of compounds. Although its specific application in Hangbaiju is still in the exploratory stage, it has a promising future in improving separation efficiency and selectivity. 4.3 Activity retention during separation and purification During the isolation and purification process, the structural stability of flavonoids is easily affected by factors such as pH, temperature, light, and oxygen. For example, a shift in pH from acidic to alkaline during processing or digestion can alter the composition and stability of flavonoids (Song et al., 2022). Mechanical and thermal stress can also trigger the hydrolysis or degradation of glycosides and aglycones (Gong et al., 2021). Studies have found that, with the increase of steam pressure and processing time, the contents of some phenolic acids (like 3-O and 4-O-caffeoylquinic acids) and flavonoid glycosides (e.g., apigenin, luteolin, baicalein) in Hangbaiju increase. The main phenolic acid components, 5-O-caffeoylquinic acid and 3, 5-DI-O-caffeoylquinic acid, decreased (Figure 2). To maximize the bioactivity of flavonoids, process conditions must be controlled to minimize exposure to heat, oxygen, and light, and rapid and gentle separation methods must be employed. For instance, steam explosion pretreatment, when properly optimized in terms of pressure and time, can not only improve flavonoid extraction efficiency, but also release the active ingredients without destroying or even enhancing their antioxidant activity (Gong et al., 2021; Zhu et al., 2024). Rational selection of purification strategies, and process parameters is key to enhancing the functional value of flavonoids from chrysanthemum. Figure 2 Effect of different steam pressure (a) and duration (b) on total phenols content and total flavonoids content in HBJ under steam explosion pretreatment. Control represented HBJ sample without steam explosion pretreatment. Different letters in the same category indicated significant difference at a significant level of 0.05 (Adopted from Gong et al., 2021) Image caption: The figure shows that the total phenolic content and total flavonoid content of Hangbaiju slightly decreased at the initial stage of treatment but gradually increased with the rise in steam pressure or the extension of treatment duration, reaching relatively high levels under conditions of 2.0 MPa and 180 seconds (Adapted from Gong et al., 2021) 5 Functional Evaluation of Hangbaiju Flavonoids 5.1 In vitro activity studies The antioxidant capacity of Hangbaiju flavonoids, has been widely evaluated by standard in vitro methods such as DPPH, ABTS and FRAP. A comparative study of different varieties of Hangbaiju found that, "Taiju" usually contains a higher level of caffeoylquinic acid, and its antioxidant activity is stronger than that of "Duoju", showing a high correlation between phenolic content and antioxidant effect (Gong et al., 2019). After steam blasting pretreatment of Hangbaiju stems and powder, the contents of total phenols and flavonoids increased, thereby enhancing their in vitro antioxidant capacity (Gong et al., 2021; Song et al., 2022; Zhu et al., 2024). Luteolin,
RkJQdWJsaXNoZXIy MjQ4ODYzNA==