Structural characterization, antioxidant activity, and the effects of Codonopsis pilosula polysaccharides on the solubility and stability of flavonoids

Codonopsis pilosula (CP) possesses properties related to nourishing the spleen and stomach, and tonifying Qi of the stomach and mind in traditional Chinese medicine (TCM). Codonopsis pilosula polysaccharides (CPPS), which are the primary active components of CP, are thought to be in charge of their extensive use. Rutin, quercetin, luteoloside, and luteolin, are common and pharmacologically significant flavonoids with many pharmacological activities, but their oral bioavailability is limited by poor solubility and stability. In this study, high-performance gel permeation chromatography (HPGPC) estimated the molecular weight of CPPS to be 9.7 × 10⁵ Da. Sugar analysis revealed that CPPS is composed of D-mannose, D-glucose, and D-xylose with a molar ratio of 5.8:1.9:1.0. Moreover, the antioxidant test showed that CPPS had good antioxidant activity. It is worth noting that CPPS integrated the four flavonoids to form a spongy compound that significantly increased the solubilities and stabilities of flavonoids. The bonding constants of the CPPS and flavonoid-derived inclusion complexes ranged from 60 L mol^-1 to 2,030,816 L mol^-1, which demonstrated the capacity of CPPS to interact with flavonoids intermolecularly to form a drug complex system, resulting in potentially enhanced biopharmaceutical properties of flavonoids. This finding could provide a reference point for further applications of polysaccharides from herbal medicines.