Natural polysaccharides extracted from herbal medicines: Focusing on the chemical modification of polysaccharides and their prospects in medical applications

Humans have been using herbal medicines to treat diseases for thousands of years, and. numerous studies have shown that polysaccharides extracted from various herbal medicines play an important role in disease treatment. These herbal medicine polysaccharides possess several unique biological activities, such as immunomodulation, antimicrobial, antitumor, anti-inflammatory, and antioxidant effects. Additionally, they are widely available and exhibit good biocompatibility and biodegradability, which has attracted more researchers to study herbal medicine polysaccharides extensively. During these studies, many researchers have found that chemically modifying the molecular structure and conformation of herbal medicine polysaccharides can enhance certain biological activities or even introduce new ones. In this paper, we review some representative herbal medicine polysaccharides, discussing different chemical modification methods, comparisons of biological activities before and after modification, and their potential applications in the future, aiming to provide a reference for further research on the chemical modification of herbal medicine polysaccharides. Compared with previous reviews that mainly enumerate modification methods, this review emphasizes the novelty of linking modification chemistry with structure-activity rules (degree and site of substitution, molecular-weight distribution, and higher-order conformation), de novo activities generated by modification, nanocomplex delivery behavior, safety evaluation, and industrial translation bottlenecks.