Structural characteristics of areca nut seed neutral polysaccharide and its impact on gut microbiota from human feces

Areca nut (Areca catechu L.) is considered as the fourth most common psychoactive substance globally. Although areca nut seeds (ACS) are typically discarded as processing waste, some studies indicate that amounts of polysaccharides exist in the seeds. However, research on these polysaccharides remains limited. In this study, polysaccharide (ACSP) from areca catechu seeds was isolated into three fractions, among which neutral fraction had a highest yield up to 31.8%. Subsequently, the structural features of neutral fraction (ACSP-0) were analyzed, along with its impact on short-chain fatty acids and human gut microbiota through in vitro feces fermentation. It was found that the backbone chain of ACSP-0 was composed of →4)α-D-Glcp-(1→, α-D-Glcp-(1→, →3,4)α-D-Glcp-(1→ and →4)β-D-Glcp, and the side chain was consisted of α-D-Glcp-(1 → . In vitro digestion experiments demonstrated that ACSP-0 could pass through the upper digestive system without being broken down. Furthermore, in vitro fecal fermentation of ACSP-0 resulted in an increased concentration of short-chain fatty acids and promoted the growth of beneficial bacteria such as norank_f_norank_o_Clostridium UCG-014, which are known to produce generate antibacterial compounds and mitigate gut barrier damage. Additionally, by reducing the abundance ratio of Firmicutes to Bacteroidota, ACSP-0 may hold potential for obesity management. In conclusion, ACSP-0 shows potential as an innovative ingredient for enhancing gut health in humans. This study suggests a novel utilization strategy for areca nut seeds, which could be beneficial for the areca nut processing industry.