Pectic polysaccharides from Pogostemon heyneanus inhibiting enterovirus 71 infection: Structure and antiviral...

This study aimed to characterize antiviral polysaccharides isolated from the aerial parts of Pogostemon heyneanus (PH) against enterovirus 71 (EV71) and evaluate their antiviral effects in vitro and in vivo. Three major polysaccharides (polydispersity index ≤ 1.29), namely PH50-c2 (21.9 kDa), PH80-b3 (10.6 kDa), and PH80-c3 (27.4 kDa), were isolated from an aqueous PH extract. The major component sugar was 1,4-α-GalAp, with the highest molar content in PH50-c2 (74.8%), followed by PH80-c3 (52.8%) and PH80-b3 (49.7%). The degree of methyl esterification, as determined by FT-IR, and the degree of branching were lowest in PH50-c2 (8.2% and 13.4%, respectively) and similar in PH80-b3 (12.4% and 25.0%, respectively) and PH80-c3 (12.5% and 22.4%, respectively). Linkage analysis and nuclear magnetic resonance spectroscopy confirmed that these polysaccharides are pectins comprising a homogalacturonan backbone and rhamnogalacturonan I side chains. The purified polysaccharides exhibited potent antiviral activities against EV71, but were not or less effective against coxsackievirus, human rhinovirus, and influenza A virus. PH50-c2 exhibited the strongest anti-EV71 activity (IC₅₀ = 0.4 μg/mL), followed by PH80-c3 (0.8 μg/mL) and PH80-b3 (10.1 μg/mL), indicating that charge and molecular size of pectic polysaccharides may act complementarily to enhance antiviral activity. PH50-c2 suppressed viral protein levels in infected cells and inhibited early-stage EV71 infection. In an hSCARB2-transgenic mouse model, PH50-c2 reduced EV71-induced body weight loss, paralytic symptoms, and mortality. These findings suggest that pectic polysaccharides from PH have potential as natural antiviral candidates against EV71 infection.