Structural and rheological properties of polysaccharide from Sida cordata leaves for bio-functional food applications

This study reports the structural, rheological, and bio-functional properties of Sida polysaccharide (SPS)
extracted from Sida cordata leaves. SPS was obtained via aqueous extraction and identified as a branched
rhamnogalacturonan-I (RG-I) type heteropolysaccharide enriched in rhamnose, galactose, and uronic acids, with
a high soluble dietary fibre content (~60 %). Linkage analysis revealed dominant 4-linked galactose (59.6 mol%)
and 3,4-linked glucuronic acid (23.9 mol%), consistent with a branched RG-I backbone carrying uronic acid-rich
domains. FTIR and NMR confirmed typical polysaccharide functional groups, while HPSEC estimated a molec-
ular weight of ~970 kDa. The mineral composition (notably Ca2+ and Mg2+) and broad particle size distribution
(10–1000 μm) were found to modulate hydration and rheological responses. Functionally, SPS exhibited strong
antioxidant activity, maintained cell viability, and inhibited 3 T3-L1 adipocyte differentiation, effects attributed
to its uronic acid content, galactan branching, and high molecular weight. Rheological studies demonstrated
shear-thinning and pH-responsive weak-gel behaviour, further supported by mineral-mediated cross-linking.
When incorporated into vegetable soup, SPS effectively replaced corn starch, enhancing viscosity, mineral
content, and storage stability without compromising sensory quality. These findings highlight SPS as a struc-
turally unique, multifunctional hydrocolloid with potential applications in bio-functional food formulations.