Polysaccharides from Oplopanax elatus adventitious root residues: Purification, antioxidant properties, and probiotic growth promotion

The large-scale in vitro culture of Oplopanax elatus Nakai adventitious roots (ARs) has opened new possibilities for utilization of this endangered medicinal plant. However, a significant amount of AR biomass remains unused after the initial ethanol extraction process. In this study, crude polysaccharides (ARCP) were recovered from AR residues and purified using macroporous resin adsorption to obtain purified polysaccharides (ARPP). Response surface methodology (RSM) was employed to optimize the purification process. Under the optimal conditions of 0.81 mg/mL sample concentration, 1.93 bed volumes (BV) sample volume, 19.44 % eluent concentration, and 1.94 BV eluent volume, the average polysaccharide content was 357.99 mg/g. Structural characterization using scanning electron microscopy, fourier-transform infrared spectroscopy, and monosaccharide composition analysis revealed that ARPP had a more compact morphology and a more distinct sugar profile than ARCP. The dominant monosaccharides were L-arabinose, D-glucose, and D-galactose. Bioactivity assays demonstrated that ARPP possessed significantly higher antioxidant activity, as evidenced by lower EC₅₀ values in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺), superoxide anion (O 2 ·- ) radical scavenging, and ferrous ion (Fe²⁺) chelation assays. Additionally, ARPP exhibited superior growth-promoting effects on Lactobacillus strains, particularly L. plantarum and L. reuteri . The results of this study suggest that ARPP is a promising multifunctional ingredient with antioxidant and prebiotic potential. It provides an efficient strategy for utilizing O. elatus AR residues. • Residues from ethanolic extraction of Oplopanax elatus adventitious roots (AR) were recycled. • AR residues yielded high-purity polysaccharides via macroporous resin purification. • Purified polysaccharides (ARPP) showed significantly enhanced antioxidant activities. • ARPP promoted the growth of Lactobacillus , especially L. plantarum and L. reuteri . • This study provides a green strategy for utilizing plant cell culture extraction residues.