An integrated method for efficient isolation and structural elucidation of two homologous polysaccharides from medicinal loquat leaves

A novel ionic liquid/inorganic salt system, [C 14 mim][PF 6 ]/Na 2 CO 3 , was developed for the simultaneous extraction and purification of polysaccharides from medicinal loquat leaves in a single-step procedure. The system forms a homogeneous phase upon heating in water for the polysaccharide extraction and transitions to a solid–liquid two-phase system upon cooling centrifugation for the polysaccharide separation, enabling polysaccharides to partition into the supernatant while proteins and other impurities gather in the sediment. This innovative approach demonstrated superior deproteinization efficiency, achieving a protein removal rate exceeding 99%, significantly outperforming the traditional Sevag method. Crude polysaccharides were further separated into alkali-extracted and water-soluble fractions, followed by purification using DEAE cellulose and Sephadex G-100 chromatography, yielding two homologous polysaccharides, EJp1-1 and EJp2-1. Based on the complementary information, mainly the NMR data, of these two homologous polysaccharides, a new strategy for rapid structure analysis was established. Both EJp1-1 and EJp2-1 were rhamnogalacturonan-I (RG-I) type pectins. EJp1-1 was primarily composed of the RG-I backbone, while EJp2-1 was dominated by the side chains. The side chains of EJp1-1 and EJp2-1 consisted primarily of α-1,5-linked arabinan and β-1,4-linked galactan, which were alternately attached to the O -4-position of rhamnose residues of the repeat RG unit of the main chain. To sum up, this work integrates the efficient extraction, purification and rapid structure analysis of homologous polysaccharides, potentially promoting the sustainable utilization of plant-derived resources.