Comparison in bioactivity and characteristics of Ginkgo biloba seed polysaccharides from four extract pathways

The effects of hot-water extraction (HWE), ultrasound-treated extraction (UTE), enzyme-treated extraction (ETE) and ultrasound-enzyme treated extraction (UETE) on the α-glucosidase inhibitory activity, antioxidant activities and characteristics of Ginkgo biloba seed polysaccharides were investigated and compared in this study. Among the four extracted polysaccharides, the UETE-polysaccharide initially exhibited the highest α-glucosidase inhibitory activity and antioxidant activities. The HWE-polysaccharide showed a large number of small compact spherical structures, and the UTE-polysaccharide exhibited an irregular pleated porous shape; meanwhile, the ETE-polysaccharide and UETE-polysaccharide were spongy with smooth surface topography, as observed by scanning electron microscopy (SEM). The four polysaccharides varied in monosaccharide composition. The HWE-polysaccharide mainly consisted of homogeneous mannose; the UETE-polysaccharide was primarily composed of mannose, rhamnose, and glucose in a molar ratio of 8.25:1.00:1.53. The HWE-polysaccharide had the largest molecular weight (4.2 × 105 Da), reduced by the order of the UETE-polysaccharide (2.02 × 104 Da), ETE-polysaccharide (1.72 × 104 Da), and UTE-polysaccharide (1.34 × 104 Da). Thus, the four extract methods exerted significant effects on the bioactivity and characteristics of the polysaccharides. The UETE-polysaccharide from G. biloba seeds showed the highest bioactive activities and distinctive structural characteristics.