Effects of Different Extraction Methods on Physicochemical Properties and Antioxidant Activity of Apocynum venetum Polysaccharides

In this paper, the effects of hot water extraction (HWE), ultrasonic-assisted extraction (UE), cellulase assisted extraction (CE), pectinase assisted extraction (PE), and ultrasonic microwave assisted extraction (UME) on the physicochemical properties and activities of polysaccharide from Apocinae venetiana (AVP) were studied. The results showed that the extraction rate in the order of AVP-PE (13.6%)>AVP-CE (13.4%)>AVP-UME (12.4%)>AVP-UE (12.1%)>AVP-HWE (9.2%). The polysaccharides obtained by different extraction methods were mainly composed of arabinose, glucose and galactose in a different molar ratio, however, the proportion of each monosaccharide was different. The arabinose was the predominant monosaccharide for AVP-HWE and AVP-CE, and glucose for the others. Different polysaccharides exhibited typical infrared absorption peaks of polysaccharide compounds without a triple helix structure, and showed different surface structures. The polysaccharides demonstrated strong antioxidant activity, among which AVP-HWE had the strongest DPPH and ABTS+ free radicals scavenging ability, with half inhibition concentrations (IC50) of 0.219 and 0.072 mg/mL, respectively. AVP-UE had the strongest hydroxyl radical scavenging ability, with IC50 of 0.298 mg/mL. AVP-CE had the strongest ferrous ion chelating ability, with IC50 of 0.107 mg/mL, and there were few differences for the total reducing power between different polysaccharides. In summary, different extraction methods have a significant impact on the structure and activity of AVP, and UE and CE are more suitable for the extraction of AVP. This paper may be providing reference for the development and utilization of polysaccharides resources from Apocynum venetum leaves.