Study On Modification Of The Lucuma Nervosa Flesh Polysaccharide And Its Biological Activity

Lucuma nervosa A.DC is a plant of the sapotaceae and peach olive families,nati ve to tropical regions such as Cuba and North America,and only rarely cultivated in China’s Hainan and Yunnan provinces.Fruit flesh is high in dietary fiber,sugars,mine rals,vitamins,fats,proteins,and other nutrients,making it an excellent food resource with a wide and potential market.Flesh has a variety of biological functions,includin g antioxidant,immune,anticancer,and weight loss.As we know,polysaccharide struct ural modification can aid in improving biological activity and identifying derivative str uctures of Lucuma nervosa flesh polysaccharides with high biological activity.It has si gnificant research value for exploring the true potential of modified polysaccharides fr om Lucuma nervosa as a source of new plant drugs,as well as further improving the comprehensive and product utilization of Lucuma nervosa.Using Lucuma nervosa fle sh as a raw material,we optimized the process of modified flesh polysaccharide and i nvestigated the in vitro antioxidant and hypoglycemic activities.The following conclusi ons have been reached:（1）Response surface methodology was used to optimize the preparation process of acetylated Lucuma nervosa flesh polysaccharide（Ac-PCPP-11）and sulfated Lucuma nervosa flesh polysaccharide（S-PCPP-11）.The results indicate that the influence factors on the degree of substitution in the preparation process of Ac-PCPP-11 according to reaction time>reaction temperature>liquid to material ratio.Under the best condition with a reaction temperature of45°C,a reaction time of 3 h and a liquid/material ratio of 28:1 m L/g,Ac-PCPP-11 with 0.587of degree of substitution were produced.The influence factors on the degree of substitution in the preparation process of S-PCPP-11 was reaction temperature,followed by pyridine-chlorosulfonic acid molar ratio and reaction time.The best degree of substitution for S-PCPP-11 was 0.468,obtained from the conditions of a pyridine-chlorosulfonic acid molar ratio of 2:1,a reaction temperature of 65°C and a reaction time of 3 h.（2）The structures of Lucuma nervosa flesh polysaccharide（PCPP-11）,AC-PCPP-11,and S-PCPP-11 were characterized and resolved by HPLC,HPGPC,FT-IR,NMR,SEM and UV.The findings indicate that Ac-PCPP-11 and S-PCPP-11 without protein and nucleic acid;Ac-PCPP-11 and S-PCPP-11 had retention times of 7.5 minutes and Mw of 88.85 k Da and82.868 k Da,respectively;Ac-PCPP-11 and S-PCPP-11 with molar ratios of Glc、Gal and Ara were 88.2:6.78:5.02 and 45.9:27.7:26.4 respectively;all of PCPP-11,Ac-PCPP-11,and S-PCPP-11 have absorption peaks of polysaccharide and D-glucopyranoside bond.Ac-PCPP-11 was the characteristic absorption peak of acetylation at 1740 cm^-1.S-PCPP-11has characteristic sulfation absorption peaks at 820 cm^-1.D-glucose-1,4 glycosidic bonds are found in the structures of PCPP-11,Ac-PCPP-11,and S-PCPP-11.Ac-PCPP-11 is the methyl group in the acetyl group’s hydrogen signal atδ_H1.91 ppm,the carbonyl carbon signal atδ_C181.54 ppm,and the methyl carbon signal atδ_C23.34 ppm.The peaks of the S-PCPP-11proton and¹³C signals are reduced,the C3 chemical shift migrates toδ_C73.44 ppm in the low field,the absence atδ_H3.55 ppm may be caused by-SO₃,and the C2 and C4 chemical shifts migrate toδ_C68.25 ppm andδ_C76.42 ppm in the high field,indicating successful sulfation modification,respectively;PCPP-11 has a smooth and raised sheet-like morphology,Ac-PCPP-11 has an irregular,rough,and porous morphology,and the structure of S-PCPP-11becomes dispersed,presenting a smooth-surfaced block with numerous voids.（3）PCPP-11,Ac-PCPP-11,and S-PCPP-11 in vitro antioxidant and hypoglycemic activities were assessed using·OH,DPPH·,ABTS⁺·and·O₂^-scavenging ability,as well as-glucosidase and-amylase inhibition rates.The findings indicate that:The·OH scavenging ability of S-PCPP-11 was greater than that of Ac-PCPP-11,whereas the DPPH·,ABTS⁺·and·O₂^-scavenging abilities of S-PCPP-11 were less.The inhibition of-glucosidase and-amylase by S-PCPP-11 was greater than that of Ac-PCPP-11.