成熟度对桑椹果实多糖与酚类的影响

Effects of ripeness on polysaccharides and phenols in Morus alba fruit

目的研究桑椹果实在生长成熟过程中基础营养成分以及多糖、酚类成分的变化。方法采用木里氏纤维素酶、α-淀粉酶和木瓜蛋白酶混合作用提取桑椹中的多糖,采用离子色谱法检测单糖组成,采用尺寸排阻色谱与多角度光散射联用与示差折光检测器联用技术检测桑椹多糖的分子量,采用傅里叶红外光谱和原子力显微镜检测多糖的结构组成和形态;桑椹酚类物质通过甲醇提取、旋蒸、树脂纯化、旋蒸和冻干,采用液相色谱-质谱检测其中酚类组成及含量比例。结果桑椹果实的含水量在青、红果时为89.49%和90.55%,成熟后略微下降至86.90%;灰分在成熟过程中下降明显,从1.09%逐渐下降至0.64%、0.48%;可溶性固形物,即主要是可溶性糖含量从青果的7.11%和红果的7.05%最终上升至成熟果的12.29%。随着桑椹成熟度升高,桑椹多糖组成中葡萄糖含量占比由20.04%下降至11.36%和5.11%,半乳糖醛酸含量占比由26.32%上升至41.85%和45.77%,多糖分子量变小。3种不同成熟度桑椹多糖均鉴定为果胶型多糖,主要成分为半乳糖醛酸;酚类主要由绿原酸、绿原酸二聚体、芦丁、槲皮素、矢车菊素-3-葡萄糖苷和矢车菊素-3-芸香糖苷等组成。结论成熟桑椹中营养成分高于未成熟桑椹,特别是其中可溶性固形物及花色苷含量,其中花色苷会随着桑椹成熟发生大幅的升高,而桑椹多糖为果胶多糖,随着成熟其同型半乳糖醛酸聚糖与鼠李半乳糖醛酸聚糖I结构域占比增加,为链状或球状结构。

Objective To elucidate the alterations in the fundamental nutritional components,as well as polysaccharide and phenolic constituents,during the maturation process of Morus alba fruits.Methods The extraction of Morus alba’polysaccharides was achieved through the combined action of Murashige cellulase,α-amylase,and papain.Monosaccharide composition was determined using ion chromatography.The molecular weight of Morus alba polysaccharides was ascertained through size exclusion chromatography coupled with multi-angle light scattering and refractive index detection techniques.Fourier transform infrared spectroscopy and atomic force microscopy were employed to analyze the structural composition and morphology of the polysaccharides.Phenolic substances in Morus alba were extracted with methanol,concentrated by rotary evaporation,purified using resin,and subsequently lyophilized.The phenolic composition and content were quantified using liquid chromatography-mass spectrometry.Results The water content of Morus alba fruit was 89.49%and 90.55%in green and red fruits,and decreased slightly to 86.90%after ripening,and the ash content decreased significantly in the ripening process,gradually decreasing from 1.09%to 0.64%and 0.48%,and the soluble solids,that is,mainly soluble sugars,increased from 7.11%in green fruits and 7.05%in red fruits to 12.29%in mature fruits.With the increase of Morus alba maturity,the proportion of glucose content decreased from 20.04%to 11.36%and 5.11%,the proportion of galacturonic acid content increased from 26.32%to 41.85%and 45.77%,and the molecular weight of polysaccharides decreased.Polysaccharides from Morus alba at 3 kinds of different maturity stages were all identified as pectic polysaccharides,primarily comprising galacturonic acid.The phenolic composition was predominantly constituted of chlorogenic acid,chlorogenic acid dimers,rutin,quercetin,cyanidin-3-glucoside,and cyanidin-3-rutinoside.Conclusion The nutritional components in mature Morus alba are higher than those in immature Morus alba,especially the content of soluble solids and anthocyanins,in which anthocyanins will increase greatly with the maturity of Morus alba,while Morus alba polysaccharide is pectin polysaccharide,and the proportion of homogalacturonan and rhamnolian I domain increases with the maturity,which is chain or spherical structure.