Structural elucidation of pectin extracted from cocoa pod husk (Theobroma Cacao L.): Evaluation of the degree of esterification using FT-IR and 1H NMR
Structural elucidation of pectin extracted from cocoa pod husk (Theobroma Cacao L.): Evaluation of the degree of esterification using FT-IR and 1H NMR
复制标题
DOI：
10.1007/s13399-023-04082-3
复制
发表时间：
2023-04-17
影响因子：
4
通讯作者：
Cordova, Bryan M.
中科院分区：
文献类型：
--
作者：
Huamani-Palomino, Ronny G.;Ramos, M. Pedro;Cordova, Bryan M.
如今，对可可衍生物的需求日益增加，由于大量的可可豆荚壳（CPH）废物，在耕地和农场附近产生了严重的处理问题。基于此，本文以CPH为原料，采用柠檬酸法提取果胶，并利用核磁共振和红外光谱对CPH果胶进行结构表征，在红外光谱技术方面，采用衰减全反射红外光谱（ATR-IR）方法对CPH果胶与商品果胶进行了比较，同时采用二阶导数红外光谱（FT-IR）方法对CPH果胶的掩蔽谱带进行了研究。此外，通过1725 cm（-1）和1610 cm（-1）处的谱带进行去卷积处理以估计酯化度。另一方面，通过1D和2D NMR进行CPH果胶的结构解析，以验证连接到半乳糖醛酸基团的鼠李糖基团的存在，表明RG-I结构。此外，使用H-1 NMR评估酯化度，并与FT-IR方法进行比较，其显示约35-37%的相似值，并且描绘了CPH果胶中的低酯化度。此外，CPH果胶的抗氧化活性被探索达到11.79 +/-1.10%的值，与聚半乳糖醛酸（10.31 +/- 3.29）和其他基于果胶的材料的平均值相比稍高。最后，通过XRD观察到无定形结构，并且通过EDX分析丢弃果胶表面上镉的存在，而通过FESEM观察片状结构来探索形态。
Nowadays, the increasing demand for cocoa derivatives is generating a serious disposal problem in close proximity to cultivated lands and farms owing to the huge quantity of cocoa pod husk (CPH) waste. Based on this context, this paper deals with the utilization of CPH as raw material for pectin extraction using citric acid and its structural characterization by NMR and FT-IR. Regarding the FT-IR technique, pectin from CPH was compared with commercial pectin by the ATR-IR method, while the second-derivative FT-IR method was conducted to explore masked bands in the normal CPH pectin spectrum. In addition, a deconvolution process was carried out for estimating the degree of esterification through the bands at 1725 cm(-1) and 1610 cm(-1). On the other hand, structural elucidation of CPH pectin was performed by 1D and 2D NMR to validate the presence of rhamnose groups attached to galacturonic acid groups suggesting a RG-I structure. Besides, the degree of esterification was evaluated using H-1 NMR and compared with the FT-IR method, which showed similar values around 35-37% and depicted a low degree of esterification in CPH pectin. Additionally, the antioxidant activity of CPH pectin was explored reaching a value of 11.79 +/- 1.10%, a bit higher compared with the average value for polygalacturonic acid (10.31 +/- 3.29) and other pectin-based materials. Finally, an amorphous structure was observed by XRD, and also, the presence of cadmium on pectin surface was discarded by EDX analysis, whereas the morphology was explored by FESEM observing a sheet-like structure.