莲房原花色素的纯化分级和结构鉴定

Purification, Fractionation and Identification of Proanthocyanidins from Lotus (Nelumbo nucifera Gaertn.) Seedpods

莲房中原花色素经甲醇水提取,大孔树脂纯化,制得莲房原花色素提取物(LSPE),酸降解法测定其平均聚合度,并经TSK HW-40s凝胶树脂分级,高效液相色谱-二极管阵列检测器和电喷雾质谱分析。结果表明:采用60%甲醇水溶液,调整pH值至2.0,料液比1:20(m/V),在60℃提取1h,提取率可达7.65%,最适合纯化的树脂为AB-8。LSPE乙酸乙酯相和水相平均聚合度为3.2和15.4。LSPE乙酸乙酯相主要由儿茶素、没食子酸儿茶素、儿茶素和没食子酸儿茶素构成的二聚体、三聚体和少量四聚体构成。凝胶树脂将LSPE乙酸乙酯相分为11个级分(F1～F11),F1～F4可能为黄酮类及黄酮苷类,F5主要为儿茶素以及少量表儿茶素,F6为没食子酸儿茶素、原花青素二聚体B3、儿茶素,以及含有没食子酸儿茶素单元的原花色素,F7为儿茶素和原花青素B1、B2、B3,F8为原花色素类物质,F9～F11可能为儿茶素和没食子酸儿茶素组成的更高聚合度的聚合物。

Lotus proanthocyanidin extract （LSPE） from lotus seedpods was prepared through extraction with aqueous methanol and purification by macroporous resin adsorption. Average degree of polymerization of LSPE was measured by means of acid degradation. Moreover, it was fractionated using TSK HW-40s resin and analyzed by high performance liquid chromatography （HPLC） with diode array detection and electrospray ionization-mass spectrometry （ESI-MS）. The results showed that the extraction yield of proanthocyanidins was 7.65% after 1 h extraction at 60 ℃ with 60% aqueous methanol solution acidified to pH 2.0 at a solid-to-solvent ratio of 1：20 （m/V）. AB-8 resin was the most suitable for LSPE purification among three types marcroporous resin investigated. The average degree of polymerization of LSPE was 3.2 in the ethyl acetate phase and 15.4 in the water phase. The ethyl acetate-soluble fraction of LSPE mainly comprised catechin, gallocatechin, and their dimers, trimers and tetramers in small quantities. This fraction was further fractionated by TSK HW-40s resin chromatography into 11 sub-fractions （F1-F11）. F1, F2, F3 and F4 might be flavonoids or flavonoid glycosides, F5 was mainly composed of catechin and a small amount of epicatechin, F6 was made up of gallocatechin, catechin, procyanidins dimmer B3 and proanthocyanidins containing gallocatechin units, F7 consisted of catechin, procyanidins dimmers B1, B2 and B3, F8 comprised proanthocyanidins, and F9, F10 and F11 was likely to be polymers with higher degree of polymerization consisting of catechin and gallocatechin.