Gbashi Sefater, Njobeh Patrick, Steenkamp Paul, Tutu Hlanganani, Madala Ntakadzeni
Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Doornfontein Campus, P.O. Box 17011, Johannesburg, Gauteng, 2028, South Africa.
Department of Biochemistry, University of Johannesburg, P.O. Box 524, Auckland Park, Johannesburg, 2006, South Africa.
Chem Cent J. 2016 Jun 8;10(1):37. doi: 10.1186/s13065-016-0182-z.
Pressurized hot water extraction (PHWE) technique has recently gain much attention for the extraction of biologically active compounds from plant tissues for analytical purposes, due to the limited use of organic solvents, its cost-effectiveness, ease-of-use and efficiency. An increase in temperature results in higher yields, however, issues with degradation of some metabolites (e.g. tartrate esters) when PHWE is conditioned at elevated temperatures has greatly limited its use. In this study, we considered possibilities of optimizing PHWE of some specific functional metabolites from Bidens pilosa using solvent compositions of 0, 20, 40 and 60 % methanol and a temperature profile of 50, 100 and 150 °C.
The extracts obtained were analyzed using UPLC-qTOF-MS/MS and the results showed that both temperature and solvent composition were critical for efficient recovery of target metabolites, i.e., dicaffeoylquinic acid (diCQA) and chicoric acid (CA), which are known to possess anti-HIV properties. It was also possible to extract different isomers (possibly cis-geometrical isomers) of these molecules. Significantly differential (p ≤ 0.05) recovery patterns corresponding to the extraction conditions were observed as recovery increased with increase in methanol composition as well as temperature. The major compounds recovered in descending order were 3,5-diCQA with relative peak intensity of 204.23 ± 3.16 extracted at 50 °C and 60 % methanol; chicoric acid (141.00 ± 3.55) at 50 °C and 60 % methanol; 4,5-diCQA (108.05 ± 4.76) at 150 °C and 0 % methanol; 3,4-diCQA (53.04 ± 13.49) at 150 °C and 0 % methanol; chicoric acid isomer (40.01 ± 1.14) at 150 °C and 20 % methanol; and cis-3,5-diCQA (12.07 ± 5.54) at 100 °C and 60 % methanol. Fitting the central composite design response surface model to our data generated models that fit the data well with R values ranging from 0.57 to 0.87. Accordingly, it was possible to observe on the response surface plots the effects of temperature and solvent composition on the recovery patterns of these metabolites as well as to establish the optimum extraction conditions. Furthermore, the pareto charts revealed that methanol composition had a stronger effect on extraction yield than temperature.
Using methanol as a co-solvent resulted in significantly higher (p ≤ 0.05) even at temperatures as low as 50 °C, thus undermining the limitation of thermal degradation at higher temperatures during PHWE.
由于有机溶剂使用受限、成本效益高、易于操作且效率高，加压热水萃取（PHWE）技术最近在从植物组织中提取生物活性化合物用于分析目的方面备受关注。温度升高会带来更高的产量，然而，当PHWE在高温条件下进行时，一些代谢物（如酒石酸酯）的降解问题极大地限制了其应用。在本研究中，我们考虑了使用0%、20%、40%和60%甲醇的溶剂组成以及50℃、100℃和150℃的温度曲线来优化从鬼针草中提取某些特定功能代谢物的PHWE的可能性。
使用超高效液相色谱-四极杆飞行时间串联质谱（UPLC-qTOF-MS/MS）对所得提取物进行分析，结果表明温度和溶剂组成对于有效回收目标代谢物至关重要，即二咖啡酰奎宁酸（diCQA）和菊苣酸（CA），已知它们具有抗HIV特性。还能够提取这些分子的不同异构体（可能是顺式几何异构体）。随着甲醇组成和温度的增加，回收率也随之增加，观察到与提取条件相对应的显著差异（p≤0.05）的回收模式。回收的主要化合物按降序排列为：在50℃和60%甲醇条件下提取的相对峰强度为204.23±3.16的3,5-diCQA；在50℃和60%甲醇条件下的菊苣酸（141.00±3.55）；在150℃和0%甲醇条件下的4,5-diCQA（108.05±4.76）；在150℃和0%甲醇条件下的3,4-diCQA（53.04±13.49）；在150℃和20%甲醇条件下的菊苣酸异构体（40.01±1.14）；以及在100℃和60%甲醇条件下的顺式-3,5-diCQA（12.07±5.54）。将中心复合设计响应面模型拟合到我们的数据中，生成了与数据拟合良好的模型，R值范围为0.57至0.87。因此，有可能在响应面图上观察温度和溶剂组成对这些代谢物回收模式的影响，并确定最佳提取条件。此外，帕累托图显示甲醇组成对提取产率的影响比温度更强。
即使在低至50℃的温度下，使用甲醇作为共溶剂也能显著提高（p≤0.05）回收率，从而克服了PHWE在较高温度下热降解的局限性。
