Taghavi Toktam, Patel Hiral, Akande Omololu E, Galam Dominique Clark A
Agricultural Research Station, Virginia State University, Petersburg, VA 23806, USA.
Foods. 2022 Apr 7;11(8):1072. doi: 10.3390/foods11081072.
Anthocyanins are the primarily pigments in many flowers, vegetables, and fruits and play a critical role in human and plant health. They are polyphenolic pigments that are soluble in water and usually quantified by spectrophotometric methods. The two main methods that quantify anthocyanins are pH differential and organic solvent-based methods. Our hypothesis was that these methods extract different anthocyanin profiles. Therefore, this experiment was designed to identify anthocyanin profiles that are extracted by pH differential and organic solvent-based methods and observe their total anthocyanin content from strawberries. Six methods were tested in this experiment to quantify and profile anthocyanins in strawberry fruits by spectrophotometry and Ultra High Performance Liquid Chromatography (UHPLC) respectively. Four methods used organic solvents (methanol, and chloroform-methanol) in different combinations. The next two methods were pH differential and a combination of organic solvent and the pH differential method. The results suggest that acidified chloroform-methanol extracted the highest anthocyanin content compared to water-based solvents. Methanol-water based solvents also performed better than methanol alone, because both methanol and water may extract different profiles of anthocyanins. Water-based extracts had the greatest absorbance at a lower wavelength (498 nm), followed by methanol (508 nm), and chloroform (530 nm). Chloroform-methanol solvent with higher pH (3.0) extracted pelargonidin as the main anthocyanin, while methanol and water-based solvents (with lower pH 1.0-2.0) extracted delphinidin as their main anthocyanin as identified by UHPLC. Therefore, chloroform-methanol and methanol-water solvents were the best solvents for extracting anthocyanins from strawberries. Also, freeze-dried strawberries had higher anthocyanin contents compared to fresh or frozen samples.
花青素是许多花卉、蔬菜和水果中的主要色素，对人类和植物健康起着关键作用。它们是可溶于水的多酚类色素，通常通过分光光度法进行定量分析。定量分析花青素的两种主要方法是pH差值法和基于有机溶剂的方法。我们的假设是这些方法提取的花青素谱不同。因此，本实验旨在鉴定通过pH差值法和基于有机溶剂的方法提取的花青素谱，并观察草莓中的总花青素含量。本实验测试了六种方法，分别通过分光光度法和超高效液相色谱法（UHPLC）对草莓果实中的花青素进行定量分析和谱图分析。四种方法使用了不同组合的有机溶剂（甲醇以及氯仿 - 甲醇）。另外两种方法是pH差值法以及有机溶剂与pH差值法的组合。结果表明，与水基溶剂相比，酸化氯仿 - 甲醇提取的花青素含量最高。甲醇 - 水基溶剂的效果也优于单独使用甲醇，因为甲醇和水可能提取不同的花青素谱。水基提取物在较低波长（498nm）处吸光度最大，其次是甲醇（508nm），氯仿（530nm）。通过UHPLC鉴定，pH值较高（3.0）的氯仿 - 甲醇溶剂提取的主要花青素为天竺葵素，而甲醇和水基溶剂（pH值较低，1.0 - 2.0）提取的主要花青素为飞燕草素。因此，氯仿 - 甲醇和甲醇 - 水溶剂是从草莓中提取花青素的最佳溶剂。此外，冷冻干燥的草莓比新鲜或冷冻样品的花青素含量更高。
