Department of Earth and Environmental Sciences, University of Pavia, 27100 Pavia, Italy.
Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy.
Molecules. 2021 Jan 16;26(2):455. doi: 10.3390/molecules26020455.
During the years, many usnic acid (UA) conjugates have been synthesized to obtain potent endowed with biological properties. Since ()-UA is less abundant in nature than ()-enantiomer, it is difficult to source, thus precluding a deeper investigation. Among the lichens producing UA, is a valuable (S)-UA source. In the present work, we report on a rapid HPLC-UV/PAD-CD protocol suitable for the analysis and the identification of the main secondary metabolites present in extract. Best results were achieved using XBridge Phenyl column and acetonitrile and water, which were both added with formic acid as mobile phase in gradient elution. By combining analytical, spectroscopical, and chiroptical analysis, the most abundant analyte was unambiguously identified as ()-UA. Accordingly, a versatile microwave-assisted extractive (MAE) protocol, assisted by a design of experiment (DoE), to quantitatively recover ()-UA was set up. The best result in terms of UA extraction yield was obtained using ethanol and heating at 80 °C under microwave irradiation for 5 min. Starting from 100 g of dried , 420 mg of ()-UA were achieved. Thus, our extraction method resulted in a suitable protocol to produce ()-UA from for biological and pharmaceutical investigation or commercial purposes.
多年来，人们已经合成了许多乌头酸（UA）缀合物，以获得具有生物特性的有效物质。由于（）-UA 在自然界中的丰度低于（）-对映异构体，因此难以获得，从而限制了对其更深入的研究。在产生 UA 的地衣中，是（S）-UA 的有价值来源。在本工作中，我们报告了一种快速 HPLC-UV/PAD-CD 方案，适用于分析和鉴定 提取物中主要次生代谢物的存在。使用 XBridge Phenyl 柱和乙腈和水，并在梯度洗脱中添加甲酸作为流动相，可获得最佳结果。通过结合分析、光谱和手性分析，明确鉴定出最丰富的分析物为（）-UA。因此，建立了一种多功能的微波辅助提取（MAE）方案，通过实验设计（DoE）辅助，以定量回收（）-UA。在微波辐射下用乙醇加热至 80°C 5 分钟，可获得最佳的 UA 提取产率。从 100 g 干燥的开始，可获得 420 mg 的（）-UA。因此，我们的提取方法为从 进行生物和药物研究或商业目的生产（）-UA 提供了一种合适的方案。
