IntroductionThe safety and quality of many medicinally important herbs are compromised since farmers and small organizations are involved in the cultivation, aggregation, and primary processing of these herbs. Such organizations often lack adequate quality control facilities. To improve the safety and quality of herbal products, simple, rapid, and affordable quality control systems are required.ObjectivesThe aim of this study was to assess the suitability of microwave oven‐drying for moisture content (MC) determination and sample preparation of herbs in small organizations.MethodsMicrowave oven‐drying (720 W) and convective oven‐drying at 105°C for MC determination were compared. The effects of three different drying methods (microwave oven‐drying, low‐temperature convective drying, and freeze‐drying) on in vitro antioxidant and polyphenol oxidase (PPO) activity were determined, similarity analysis was conducted using HPLC signature spectra, and validation was performed with LC‐MS focusing on one herb.ResultsMicrowave oven‐drying at 720 W significantly reduced the drying time (from hours to minutes), whereas the spatial variation of temperature in convective ovens set at 105°C can cause about 10% underestimation of MC. Microwave oven‐drying showed similar macro‐properties like freeze‐drying and higher extractability (10%–20%) and in vitro antioxidant capacity (33%–66%) and lower PPO activity compared to low‐temperature convective drying. HPLC signature spectra revealed strong similarity of soluble components between freeze‐dried and microwave oven‐dried herbs. LC‐MS analysis demonstrated more common compounds between freeze‐dried and microwave oven‐dried Centella asiatica extracts, whereas convective tray‐dried samples had fewer compounds common with samples obtained by freeze‐drying or microwave oven‐drying.ConclusionsMicrowave oven‐drying is rapid (tens of min) and shows small batch‐to‐batch variation compared to oven‐drying at 105°C. The in vitro antioxidant assays and signature spectra can be used for assessing the source and purity or quality of a specific herb variety.

中文翻译：

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微波干燥评估以快速方便地分析药用植物以保证质量

简介由于农民和小型组织参与了这些药草的种植、聚集和初级加工，因此许多药用重要药草的安全和质量受到影响。此类组织往往缺乏足够的质量控制设施。为了提高草药产品的安全性和质量，需要简单、快速且经济实惠的质量控制系统。 目的本研究的目的是评估微波炉干燥对草药中水分含量 (MC) 测定和样品制备的适用性。方法对用于 MC 测定的微波炉干燥（720 W）和 105°C 对流烤箱干燥进行比较。三种不同干燥方法（微波炉干燥、低温对流干燥、冷冻干燥）对干燥效果的影响体外测定抗氧化剂和多酚氧化酶 (PPO) 活性，使用 HPLC 特征谱进行相似性分析，并使用 LC-MS 对一种草药进行验证。结果 720 W 的微波炉干燥显着缩短了干燥时间（从几小时缩短到几分钟） ），而设置为 105°C 的对流烤箱中温度的空间变化可能会导致 MC 被低估约 10%。微波炉干燥表现出与冷冻干燥相似的宏观特性和更高的可提取性（10%–20%）体外与低温对流干燥相比，抗氧化能力（33%–66%）和较低的 PPO 活性。HPLC 特征光谱揭晓强的相似的冷冻干燥和微波炉干燥草药之间的可溶性成分。LC-MS 分析表明冷冻干燥和微波炉干燥之间存在更常见的化合物积雪草提取物，而对流托盘干燥样品中的化合物与通过冷冻干燥或微波炉干燥获得的样品中常见的化合物较少。结论微波炉干燥速度快（数十分钟），并且与烤箱干燥相比，批次间差异较小在105°C。这体外抗氧化剂测定和特征光谱可用于评估特定草药品种的来源和纯度或质量。