Feasibility of microwave drying for analysis and processing of medicinal plants

Abstract

Drying herbal products is essential for sample preparation and ensuring product quality. This study explored the efficacy of microwave-based drying (MW) as an alternative method for moisture content (MC) determination and quality preservation of herbal plants viz, Centella asiatica, Eryngium foetidum, Enhydra fluctuans and Marsilea minuta. Compared to the standard drying method (oven drying at 105°C), the microwave-based loss-on drying method demonstrated significantly more efficiency in reducing drying time and spatial distribution. The study confirms that MW has similar macro-properties and antioxidant activity to freeze-drying. Among the four herbs studied, MW had 10-20% more extractability and had high similarity (Pearson correlation coefficient <0.8 and low Euclidean distance) among soluble components. LC-MS analysis of Centella asiatica revealed that MW shared 46% common compounds while convective drying only had 27% common compounds to freeze drying. Overall, MW proved to be a faster drying process and reliable MC determination method with better retention of bioactive compounds. These findings contribute to rapid and qualitative sample preparation for analyzing both physicochemical properties and secondary metabolites of medicinal plants and herbal products. This, in turn, can positively impact the development of herbal products with improved drying techniques, meeting the growing demand for high-quality culinary and medicinal products.