Drying methods affect the extracts and essential oil of Mentha aquatica L

Abstract

Drying is the most appropriate method used for the preservation of natural products of plants. The selection of a specific drying method represents one important expense in the production and commercialisation of medicinal plants. This study determined the effect of different drying methods (shade drying (SD) at 30 °C, oven-drying (OV) at 50 °C and microwave (MW) with 300 and 600 W) on mint. The measurement of phytochemical and antibacterial activity of the essential oil (EO) and the extracts were studied in all fresh plants (FP) and dried plants. Results showed that SD and OV had the highest yield of EO. The best quercetin level was obtained with OV at 50 °C. The highest total polyphenols was seen for the extract with FP while the highest total flavonoids and tannins was found in dried plants. The highest antioxidant potential for the EO was shown with OV and for the extract with the MW at 600 W. The highest antibacterial activity was observed with EO for all drying methods against E. coli, S. aureus and Salmonella. On the other hand, only the extract of dried mint at 600 W had an antibacterial activity against these bacteria. Drying mint in an oven at 50 °C was the best method to obtain the EO, and 600 W gave the most appropriate methods to obtain the best extract.