Drying Peppermint Medicinal plant (Mentha piperita) using Combinations of Shade and Microwave Treatments –Part Two: Investigating the Effects of Treatments on some Phytochemical Properties of Dried Leaves

Drying is the most common way to preserve medicinal plants and protect their biochemical compounds. In order to investigate the effect of different drying methods on some phytochemical properties of Mentha piperitae, including the content of total phenolics, total flavonoids, flavon and flavonol, and also antioxidant activity and total carbohydrates, two experiments were conducted separately based on a completely randomized design with three repetitions. The results showed a significant effect of different drying methods on the studied traits (p<0.05). In simple drying, the maximum amount of total phenolics, total flavonoid, flavone and flavonols related to fresh sample, while the minimum amount of these compounds was obtained in oven treatment with a temperature of 70oC, but in the combined drying method, the maximum amount of total phenolics, total flavonoid and flavon and flavonol were found in the combination treatment of shade + microwave 450 W, and the minimum amount was observed in the microwave drying method of 100 W + shade. Also, in the simple drying method, samples dried in artificial shade with 88.83% and in combined drying with treatment shade + 450 W microwave with 0.48% had the maximum antioxidant activity. Therefore, it can be concluded that in the simple drying of the fresh sample and in the combined drying of the shade + 450 W microwave method, they will be very favorable because they will maintain the biochemical characteristics.