Effects of Drying and Extraction Conditions on the Biochemical Activity of Selected Herbs

Herbs have been long known to provide health-promoting benefits and are demonstrated to have antioxidant, anti-inflammatory, antibacterial, analgesic, and antitumor activities. This study evaluated the effects of drying conditions and extraction protocols on the biochemical activity of three culinary and medicinal herbs: rosemary (Rosmarinus officinalis), motherwort (Leonurus cardiaca), and peppermint (Mentha piperita). Leaf tissues were dried by sun, oven-dried at 40 8C, or oven-dried at 70 8C and extracted using 80% methanol or 80% ethanol. Total polyphenol (TPP) using the Folin- Ciocalteu reagent method and antioxidant capacity using the Trolox-equivalent antiox- idant capacity (TEAC) assay were determined. Both drying and extraction conditions significantly impacted TPP content and TEAC in the three herb species. Sun-dried or 40 8C oven-dried herbs exhibited significantly higher TPP content and TEAC capacity than fresh samples, suggesting low-temperature drying may bea goodpostharvest means to store medicinal/culinary herbs. Exposure to 70 8C oven-drying caused significant antioxidant loss. In addition, the current study showed that with fresh tissue, 80% ethanol extraction had significantly higher TPP and TEAC than 80% methanol extraction for all three herbs, yet for dried herbs, the efficacy of ethanol/methanol extraction varied with different drying treatments.