Effects of Drying and Extraction Conditions On the Biochemical and Biological Activity of Selected Herbs

Herbs and spices have not only been used as food preservatives and flavoring, but have also been used as traditional medicines for thousands of years.  Scientific evidence increasingly supports the potential health benefits of herbs with plant extracts displaying antioxidant, anti-inflammatory, antibacterial, analgesic, and antitumor activities. 

Chemical and biological activities of medicinal plants depend on many factors, such growth environment, harvesting time, and storage and drying condition.  The objectives of this study were to evaluate the effects of extraction protocols and drying conditions on biochemical and biological activity of selected herbs.  Four culinary and medicinal herbs: sage (Salvia officinalis), rosemary (Rosmarinus officinalis), peppermint (Mentha piperita), and common motherwort (Leonurus cardiaca) were dried at room temperature, 40 ^oC, or 70 ^oC.  Extraction was conducted using 80% methanol or 80% ethanol.  Total polyphenol was measured according to the Folin-Ciocalteu reagent method.  Antioxidant capacity was determined with the Trolox-equivalent antioxidant capacity (TEAC) assay.  The results showed both the drying conditions and extraction conditions could impact the total polyphenolic content and antioxidant capacity.  In peppermint, 40 ^oC oven drying resulted in the highest antioxidant capacity level among all of the treatments when extraction was conducted using 80% methanol.  When extraction was conducted using 80% ethanol, room temperature drying generated the highest antioxidant capacity level.  The total polyphenol content and antioxidant capacity also varied with different herb species.  The inhibitory effects of these herb extracts to cancer cell growth were also evaluated and will be discussed.