Equisetum hyemale L.: phenolic compounds, flavonoids and antioxidant activity

In the postharvest process and subsequent commercialization of the vegetal drug (dry plant), the drying and storage are of fundamental importance for obtaining a phytotherapic agent. In Brazil, most plants are commercialized “in natura” or dried inadequately. Among these species whose use reflects a cultural fad, marketing associated with false claims, and consequently irrational use by the population is Equisetum hyemale L., known as horsetail and employed for fast weight loss and suppression of appetite. Thus, the aim of this study was to evaluate the conservation of bioactive compounds of E. hyemale (dried plant) in relation to natural drying (sun drying, SDE and thin layer drying, TLE) and artificial drying process (conventional oven drying, COE). Dry plant obtained from aerial parts of E. hyemale was evaluated in relation to the extract yield of phenolic compounds, flavonoids and antioxidant activity and compared to the fresh aerial parts extract (APE). The highest phenolic and flavonoid contents were in TLE, which were 38.70 and 65.65% lower than in APE (193.1037 and 37.3963 g 100 g^‑1 dry mass, respectively). In E. hyemale, the effectiveness of the drying processes when compared with extract from fresh plant allowed us to conclude that although TLE has higher contents of phenolic compounds and flavonoids, this process was less efficient in the conservation of the antioxidant activity and that COE was a better approach to preserve antioxidants.