Abstract
Alpinia zerumbet (Zingiberaceae) is an important medicinal plant found in several countries and used in folk medicine. The hypotensive and anxiolytic effects of the preparations made from this plant are mainly attributed to flavonoids and kavalactones, respectively. The aim of this study was to compare infusions, hydroalcohol extracts and tinctures obtained with fresh and dried leaves of A. zerumbet collected in two Brazilian cities: Rio de Janeiro/RJ and Brasilia/DF. Colorimetric methods were used to evaluate the antioxidant activity, total phenolic and total flavonoid contents of the extracts. The flavonoids and dihydro-5,6-dehydrokavain (DDK) contents were analyzed by HPLC-DAD and the volatile compounds were evaluated by headspace solid phase extraction (SPE) followed by GC–MS analyses, which also evaluated the nonpolar fractions. The fresh and dried leaves from both Brazilian cities contain high amounts of flavonoids with antioxidant activity. The 80 % hydroalcohol extract prepared with fresh leaves collected in Brasilia exhibited the highest antioxidant activity by the phosphomolybdenum and DPPH methods. HPLC analyses of the infusions prepared with fresh leaves collected in Rio de Janeiro showed the highest DDK content, 6.63 mg/g of the extract. The GC–MS analyses of the nonpolar fractions from the aqueous extracts, from both cities, showed the presence of two major substances, the kavalactones DDK and 5,6-dehydrokavain. The evaluation of the loss of volatile substances by headspace SPE showed that even after a storage time of 30 days, there were still volatile substances in the dried plant material from both cities. In addition, the loss of terpinen-4-ol and γ-terpinene from the fresh leaves was very low, showing the slow release of these substances under the studied conditions. In conclusion, this work shows that the chemical standardization of A. zerumbet preparations contains terpenoids, kavalactones and phenolic compounds related to the biological activities which are important to corroborate the different uses of this species.
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