IMAO-A activity from Elaphoglossum erinaceum extracts obtained by SFE, and the isolation of prenylated acylphloroglucinols

The occurrence of phloroglucinols is restricted to ferns to which the genera Elaphoglossum and Dryopteris belong. Phloroglucinols display interesting biological activities such as antidepressant, as has been reported for hyperforin. The aim of the present study is the identification of new sources of phloroglucinols from ferns. The hexanic extract from rhizomes of E. erinaceum displayed an IC₅₀ of 105.4±2µg/ml for the MAO-A isoform. In order to have a more simplified extract, an enriched fraction containing phloroglucinol compounds was obtained by supercritical fluid extraction (SFE). For this process, 100g of material were extracted with CO₂ at 40°C using a pressure gradient of 90–300 bars, affording a colored orange crude extract. The HPLC purification on a C-18 column resulted in the isolation of four peaks, which were collected by the technique of heart cutting, and independently reinjected in the apparatus operating in the recycle mode to achieve total homogeneity after consecutive cycles. As preliminary results, the ¹H NMR spectra from a purified compound indicated the dimeric structure of a prenylated acylphloroglucinol with characteristic signals for the -OH protons at δ 18.4, 16.1, 12.9 and 10.1, as well as the signals at δ 4.47 (br. t) and 4.76 (br. s) corresponding to the preny group. Thanks to CONACYT (Mexico) and CNPq (Brazil) to support the bilateral program approved for 2009–2012, and CONACYT project N° 80980 and 156276.