Estudo químico das algas pardas Lobophora variegata, Dictyota menstrualis, Dictyota mertensii e investigação farmacológica dos compostos isolados

Abstract

In this work, the extracts from the algae Lobophora variegata, Dictyota menstrualis and Dictyota mertensii (Phaeophyceae, Dictyotaceae) were investigated, resulting in the isolation of twenty-two compounds. From Dictyota species were isolated diterpenes of different skeletons such as prenilated guaiane and cadinane, crenulidane and dollabelane. Among these compounds, four have been described for the first time. From L. variegata were isolated long-chain alcohol and epoxide, two of which are new compounds. The compounds were isolated using classic methods of chromatography including chromatography on silica gel, sephadex LH-20 and high performance liquid chromatography. The structure elucidation of compounds was performed by spectroscopic methods such as: mass spectrometry (HRESIMS, APCI and GC-MS) and nuclear magnetic resonance (1H and 13C NMR) including bidimensional techniques (COSY, HSQC e HMBC), and comparison with literature data. The isolated compounds were evaluated for their cytotoxicity against the cancer cell line (HCT-116 and RAW-264.7), antimicrobial properties against Gram-positive (S. aureus ATCC 6538P) and Gram-negative (E. coli ATCC 10536) bacteria strains, antioxidant (DPPH) and anti-inflammatory effects. The long-chain epoxides designated as epoxy-lobophorenes A and B (isolated of L. variegata) showed anti-inflammatory and antioxidant effects, while the diterpenes designated dictyols K, M, N and O (isolated of D. menstrualis) showed anti-inflammatory activity comparable to dexamethasone, a potent anti-inflammatory drug in clinical use.