Profiling phlorotannins in brown Macroalgae by liquid chromatography-high resolution mass spectronmetry

Introduction \u2013 Phlorotannins, phenolic compounds produced exclusively by Phaeophyceae (brown algae), have recently been associated with a wide variety of bene\ufb01cial bioactivities. Several studies have measured the total phenolic content in extracts from various species, but little characterisation of individual phlorotannin components has been demonstrated. Objective \u2013 The purpose of this study was to develop a liquid chromatography\u2013mass spectrometry (LC-MS) based method for rapid pro\ufb01ling of phlorotannins in brown algae. Methodology \u2013 Phlorotannin-enriched extracts from \ufb01ve phaeophyceaen species were analysed by ultrahigh-pressure liquid chromatography (UHPLC) operating in hydrophilic interaction liquid chromatography (HILIC) mode combined with high resolution mass spectrometry (HRMS). The method was optimised using an extract of Fucus vesiculosus; separation was achieved in less than 15 min. The basic mobile phase enhanced negative-ion electrospray ionisation (ESI), and generated multiply charged ions that allowed detection of high molecular weight phlorotannins. Results \u2013 The phlorotannin pro\ufb01les of Pelvetia canaliculata, Fucus spiralis, F. vesiculosus, Ascophyllum nodosum and Saccharina longicruris differed signi\ufb01cantly. Fucus vesiculosus yielded a high abundance of low molecular weight (< 1200 Da) phlorotannins, while P. canaliculata exhibited a more evenly distributed pro\ufb01le, with moderate degrees of polymerisation ranging from 3 to 49. HRMS enabled the identi\ufb01cation of phlorotannins with masses up to 6000 Da using a combination of accurate mass and \ub9\ub3C isotopic patterns. Conclusion \u2013 The UHPLC-HRMS method described was successful in rapidly pro\ufb01ling phlorotannins in brown seaweeds based on their degree of polymerisation. HILIC was demonstrated to be an effective separation mode, particularly for low molecular weight phlorotannins.Peer reviewed: YesNRC publication: Ye

Pancreatic lipase inhibitory activity of monogalactosyldiacylglycerols isolated from the freshwater microalga Chlorella sorokiniana

Chemical investigation of the freshwater microalga Chlorella sorokiniana led to the isolation of a monogalactosyldiacylglycerol (MGDG)-rich fraction possessing dose-dependent inhibitory activity against pancreatic lipase activity. The MGDG-rich fraction contains 12 MGDGs identified by LC/HRMS analysis. Among them, three MGDGs were new compounds, namely, (2S)-1-O-(7Z,10Z-hexadecadienoyl)-2-O-(7Z,10Z,13Z-hexadecatrienoyl)-3-O-\u3b2-D-galactopyranosylglycerol (1), (2S)-1-O-linoleoyl-2-O-(7Z,10Z-hexadecadienoyl)-3-O-\u3b2-D-galactopyranosylglycerol (6), and (2S)-1-O-oleoyl-2-O-(7Z,10Z-hexadecadienoyl)-3-O-\u3b2-D-galactopyranosylglycerol (8). The major galactolipids were isolated by semipreparative HPLC and tested for their effect toward pancreatic lipase inhibitory activity. All the tested MGDGs showed significant reduction of pancreatic lipase activity indicating possible beneficial use for management of lipase-related disorders such as obesity.Peer reviewed: YesNRC publication: Ye