Development of new efficient method for isolation of phenolics from sea algae prior to their rapid resolution liquid chromatographic-tandem mass spectrometric determination

The extraction of phenolic compounds from 4 different sea algae samples, three brown algae (Cystoseira abies-marina, C. abies-marina grinded under cryogenic conditions with liquid nitrogen, Undaria pinnatifida and Sargassum muticum) and one red algae (Chondrus crispus) via solid phase extraction using micro-elution solid-phase extraction (μ-SPE) plate method was studied. Prior to μ-SPE, 50 mg of algae with 80% methanol mixture was extracted in hyphenated series by various extraction techniques, such as pressurized liquid extraction and Ika Ultra-Turrax® Tube Drive, in combination with ultrasound assisted extraction. The μ-SPE plate technique reduced the time of sample pre-treatment thanks to higher sensitivity and pre-concentration effect. Selected groups of benzoic acid derivatives (p-hydroxybenzoic, protocatechuic, gallic, vanillic, and syringic acids), hydroxybenzaldehydes (4-hydroxybenzaldehyde, and 3,4-dihydroxybenzaldehyde), and cinnamic acid derivatives (p-coumaric, caffeic, ferulic, sinapic, and chlorogenic acids) were determined using rapid resolution liquid chromatography coupled to mass spectrometry detection with negative ion electrospray ionization (RRLC-ESI-MS) using multiple reactions monitoring. LOQs of measured samples varied in the range 0.23-1.68 ng/mL and LODs in the range 0.07-0.52 ng/mL. The applied method allowed a simultaneous determination of phenolics (i.e. free, esters soluble in methanol, glycosides, and esters insoluble in methanol) in less than 5 min (including alkaline or acidic hydrolysis of raw extracts) from sea algae extracts.