Subcritical water extraction and characterization of bioactive compounds from Haematococcus pluvialis microalga

In this work, extraction and characterization of compounds with antioxidant and antimicrobial activity from Haematococcus pluvialis microalga in red phase have been carried out. To do this, subcritical water extraction (SWE) has been combined with analytical techniques such as HPLC–DAD, HPLC–QqQ-MS and GC–MS and in vitro assays (i.e., for antioxidant and antimicrobial activity). The effect of the extraction temperature (50, 100, 150 and 200 °C) and solvent polarity has been studied in terms of yield and activity of the extracts. Results demonstrate that the extraction temperature has a positive influence in the extraction yield and antioxidant activity. Thus, the extraction yield achieved with this process was higher than 30% of dry weight at 200 °C as extraction temperature. Moreover, the extract obtained at 200 °C presented the highest antioxidant activity by far, while temperature does not seem to significatively affect the antimicrobial activity. Chemical composition was determined by HPLC–DAD, HPLC–QqQ-MS and GC–MS. Short chain fatty acids turned out to be responsible of the antimicrobial activity, whereas the antioxidant activity was correlated to vitamin E (present exclusively in the 200 °C extract), together with simple phenols, caramelization products and possible Maillard reaction products obtained during the extraction at high temperatures.