Potential of microalga Isochrysis galbana: Bioactivity and bioaccessibility

The lipid composition and anti-inflammatory activity of the microalga Isochrysis galbana were studied. Moreover, the influence of bioaccessibility on composition and bioactivity was evaluated through the application of an in vitro model of the human digestion. The fatty acid (FA) profile was characterized by abundance of polyunsaturated FA (PUFA) and, within PUFA, ω3 PUFA were the most abundant. High contents of myristic, oleic, linoleic, α-linolenic, and stearidonic acids as well as docosahexaenoic acid (DHA) were determined. A low level of hydrolysis of triacylglycerols (TAGs) and polar lipids was observed during digestion. Total lipid bioaccessibility and specific FA bioaccessibility were low (between 7 and 15%). The highest bioaccessibility percentages were determined for palmitic, oleic, and linoleic acids as well as total ω6 PUFA and the lowest bioaccessible percentages were calculated for myristic and stearidonic acids, DHA, and total ω3 PUFA. Chemical affinity phenomena could be an explanation for these results. Regarding anti-inflammatory activity, it was only detected in the lipid extract of I. galbana prior to digestion (79 ± 7% of cyclooxygenase-2, COX-2, inhibition). No activity was found in the bioaccessible fraction extract. Apparently, the COX-2 inhibitory compounds were not rendered bioaccessible.