Geography and seasonality as factors affecting lipid classes and anti-inflammatory activity of Rugulopteryx okamurae, an invasive seaweed in Southwest Europe

Rugulopteryx okamurae is an invasive brown seaweed originating in the Pacific Ocean that has spread to Southwestern European shores in the last decade, reaching high densities and causing large ecological and economic impacts. The lipid classes and anti-inflammatory activity of this seaweed species was investigated, comprising an analysis of different geographical locations in the Mediterranean Sea and Atlantic Ocean as well as winter and summer as growing seasons. The fatty acid (FA) composition of the biomass, main lipid classes, and cyclooxygenase-2 (COX-2) inhibition were analysed. There is evidence supporting a possible class-level lipid distribution pattern specific to R. okamurae , differentiating it from other brown seaweeds. The FA profile revealed prevalence of palmitic acid and saturated FA (SFA) in all lipid classes. Lipid class distribution in R. okamurae was characterized by a majority of polar lipids, with non-polar lipids making up to 40% of the total lipid content. Within polar lipids, glycolipids were the main class and monogalactosyldiacylglycerols (MGDG) had a share ranging from 45 to 58% of the total lipids. The SFA content between 30.8 ± 1.3% (of total FA) in Atlantic (Algarve) R. okamurae MGDG and 82.5 ± 2.6% in Atlantic R. okamurae phospholipids. The FA profiles of R. okamurae from the two studied locations were quite similar, differing in palmitic acid content in triacylglycerols (TAG), oleic acid in MGDG, PUFA in digalactosyl diacylglycerols (DGDG), and n-3/n-6 ratio in MGDG. Regarding this latter parameter, the highest n-3/n-6 ratio was in Algarve MGDG samples, 1.8 ± 0.1. The preliminary screening of anti-inflammatory activity by the COX-2 assay showed higher levels of this parameter in summer R. okamurae (76.3 and 78.5% COX-2 inhibition). Therefore, R. okamurae exhibits distinctive traits and there is valorization potential by component isolation (e.g. MGDG) and further refining of biologically active fractions (e.g. anti-inflammatory ethanol extracts). • R. okamurae had more polar than non-polar lipids, making up to 40% of total lipids. • Monogalactosyldiacylglycerols were 45–58% of total lipids. • The n-3/n-6 ratio was the highest in Algarve monogalactosyldiacylglycerols. • R. okamurae lipids were extensively studied, enabling to establish a lipid profile. • Summer seaweed extracts had higher cyclooxygenase-2 inhibition, 76–79%.