Bioactivity and Chemical Profiling of the Sea-Ice Microalga Microglena antarctica (Chlorophyceae)

Antarctic algae have evolved in extreme environmental conditions, developing unique metabolic adaptations with significant biotechnological potential. In this study, we explored the bioactivity of the sea-ice microalga Microglena antarctica by preparing acetone and methanol extracts from biomass cultivated at 4, 8, and 16 °C. These extracts were screened for their in vitro antioxidant properties and inhibitory activities on enzymes related to Alzheimer's disease (acetylcholinesterase: AChE, butyrylcholinesterase: BChE), type 2 diabetes mellitus (T2DM, α-glucosidase, α-amylase), obesity (lipase), and hyperpigmentation (tyrosinase). Our screening revealed a high capacity of acetone extracts to scavenge the ABTS•⁺ radical (EC₅₀ ranging from 3.57 to 4.18 mg mL^-1), along with strong copper chelating activity in both acetone and methanol extracts (EC₅₀ values of 6.31 and 6.41 mg mL^-1). Relevant inhibition towards α-amylase (IC₅₀ values of 3.34 and 4.53 mg mL^-1) and tyrosinase (with IC₅₀ ranging from 3.82 to 5.47 mg mL^-1) was reported for acetone and methanol extracts, respectively. UHPLC-HRMS-based profiling revealed the presence of lipidic molecules, such as glycolipids, phospholipids, and betaine lipids with polyunsaturated carbon chains, together with carotenoids, including canthaxanthin and adonixanthin, which are likely responsible for the observed bioactivities.