Microalgae as a new source of neuroprotective compounds

Uota, Sisay Tesema

http://hdl.handle.net/10400.1/15357

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Authors

Uota, Sisay Tesema

Advisor(s)

Barreira, Luísa

Katkam, Gangadhar N.

Abstract(s)

Although neurodegenerative diseases (NDD) mostly occur in aged people, its onset can also be triggered by excessive accumulation of metal ions, particularly copper, iron and calcium in the brain which leads to the development of Alzheimer‟s disease (AD). AD affects cognitive function in the elderly people. Therefore, there is an urgent need to search and identify new sources of anti-AD drugs from natural sources, because available drugs are aggressive and have side-effects. According to a neurotoxicology study, chelating or capturing those metals is a therapeutic solution. Interestingly, marine microalgae (MMA) are rich in several bioactive compounds with neuroprotective, anti-inflammatory and others. Recently, MMA have been featured in neuronal-related diseases. This research shows bioactive compounds produced by different microalgae as a source of neuroprotective agents, in terms of copper (Cu2+CA), iron (Fe2+CA) and calcium chelating activities (Ca2+CA). Hence, nine different microalgae were procured from Necton S.A, Portugal. Three different food graded solvents namely ethyl acetate, ethanol and water were used for extraction. The ethanolic extract of Porphyridium sp. and Skeletonema costatum were the most significantly bioactive with an IC50 of 1.44 mg/mL and 1.95 mg/mL for Cu2+CA, 0.942 mg/mL and 0.883 mg/mL for Fe2+CA and 0.832 mg/mL and 1.02 mg/mL for Ca2+CA respectively. The active crude extracts were further partitioned into hexane, dichloromethane, ethyl acetate and an aqueous alcoholic by liquid-liquid extraction (LLE). Hexane fractions of Porphyridium sp. and S. costatum presented high metal chelating activity with an IC50 of 0.461 mg/mL and 0.361 mg/mL for Cu2+CA, 0.292 mg/mL and 0.263 mg/mL for Fe2+CA and 0.451 mg/mL and 0.181 mg/mL for Ca2+CA respectively. In order to identify the compounds possibly responsible for the activity, the hexane fractions were analyzed by GC-MS. About 19 and 22 of compounds were in Porphyridium sp. and S. costatum identified, respectively, belonging to 4 classes of metabolites: fatty acids, sterols, alcohols and ethers. The most abundant compounds detected were long chain fatty acids and alcohols including t etrahydropyranyl ether of citronellol and 3,7,11,15-tetramethyl-2-hexadecen-1-ol. The analyzed species exhibited neuroprotective activities in a concentration dependent. Their metal chelating activities proves their potential for future application as natural remedies for Alzheimer‟s disease.