Acetyl- and butyrylcholinesterase inhibitory activities of sterols and phlorotannins from Ecklonia stolonifera

Abstract

As part of this study on the isolation of cholinesterase inhibitors from natural marine products, the bioactivity of the ethanolic extracts from 27 Korean seaweeds were screened using acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory assays. Ecklonia stolonifera exhibited promising inhibitory properties against both AChE and BChE. Bioassay-guided fractionation of the active n-hexane and ethyl acetate (EtOAc) soluble fractions, obtained from the ethanolic extract of E. stolonifera, resulted in the isolation of the sterols; fucosterol (1) and 24-hydroperoxy 24-vinylcholesterol (2), from the n-hexane fraction and the phlorotannins; phloroglucinol (3), eckstolonol (4), eckol (5), phlorofucofuroeckol-A (6), dieckol (7), triphlorethol-A (8), 2-phloroeckol (9) and 7-phloroeckol (10), from the EtOAc fraction. Of these, compounds 2, 9 and 10 were isolated from E. stolonifera for the first time. Compounds 4-7, 9 and 10 exhibited inhibitory potential against AChE, with 50% inhibition concentration (IC50) values of 42.66 Ϯ 8.48, 20.56 Ϯ 5.61, 4.89 Ϯ 2.28, 17.11 Ϯ 3.24, 38.13 Ϯ 4.95 and 21.11 Ϯ 4.16 mM, respectively; whereas, compounds 1, 2, 4 and 6 were found to be active against BChE, with IC50 values of 421.72 Ϯ 1.43, 176.46 Ϯ 2.51, 230.27 Ϯ 3.52 and 136.71 Ϯ 3.33 mM, respectively. It has been suggested that the inhibition of these enzymes by the sterols and phlorotannins derived from marine brown algae could be a useful approach for the treatment of Alzheimer's disease.

Neuroprotective effect of the marine macroalgaGelidiella acerosa: identification of active compounds through bioactivity-guided fractionation

“…Apart from antioxidant activity, the benzene:ethyl acetate fractions (F9-F13) also showed inhibitory activity against both AChE and BuChE. Yoon et al (2008) demonstrated that the hexane:ethyl acetate fractions obtained from an ethanolic extract of the marine brown alga, Ecklonia stolonifera Okamura (Lessoniaceae) was found to exhibit inhibitory potential against AChE and BuChE. Since the benzene:ethyl acetate fractions (F9-F14) were found to possess both antioxidant and antiChE activities, these fractions were pooled together and again verified for the activities.…”

Nostotrebin 6, a bis(cyclopentenedione) with cholinesterase inhibitory activity isolated from Nostoc sp. str. Lukešová 27/97

“…Nostocarboline, a quaternary -carboline alkaloid produced by the cyanobacterium Nostoc 78-12A, inhibits both AChE (IC 50 = 5.3 M) and BChE (IC 50 = 13.2 M) 7,8 . Ecklonia stolonifera Okamura is a producer of several ChE inhibitors, belonging to the sterol and phlorotannin groups 9 . The most active is the phlorotannin (named phlorofucofuroeckol-A), a reversible inhibitor of both AChE (IC 50 = 4.98 M) and BChE (IC 50 = 136.71 M).…”

“…Algae and cyanobacteria are also a promising source for structurally new types of secondary metabolites, as well as unique biological activities; this is due to their differences in metabolism, compared to higher plants 3 . However, to date only a few algal and cyanobacterial strains have been studied for ChE inhibitors despite the increasing interest in the secondary metabolites of these microorganisms [4][5][6][7][8][9] . Based on our screening for AChE inhibitory activity in cyanobacteria and algae originating from different types of habitat and geographical areas, we have selected one of the most active cyanobacterial strains (Nostoc sp.…”

Characterization of Black Ginseng Extract with Acetyl- and Butyrylcholinesterase Inhibitory and Antioxidant Activities

“…3). The rate of the AChE-mediated hydrolysis of acetylthiocholine was determined by measuring the rate of production of free sulfur groups produced as acetylthiocholine was hydrolyzed to thiocholine [19]. On learning and memory deficits associated with SCOP treatment model, the increased AChE activity produced by SCOP was significantly inhibited by WGE and BGE (p<0.001) [17].…”