作者: Friedrichs, Silvia ; Mulder, Monique T ; Gutbrod, Katharina ; Kerksiek, Anja ; Liu, Hong-Bing ; Zhan, Na ; Dubbeldam, Marco ; Lütjohann, Dieter ; Vanbrabant, Kenneth ; Vanmierlo, Tim ; Van Meel, David ; Schepers, Melissa ; Dörmann, Peter

Enhancing the cholesterol turnover in the brain via activation of liver x receptors can restore memory in a mouse model for Alzheimer's disease. The edible Asian brown alga Sargassum fusiforme (Hijiki) contains high amounts of oxysterols such as (3β, 24ξ)-stigmasta-5, 28-dien-3, 24-diol (24[R, S]-saringosterol) that are a potent liver x receptor agonists. We aimed to find native European seaweed species with contents of 24(R, S)-saringosterol that are comparable to those found in Sargassum fusiforme. Additionally, we hypothesize that seasonal variations modify the amount of 24(R, S)-saringosterol in seaweeds. Sterols and oxysterols were extracted with chloroform/methanol from various seaweed species harvested in the Eastern Scheldt in different seasons between October 2016 and September 2017. Identification and quantification of the lipids was performed by gas chromatography- mass spectrometry and gas chromatography- flame ionization detection. We confirmed that brown algae Undaria pinnatifida harvested in February and Sargassum muticum harvested in October contained the highest amounts of 24(R, S)-saringosterol (32.4 ± 15.25 μg/g, mean ± S.D. and 32.95 ± 2.91 μg/g, respectively) and its precursor fucosterol (1.48 ± 0.11 mg/g), higher than Sargassum fusiforme (20.94 ± 3.00 μg/g, mean ± S.D.), while Ascophyllum nodosum and Fucus vesiculosus and Fucus serratus contained amounts of 24(R, S)-saringosterol (22.09 ± 3.45 μg/g, 18.04 ± 0.52 μg/g and 19.47 ± 9.01 μg/g, mean ± S.D., respectively) comparable to Sargassum fusiforme. In other algae only minor amounts of these sterols were observed. The green algae Ulva lactuca contained only 0.29 mg/g fucosterol and 10.3 μg/g 24 (R, S)-saringosterol, while all investigated red algae did not contain any 24(R, S)-saringosterol or fucosterol. In the Eastern Scheldt algae harvested in September/October delivered the highest yield for 24(R, S)-saringosterol, with the exception of Undaria pinnatifida that showed the highest levels in February. We showed that exposure of lipid extracts of Ulva lactuca to sunlight at room temperature or in the presence of oxygen to UV-C light lead to the quantitative conversion of fucosterol into 24(R, S)-saringosterol. Exposing pure fucosterol to UV-light did not convert any fucosterol into 24(R, S)-saringosterol underscoring the requirement of seaweed constituents in the conversion of fucosterol into 24(R, S)-saringosterol. In conclusion, we showed that brown seaweeds harvested from the Eastern Scheldt contain amounts of 24(R, S)-saringosterol comparable to Sargassum fusiforme, varying per season and showing the highest amounts in spring. In accordance with these observations the amount of 24(R, S)-saringosterol in the brown seaweeds can be modulated by light.

2021-04-01·Analytical and Bioanalytical Chemistry

Molecular insights into symbiosis—mapping sterols in a marine flatworm-algae-system using high spatial resolution MALDI-2-MS imaging with ion mobility separation

Article

作者: Dreisewerd, Klaus ; Soltwisch, Jens ; Hambleton, Elizabeth A ; Bien, Tanja

AbstractWaminoa sp. acoel flatworms hosting Symbiodiniaceae and the related Amphidinium dinoflagellate algae are an interesting model system for symbiosis in marine environments. While the host provides a microhabitat and safety, the algae power the system by photosynthesis and supply the worm with nutrients. Among these nutrients are sterols, including cholesterol and numerous phytosterols. While it is widely accepted that these compounds are produced by the symbiotic dinoflagellates, their transfer to and fate within the sterol-auxotrophic Waminoa worm host as well as their role in its metabolism are unknown. Here we used matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging combined with laser-induced post-ionization and trapped ion mobility spectrometry (MALDI-2-TIMS-MSI) to map the spatial distribution of over 30 different sterol species in sections of the symbiotic system. The use of laser post-ionization crucially increased ion yields and allowed the recording of images with a pixel size of 5 μm. Trapped ion mobility spectrometry (TIMS) helped with the tentative assignment of over 30 sterol species. Correlation with anatomical features of the worm, revealed by host-derived phospholipid signals, and the location of the dinoflagellates, revealed by chlorophyll a signal, disclosed peculiar differences in the distribution of different sterol species (e.g. of cholesterol versus stigmasterol) within the receiving host. These findings point to sterol species-specific roles in the metabolism of Waminoa beyond a mere source of energy. They also underline the value of the MALDI-2-TIMS-MSI method to future research in the spatially resolved analysis of sterols.

2020-05-01·Chemistry of Natural Compounds

Steroids from the Brown Alga Sargassum naozhouense

作者: Yonghong Liu ; Riming Huang ; Yan Peng

Our previous investigation of the chem. constituents of this species resulted in the isolation of some secondary metabolites, i.e., norisoprenoids.In this present investigation, 10 known steroids were isolated and identified as fucosterol (1), saringosterol (2), 24-ketocholesterol (3), 24-hydroperoxy-24-vinylcholesterol (4) , cholesterol (5), 3β,28ξ-dihydroxy24-ethylcholesta-5,23Z-diene (6), 3β-hydroxystigmasta-5,24E(28)-diene-29-aldehyde (7), 3β-hydroxystigmasta5,24Z(28)-diene-29-aldehyde (8), 24R,28R- and 24S,28S-epoxy-24-ethylcholesterol (9), and cholest-5(6)-en-3β-sodium sulfate (10).All compounds were isolated for the first time from S. naozhouense collected off the coast of Leizhou Peninsula. Furthermore, compounds 7 and 8 were isolated from marine algae for the first time.The dried seaweed S. naozhouense (10 kg) was extracted with 90% EtOH.The extract was concentrated under reduced pressure and partitioned successively with petroleum ether (PE), CHCl3, EtOAc, and BuOH.The PE fraction was chromatographed on silica gel and eluted with a gradient of PE-EtOAc (100:0, 50:1, 10:1, 5:1, 2:1, 0:1) to yield 10 fractions.Fraction 1 was separated by silica gel column chromatog. and HPLC to give compounds 1 (3.4 mg), 2 (4.5 mg), 3 (3.3 mg), and 4 (3.5 mg).Fraction 2 was separated by silica gel column chromatog., Sephadex LH-20, and HPLC to afford 5 (3.2 mg) and 6 (4.3 mg).Fraction 8 was separated by silica gel column chromatog., Sephadex LH-20, and HPLC to yield 7 (3.1 mg), 8 (3.0 mg), and 9 (4.5 mg).The n-BuOH fraction was chromatographed over Sephadex LH-20, eluting with CHCl3-MeOH (1:1), and then repeatedly subjected to column chromatog. on silica, eluting with CHCl3-MeOH (from 9:1 to 8:2) to yield 10 (2.5 mg).

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适应症	最高研发状态	国家/地区	公司	日期
心血管疾病	临床前	中国	中国海洋大学	2023-01-09
心血管疾病	临床前	荷兰	Erasmus MC	2023-01-09
神经退行性疾病	临床前	中国	中国海洋大学	2023-01-09
神经退行性疾病	临床前	荷兰	Erasmus MC	2023-01-09