Brassicasterol 2966157 224042293 2008-07-07T01:38:42Z Kingdon 668610 /* Algal Sources */ link to taxa for which we have articles; italicize genus/species names {{Chembox new | Name = Brassicasterol | ImageFile = brassicasterol.svg <!-- | ImageSize = 260px --> | ImageName = Brassicasterol | IUPACName = 24-methyl cholest-5,22-dien-3β-ol | OtherNames = brassicasterol<br />(3β,22E)-ergosta-5,22-dien-3-ol<br />24β-methylcholesta-5,22-dien-3 beta-ol<br />ergosta-5,22-dien-3β-ol | Section1 = {{Chembox Identifiers | SMILES = CC(C)C(C)C=CC(C)C1(C2(C)(C(CC1)<br />C3(C(CC2)C4(C(=CC3)CC(O)CC4)(C)))) | CASNo = 474-67-9 }} | Section2 = {{Chembox Properties | Formula = {{carbon}}<sub>28</sub>{{hydrogen}}<sub>46</sub>{{oxygen}} | MolarMass = 398.67 g/mol | Appearance = white solid | Density = ? g/ml, solid at room temperature | Solubility = ? mg/l | MeltingPt = 150-151°C | BoilingPt = }} | Section7 = {{Chembox Hazards | ExternalMSDS = | MainHazards = | FlashPt = non-flammable | RPhrases = | SPhrases = }} | Section8 = {{Chembox Related | Function = Sterols | OtherFunctn = [[cholesterol]]<br />[[β-sitosterol]]<br />[[campesterol]]<br />[[stigmasterol]] }} }} '''Brassicasterol''' (24-methyl cholest-5,22-dien-3β-ol) is a 28 [[carbon]] [[sterol]] synthesised by several [[unicellular]] [[algae]] ([[phytoplankton]]) and some terrestrial plants ''e.g.'' [[oilseed rape]]. This compound has frequently been used as a [[biomarker]] for the presence of (marine) algal matter in the [[ecosystem|environment]]. ==Chemical Properties== ===Solubility === Brassicasterol has a low water [[solubility]] and consequently a high [[Partition coefficient|octanol – water partition coefficient]] (Kow = ??). This means that in most environmental systems, brassicasterol will be associated with the solid phase. ===Degradation=== In [[Hypoxia (environmental)|anaerobic]] sediments and soils, brassicasterol is stable for many hundreds of years enabling it to be used as an indicator of past algal production (see below). ===Chemical Analysis=== Since the [[molecule]] has a [[hydroxyl]] (-OH) group, it is frequently bound to other [[lipids]] including [[glycerol]]s; most analytical methods, therefore, utilise a strong [[alkali]] (KOH or NaOH) to [[saponify]] the [[ester]] linkages. Typical extraction [[solvents]] include 6% KOH in [[methanol]]. The free [[sterols]] are then separated from the [[polar lipids]] by partitioning into a less polar solvent (''e.g''. [[hexane]]). Prior to analysis, the hydroxyl group is frequently derivatised with [[BSTFA]] (bis-trimethyl silyl trifluoroacetamide) to replace the hydrogen with the less exchangeable trimethylsilyl (TMS) group. Instrumental analysis is frequently conducted on [[Gas Chromatograph]] (GC) with either a [[Flame Ionisation Detector]] (FID) or [[Mass Spectrometer]] (MS). The [[mass spectrum]] for the TMS ether of brassicasterol can be seen in the Figure.<br /> [[Image:mass spectrum brassicasterol.png|Mass fragmentation pattern for brassicasterol at 70eV on a Fisons MD800 mass spectrometer]] ==Formation and Occurrence== ===Algal Sources=== Brassicasterol is formed in plants from the [[isoprenoid]] [[squalene]] through [[campesterol]] as an intermediate. A list of the algae in which brassicasterol has been identified is shown below together with approximate composition (Data from an excellent review by Volkman, 1986). {| class="wikitable" |+ Sterol content of selected [[dinoflagellates]] (as percentage). Data from Volkman, 1986 |- !Species !A !B !C !D !E !F !G !H !others |- |''Gonyaulax'' spp||100||0||0||0||0||0||0||0||0 |- |''Peridinium foliaceum''||100||0||0||0||0||0||0||0||0 |- | ''Peridinium foliaceum'' ||80||20||0||0||0||0||0||0||0 |- |''Gonyaulax diegensis''||39||0||0||0||0||0||0||29||32 |- |''Pyrocystis lunula''||76||6||0||2||1||0||0||0||15 |- |''Gonyaulax polygramma''||36||1||0||9||7||0||0||0||47 |- |''[[Gymnodinium]] wilczeki''||26||39||0||35||1||0||0||0||0 |- |''Glenodinium hallii''||8||50||0||0||0||42||0||0||0 |- |''[[Noctiluca milaris]]''||0||1||1||5||73||0||6||0||14 |- |''Gymnodinium simplex''||0||0||0||0||53||0||0||0||47 |- |''Prorocentrum cordatum''||7||0||0||0||5||0||63||0||25 |} :A = [[cholesterol]] :B = [[campesterol]] :C = [[sitosterol]] :D = 22-dehydrocholesterol ((22''E'')-cholesta-5,22-dien-3β-ol) :E = BRASSICASTEROL :F = [[stigmasterol]] :G = 24-methylene cholesterol :H = [[fucosterol]] ===Other Sources=== ? ==Use as a Tracer for Marine Algae== The principal source of brassicasterol in the environment is from marine algae. Its relatively high concentration and stability allows it to be used in the assessment of the origin of organic matter in samples, especially sediments. ===Brassicasterol / Cholesterol Ratio=== [[Image:brassicasterol cholesterol ratio.png|The concentration of brassicasterol down a sediment core from Loch Striven, Scotland together with it ratio to cholesterol]] The concentration of brassicasterol in a core sample from [[Loch Striven]], [[Scotland]]. Highest values may be seen in the top sections of the sediment which decrease with depth. However, the cholesterol behaves similarly and the ratio brassicasterol / cholesterol is fairly uniform at all depths indicating either a comparable degradation rate with no change in source or different degradation rates and a change in source. ===Multivariate Analysis=== [[Multivariate Statistical Analyses]] such as [[Principal Component Analysis]] of a range of [[lipid]] biomarkers (''e.g.'' other sterols, [[fatty acids]] and [[fatty alcohols]]) enable identification of compounds that have similar origins or behaviour. An example can be seen in the loadings plot for sediment samples from the [[Mawddach]] Estuary, [[Wales]]. [[Image:brassicasterol PCA.png|Principal Component Analysis of several lipid biomarkers from the Mawddach Esturay - brassicasterol is highlighted in red]]<br /> The location of brassicasterol in this figure (shown in red) indicates that the distribution of this compound is similar to that of the short chain fatty acids and alcohols which are known to be of marine origin. The terrestrially derived biomarkers such as β-sitosterol are on the opposite side of the figure and are mutually exclusive. ==References== {{Unreferenced|date =September 2007}} <references/> [[Category:Sterols]] [[nl:Brassicasterol]] [[ja:ブラシカステロール]]