Linolelaidic Acid: Properties, Handling & Research Use Guide

Linolelaidic acid is the principal trans isomer of linoleic acid (9E,12E-octadecadienoic acid), widely used in lipid biochemistry research as an analytical standard and as a tool compound for studying the biological effects of trans polyunsaturated fatty acids.

Chemical Name

(9E,12E)-Octadeca-9,12-dienoic acid

Isomer Class

Trans, trans di-unsaturated C18 fatty acid (trans isomer of linoleic acid)

Molecular Formula

C18H32O2

Molecular Weight

280.45 g/mol

CAS Number

506-21-8

Primary Research Use

Lipid metabolism studies, trans fatty acid biology, analytical reference standard

SKU

L1500788

Chemical Identity and Physical Properties

Linolelaidic acid (CAS 506-21-8) is an 18-carbon, doubly unsaturated fatty acid carrying two trans double bonds at positions Δ9 and Δ12, giving it the systematic name (9E,12E)-octadeca-9,12-dienoic acid. It is the geometric (trans,trans) isomer of linoleic acid, which bears the corresponding cis,cis configuration.

The all-trans double-bond geometry confers a more linear, extended hydrocarbon chain relative to its cis counterpart, resulting in a higher melting point than linoleic acid and altered membrane-packing behavior when incorporated into phospholipid bilayers. The compound appears as a white to off-white solid or waxy material at room temperature and is soluble in common organic solvents such as ethanol, chloroform, and DMSO, but is only sparingly soluble in water.

Key identifiers: Molecular formula C₁₈H₃₂O₂; MW 280.45 g/mol; CAS 506-21-8.

Storage, Handling, and Safety Guidelines

Storage: Store Linolelaidic acid under inert atmosphere (nitrogen or argon) at –20 °C, protected from light and moisture. Oxidative degradation of the bis-allylic positions can occur at ambient temperature; therefore, aliquoting stock solutions into single-use vials is strongly recommended to minimize freeze–thaw cycling and headspace oxygen exposure.

Solvent preparation: For biological assays, dissolve the compound in a minimal volume of ethanol or DMSO, then dilute into aqueous buffer. Ensure the final DMSO concentration does not exceed 0.1 % (v/v) in cell-based assays unless appropriate vehicle controls are included. Verify complete dissolution by visual inspection or UV absorbance before use.

Handling precautions: Use standard laboratory PPE (nitrile gloves, safety spectacles, lab coat). Avoid prolonged inhalation of dust or aerosols. As with most unsaturated fatty acids, the compound is not classified as acutely hazardous under GHS criteria, but specific SDS data should be consulted for the supplied lot. Dispose of waste in accordance with local regulations for organic chemical waste.

Stability monitoring: Assess solution freshness by GC or TLC before critical experiments. A shift in Rf value or emergence of additional GC peaks may indicate oxidation or isomerisation.

Research Applications

Analytical reference standard: Linolelaidic acid is used as a certified or research-grade standard for quantification of trans fatty acids in food, plasma, and tissue lipid extracts by GC-FID and GC-MS methods. Its well-defined double-bond geometry allows unambiguous chromatographic identification of the 9E,12E isomer.

Membrane biophysics: Incorporation studies use Linolelaidic acid to examine how trans polyunsaturated fatty acids alter membrane fluidity, lipid raft organisation, and phospholipid packing compared with their cis counterparts. Such experiments are relevant to understanding the impact of dietary trans fats on cell membrane function.

Cell biology and metabolism: Researchers supplement cell culture media with Linolelaidic acid to study its uptake, β-oxidation, and incorporation into glycerophospholipids and triglycerides. Comparative experiments with linoleic acid help elucidate structure–activity relationships of geometric isomers in lipid signalling pathways, including eicosanoid precursor competition and PPAR activation.

Nutrition and disease research: As a model trans fatty acid, Linolelaidic acid is used in mechanistic studies exploring associations between trans PUFA intake and outcomes such as inflammation, cardiovascular risk markers, and insulin signalling, complementing epidemiological observations with controlled in vitro evidence.

Quality Considerations and Experimental Best Practices

Purity verification: Confirm purity by GC (≥98 % recommended for mechanistic studies) and verify isomeric identity by NMR or GC-MS before initiating critical experiments. Trans-isomer contamination with residual cis-isomer (linoleic acid) can confound results, particularly in competitive assays.

Concentration accuracy: Weigh the compound on a calibrated analytical balance, accounting for moisture content if hygroscopic lots are used. For stock solutions, determine exact concentration by gravimetric calculation or UV/GC assay.

Vehicle and concentration controls: Always include a solvent-only control and, where feasible, a linoleic acid (cis,cis) comparator to isolate geometric-isomer-specific effects from general fatty acid effects.

Albumin complexation: For aqueous delivery to cells, consider complexing Linolelaidic acid with fatty-acid-free BSA at a defined molar ratio (commonly 2–6:1 fatty acid:BSA) to improve bioavailability and reduce cytotoxicity from micelle formation at higher concentrations.

Documentation: Record lot number, receipt date, storage conditions, and solution preparation details in the laboratory notebook to ensure reproducibility and traceability.

Frequently asked questions

What is the difference between Linolelaidic acid and Linoleic acid?

Both are C18:2 fatty acids with double bonds at positions 9 and 12, but Linoleic acid has a cis,cis (9Z,12Z) configuration while Linolelaidic acid has a trans,trans (9E,12E) configuration. This geometric difference produces a more extended molecular conformation, higher melting point, and distinct biological behavior, particularly in membrane incorporation and lipid metabolism pathways.

How should I prepare a working solution of Linolelaidic acid for cell culture experiments?

Dissolve Linolelaidic acid in a minimal volume of ethanol or DMSO to prepare a concentrated stock (typically 10–100 mM), then store aliquots under nitrogen at –20 °C. For cell treatment, dilute the stock into serum-free or fatty-acid-free BSA-supplemented medium at the desired working concentration, keeping final organic solvent below 0.1 % (v/v). BSA complexation (molar ratio ~4:1 fatty acid:BSA) is recommended to enhance aqueous solubility and controlled delivery.

Is Linolelaidic acid suitable for use as a GC reference standard for trans fatty acid analysis?

Yes. Linolelaidic acid is widely employed as a reference standard to identify and quantify the 9E,12E trans,trans isomer of linoleic acid in GC-FID and GC-MS lipid profiling. It is essential to verify lot purity (ideally ≥98 % by GC) and isomeric homogeneity before use as a quantitative standard, and the compound should be stored and handled under conditions that prevent oxidation and isomeric interconversion.

What concentration range is typically used for in vitro cell studies with Linolelaidic acid?

Reported in vitro concentrations vary widely depending on the cell type and experimental objective, but many mechanistic studies use concentrations in the range of 25–200 µM complexed with BSA. It is advisable to perform a preliminary dose-response and cell viability assessment for each specific cell model to determine the non-cytotoxic working range before proceeding with functional assays.

How can I confirm that my Linolelaidic acid stock has not degraded?

Assess stock integrity by GC analysis: a single sharp peak at the expected retention time for the 9E,12E isomer, with no significant additional peaks, indicates the material is intact. TLC can also be used as a rapid screen. Visible discoloration, an off-odor, or a shifted Rf value are practical indicators of degradation; in such cases, prepare a fresh stock from a newly opened aliquot stored under nitrogen.

References

1. Christie, W.W. (2022). Fatty Acids: Nomenclature, Structure and Function. AOCS Lipid Library. General textbook-level reference for fatty acid geometry and nomenclature.
2. Pariza, M.W. et al. Trans fatty acids and cardiovascular disease risk: a review. General reference — author names and journal details require verification.
3. Mensink, R.P. (2016). Effects of saturated fatty acids on serum lipids and lipoproteins: a systematic review and regression analysis. WHO Report. Referenced here for context on fatty acid classification.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.