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Compositional guideline: Palmidrol

13 July 2021

Name of the ingredient

Palmidrol (AAN)

Definition of the ingredient

The substance is N-(2-Hydroxyethyl)hexadecanamide (N-palmitoylethanolamine, PEA).

Palmidrol is an endogenous fatty acid amine. Palmidrol synthesis is conducted by dehydration of the hot molten salt of ethanolamine palmitate, in solvent free condition and ethanolamine excess. The crude reaction product thus obtained is further purified by crystallization from alcohol.

Molecular formula: C18H37NO2

Structure: Structure of Palmidrol

CAS Number: 544-31-0

Table 1. Ingredient specific requirements
Test Method reference Acceptance criteria
Appearance Visual White crystalline powder

Ph. Eur 2.2.3
Potentiometric determination of pH

6.0-.5 ( water suspension at 100mg/mL)

Ph Eur 2.2.25
(Absorption spectrophotometry, ultraviolet and visible)

A 1%/1cm/300nm

1% solution in isopropyl alcohol heat up to solubilisation

<0.005 AU
Smell   Free of ammonia and amine
Solubility Product suspended in solvents listed.

Almost insoluble in water

≥5mg/ml in DMSO

≥10mg/ml in n-octanol

≥10mg/ml in warm ethanol

Loss on Drying USP <731> <0.5%
Particle Size Direct light scattering 10 - 100µm
TLC Ph Eur 2.2.27 (Thin-layer chromatography) The principal spot in the chromatogram obtained for the sample solution is in a similar position to the Palmidrol standard solution
Melting Point Ph Eur 2.2.15. (Melting point - open capillary method) 98-102°C
IR Spectrum Ph Eur (2.2.24 Absorption spectrophotometry infrared). IR absorption maxima correspond in position and relative intensity to those in the spectrum obtained with the palmidrol standard
Palmidrol HPLC Method 98-102% w/w
Table 2. Incidental constituents
Test Method reference Acceptance criteria
Residual solvents
Isopropanol Ph Eur 2.4.24 < 1000 ppm (Isopropanol)
Incidental metals and non-metals
Total Heavy Metals Ph Eur 2.4.8 Total Heavy Metals <10ppm
Aluminium ICP-OES Not more than 100 ppm
Nickel ICP-OES Not more than 30 ppm
Other organic or inorganic impurities or toxins
Free Palmitic acid (PA) HPLC ≤0.50% w/w
Myristoylethanolamide (MEA) HPLC Myristoylethanolamide (MEA) ≤0.20% w/w
Stearoylethanolamide (SEA) HPLC Stearoylethanolamide (SEA) ≤0.20%
Each other unknown impurity HPLC ≤0.10% w/w for each unknown
Total impurities HPLC ≤2.00% w/w
Free ethanolamine HPLC <0.3% (Spectrophotometric, OPA- derivative) <1.0% w/w
Ash (sulfuric) Ph Eur 2.4.14 <0.1% w/w

Key to abbreviations

BP = British Pharmacopoeia

HPLC = High-pressure liquid chromatography

IR = Infrared spectrophotometry

PCBs = Polychlorinated biphenyls

Ph Eur = European Pharmacopoeia

TLC = Thin layer chromatography

USP = United States Pharmacopoeia