Trimyristin, also known as glyceryl trimyristate, is a saturated triacylglycerol (TAG) composed of three myristic acid (tetradecanoic acid, C14:0) chains esterified to a glycerol backbone. This waxy solid is naturally abundant in nutmeg, palm kernel, and coconut oils, representing approximately 8–19% of nutmeg butter. It extends the medium-chain TAG series following trilaurin and is widely used in lipid chemistry research and teaching laboratories, particularly for extraction and purification demonstrations.

Chemical Structure

Trimyristin has the molecular formula C₄₅H₈₆O₆ and a molecular weight of 723.16 g/mol. Its symmetric sn-glycerol backbone esterified at the sn-1, sn-2, and sn-3 positions with straight-chain myristoyl groups confers pronounced hydrophobicity (logP ≈ 14.09; log₁₀ water solubility ≈ −15.36). This structure facilitates enzymatic hydrolysis by lipases, yielding free myristic acid.

Physical Properties

Trimyristin appears as a white to yellowish-gray crystalline powder with a melting point of 56–57 °C and a density ranging from 0.862 to 0.885 g/cm³ at 40–60 °C. Its calculated boiling point is approximately 1457 K. The compound is odorless, insoluble in water, but readily soluble in hot ethanol, chloroform, ether, and dichloromethane. It exhibits polymorphism, with an enthalpy of fusion (ΔH_fus) between 117 and 152 kJ/mol, forming stable β-crystalline structures that make it particularly suitable for recrystallization-based extraction protocols.

Biological Functions

Upon digestion, trimyristin is hydrolyzed by pancreatic lipases to release myristic acid. This fatty acid integrates into cellular membranes, accounting for approximately 5% of phospholipid fatty acid content, and can activate immune-related signaling pathways such as TLR4/NF-κB. Metabolically, trimyristin serves as a sustained energy source via β-oxidation, although its oxidation rate is slower than that of medium-chain triglycerides (MCTs). At excessive dietary levels, it has been associated with increased plasma cholesterol concentrations.