Tripalmitin, also known as glyceryl tripalmitate, is a saturated long-chain triacylglycerol (TAG) composed of three palmitic acid (hexadecanoic acid, C16:0) moieties esterified to a glycerol backbone. Naturally abundant in palm oil and animal fats, this lipid represents a higher homolog in the TAG series following trimyristin and is valued for its high melting point, structural stability, and relevance in food science and lipid research.
Chemical Structure
Tripalmitin has the molecular formula C51H98O6 and a molecular weight of 807.3 g/mol. Its symmetric sn-glycerol core is esterified at the sn-1, sn-2, and sn-3 positions with straight-chain palmitoyl groups. This structural symmetry confers pronounced hydrophobicity (logP ≈ 16.4; log10WS ≈ −17.9), promotes formation of stable β-crystalline polymorphs, and enables enzymatic hydrolysis by lipases to release free palmitic acid.
Physical Properties
Tripalmitin is a white crystalline solid with a melting point of approximately 65–67 °C, a density of 0.875 g/cm³ at 70 °C, and a boiling point around 315 °C at atmospheric pressure. It is insoluble in water but readily soluble in nonpolar organic solvents such as ether and chloroform, and in hot ethanol. The compound exhibits characteristic lipid polymorphism (α → β′ → β transitions), with a fusion enthalpy ranging from 121 to 179 kJ/mol, making it suitable for studies of controlled crystallization and lipid phase behavior.
Biological Functions
In biological systems, tripalmitin is hydrolyzed by pancreatic lipases into glycerol and palmitic acid. Palmitic acid contributes to membrane rigidity, accounting for approximately 20–30% of fatty acids in phospholipids, and serves as a dense energy reserve in adipose tissue. However, excessive dietary intake of saturated TAGs such as tripalmitin has been associated with elevated LDL cholesterol levels and an increased risk of hyperlipidemia and cardiovascular disease.
