Tricaproin, also known as glyceryl trihexanoate or trihexanoin, is a medium-chain triacylglycerol (TAG) composed of three hexanoic acid (caproic acid, C6:0) chains esterified to a glycerol backbone. This neutral lipid functions as an efficient energy substrate, emulsifying agent, and drug carrier, extending the short-chain TAG series from tributyrin with improved physicochemical stability and solubility.
Chemical Structure
Tricaproin has the molecular formula C21H38O6 and a molecular weight of 386.5 g/mol. Its symmetric structure consists of a glycerol core esterified at the sn-1, sn-2, and sn-3 positions with straight-chain hexanoyl groups. This configuration confers high susceptibility to lipase-mediated hydrolysis and a logP value of approximately 6.3, reflecting a balanced lipophilicity suitable for biological and pharmaceutical applications.
Physical Properties
Tricaproin appears as a colorless to light yellow oily liquid, with a density of approximately 0.98 g/cm³ at 20 °C and a refractive index around 1.44. It exhibits a low melting point (−60 °C) and a boiling point of 244 °C at 28 mmHg. Insoluble in water, it is readily soluble in ethanol, ether, DMF, and DMSO (≥30 mg/mL). The compound remains stable at −20 °C and displays low viscosity, making it well suited for formulation purposes.
Biological Functions
Following ingestion, tricaproin is rapidly hydrolyzed by pancreatic lipases in the intestine, releasing caproic acid, a medium-chain fatty acid that readily enters mitochondrial β-oxidation without reliance on carnitine transport. This metabolic pathway supports rapid energy production and ketogenesis without significant triacylglycerol storage. In addition, tricaproin has been reported to influence gut microbiota composition and exhibits insect-repellent activity, likely related to the volatility of caproic acid derivatives.
