Tricaprylin, also known as glyceryl tricaprylate or trioctanoin, is a medium-chain triacylglycerol (TAG) formed by esterification of glycerol with three caprylic acid (octanoic acid, C8:0) chains. This neutral lipid extends the short- to medium-chain TAG series, alongside compounds such as tributyrin and tricaproin, which are valued for their rapid energy availability and formulation stability.
Chemical Structure
Tricaprylin has the molecular formula C27H50O6 and a molecular weight of 470.7 g/mol. Its structure consists of a symmetric glycerol backbone esterified at the sn-1, sn-2, and sn-3 positions with straight-chain octanoyl groups. This configuration confers high lipophilicity (LogP 8.36–8.9) and makes the molecule readily susceptible to lipase-mediated hydrolysis, releasing caprylic acid for rapid metabolic utilization.
Physical Properties
Tricaprylin is a clear, colorless to pale yellow oily liquid with a density of 0.95–0.96 g/cm³ at 20 °C. It has a melting point of approximately 9–10 °C, a boiling point of around 230 °C at 1 mmHg, and a flash point near 210 °C. Insoluble in water (<1 mg/mL), it is fully miscible with ethanol, chloroform, and lipid solvents. Its low volatility and resistance to oxidation contribute to excellent stability, even under elevated temperature conditions.
Biological Functions
Following ingestion, tricaprylin is rapidly hydrolyzed by pancreatic lipases in the small intestine. The released medium-chain fatty acids are transported directly via the portal vein to the liver, where they undergo β-oxidation and ketogenesis. This metabolic pathway bypasses adipose tissue storage and minimizes insulin response, supporting sustained energy delivery. Additionally, caprylic acid derived from tricaprylin may exert modulatory effects on gut microbiota and display mild antimicrobial activity.
