Monocaprin, also known as 1-monodecanoyl-rac-glycerol or glycerol monodecanoate (C₁₃H₂₆O₄, molecular weight 246.34 g/mol), is a medium-chain monoacylglycerol (MAG) formed by esterification of decanoic acid (capric acid, C10:0) at the sn-1 position of glycerol. This compound is part of the monoacylglycerol family, alongside monocaprylin and monobutyrin, and is widely studied for its physicochemical characteristics and biological functionality in lipid research and applied biochemistry.
Chemical Structure
Monocaprin consists of a glycerol backbone esterified with a single decanoyl chain (-CO(CH₂)₈CH₃) at the primary sn-1 hydroxyl group, leaving two free hydroxyl groups at the sn-2 and sn-3 positions. Its systematic IUPAC name is 2,3-dihydroxypropyl decanoate, with the molecular formula CH₂(OCOC₉H₁₉)-CH(OH)-CH₂OH. The compound appears as a white to off-white solid with a melting point of 51–53 °C and exhibits solubility in organic solvents such as chloroform and dimethyl sulfoxide (DMSO), while being only sparingly soluble in water (~600 mg/L at 33 °C). Its structure is further confirmed by the InChI descriptor: InChI=1S/C13H26O4/c1-2-3-4-5-6-7-8-9-13(16)17-11-12(15)10-14/h12,14-15H,2-11H2,1H3.
Physicochemical Properties
Monocaprin has an estimated boiling point of approximately 309 °C, a density of about 0.97 g/cm³, and a refractive index close to 1.428. The pKa is around 13.2, reflecting the weak acidity of its alcoholic hydroxyl groups. Due to its amphiphilic character (hydrophilic–lipophilic balance, HLB ≈ 4–6), monocaprin is capable of forming organized supramolecular assemblies such as micelles, lamellar phases, and cubic liquid-crystalline structures. It demonstrates high thermal stability and resistance to mild hydrolytic conditions. The presence of the C10 fatty acyl chain provides an optimal balance between lipophilicity and membrane affinity, enabling effective interactions with lipid bilayers without excessive membrane disruption.
Synthesis and Stability
Monocaprin is commonly synthesized by enzymatic glycerolysis of tricaprin or by lipase-catalyzed transesterification of ethyl decanoate with glycerol, using microbial enzymes such as those derived from Candida species. These processes typically yield product purities exceeding 90% following purification steps such as molecular distillation or controlled crystallization. The ester bond in monocaprin undergoes slow hydrolysis in the presence of lipases, resulting in the gradual release of free capric acid. This controlled degradation contributes to its sustained biological activity, particularly in antimicrobial and formulation-related applications.
