Monolaurin, also known as glycerol monolaurate or 1-lauroylglycerol (C₁₅H₃₀O₄, MW 274.40 g/mol), is a monoacylglycerol formed by esterification of lauric acid (dodecanoic acid, C12:0) at the sn-1 position of glycerol and is widely recognized for its broad-spectrum antimicrobial activity.
Chemical Structure
Monolaurin features a glycerol backbone esterified with a 12-carbon saturated fatty acyl chain (-CO(CH₂)₁₀CH₃) at the primary sn-1 hydroxyl group, leaving two free hydroxyl groups. Its IUPAC name is 2,3-dihydroxypropyl dodecanoate (CH₂(OCOC₁₁H₂₃)-CH(OH)-CH₂OH). It typically appears as a white to off-white crystalline powder with a slightly waxy texture at room temperature. The molecular structure is confirmed by the InChI identifier: InChI=1S/C15H30O4/c1-2-3-4-5-6-7-8-9-10-11-15(18)19-13-14(17)12-16/h14,16-17H,2-13H2,1H3.
Physicochemical Properties
Monolaurin exhibits a melting point in the range of 60–66 °C (literature value ~63 °C) and a boiling point of approximately 186 °C at 1 mmHg. It has low solubility in water (~6 mg/L) but is readily soluble in organic solvents such as methanol and chloroform (up to ~50 mg/mL). The density is approximately 0.97 g/cm³, with a refractive index near 1.435. Its pKa is estimated at ~13.16, and a LogP value of ~4.03 reflects significant lipophilicity, supporting its affinity for lipid membranes. Monolaurin remains chemically stable across pH 3–9 and temperatures up to 150 °C, and behaves as an amphiphile capable of forming micellar or lamellar phases, with a hydrophilic–lipophilic balance (HLB) of approximately 4.
Synthesis and Stability
Industrial production of monolaurin is typically achieved through glycerolysis of trilaurin or via enzymatic transesterification of ethyl laurate with glycerol using lipases (commonly from Candida antarctica). These processes yield approximately 45–90% monolaurin, accompanied by di- and trilaurin by-products that are subsequently separated using molecular distillation techniques. The ester bond in monolaurin undergoes slow hydrolysis by microbial lipases, gradually releasing lauric acid and thereby providing sustained antimicrobial activity while avoiding the volatility and acidity associated with free fatty acids.
