Monoarachidin, also known as 1-monoarachidin or 1-arachidonoylglycerol, is a monoglyceride produced by the esterification of glycerol with arachidonic acid, an important polyunsaturated fatty acid involved in lipid signaling pathways.
Chemical Structure
Monoarachidin has the chemical formula C23H38O4 and a molecular weight of approximately 378.6 g/mol. Its structure consists of a glycerol backbone esterified at the sn-1 position with arachidonic acid (20:4 n-6), which contains four cis double bonds (at positions 5Z, 8Z, 11Z, and 14Z). This configuration contributes to its relatively high lipophilicity, with an estimated XLogP3 value in the range of 6–7, and a polar surface area of approximately 66.8 Ų.
Physical Properties
In its pure form, monoarachidin is typically observed as a clear, pale yellow oil or solid. Predicted physical properties include a density of approximately 0.992 g/cm³ and a boiling point near 509°C, with a pKa value of about 13.15. The compound displays limited solubility in common organic solvents such as chloroform and methanol, while exhibiting very low solubility in water (~0.0012 mg/L), consistent with the behavior of amphiphilic lipid molecules.
Biological Role
Monoarachidin is an isomer of 2-arachidonoylglycerol (2-AG), a well-characterized endocannabinoid. However, monoarachidin demonstrates weaker affinity and agonist activity at the cannabinoid CB1 receptor compared to 2-AG. It can be formed via isomerization of 2-AG and is relevant in studies of endocannabinoid signaling, lipid metabolism, and the synthesis of eicosanoid precursors. Through its relationship with arachidonic acid pathways, monoarachidin may contribute to anti-inflammatory effects and other lipid-mediated biological processes.
Synthesis and Sources
Monoarachidin can be synthesized either enzymatically or chemically from arachidonic acid and glycerol. In biological systems, it is found in trace amounts in tissues as a product of triglyceride lipase digestion. High-purity monoarachidin (>98%) is also commercially available for research applications in lipid biochemistry and related fields.