An improved method for the synthesis of 1-monoolein

• Pure monoolein can be obtained on a 200 mmol scale.
• Monoolein synthesis by enzymatic reaction is greener compared to chemical reaction.
• It is the first time to use crystallization to purify MAGs from cleavage product.
• Purification of impure oleic acid instead of buying pure oleic acid reduces costs.

Monoacylglycerols (MAGs) are precursors for the synthesis of many active lipids and an important amphiphilic emulsifiers which are widely used in food, pharmaceutical, and cosmetic industries. In this study, we reported an improved method for the synthesis of 1-monoolein using 1,2-acetonide glycerol as starting reactant. Firstly, commercial oleic acid was purified using our previous method and then 1,2-acetonide-3-oleoylglycerol was synthesized by the esterification of 1,2-acetonide glycerol with purified oleic acid using Novozym 435 lipase as catalyst. Finally, the cleavage of unpurified 1,2-acetonide-3-oleoylglycerol in methanol was conducted to obtain 1-monoolein. The effects of reaction system, addition amount of solvent, lipase load, reaction temperature and time on 1,2-acetonide-3-oleoylglycerol content in the crude reaction mixture were investigated. Under the optimal conditions, 94.6% 1,2-acetonide-3-oleoylglycerol in crude reaction mixture was obtained. 1-Monoolein was synthesized further by cleaving unpurified 1,2-acetonide-3-oleoylglycerol in methanol at room temperature with Amberlyst-15 resin as catalyst. The cleavage reaction resulted in the formation of 76.5% 1-monoolein and 96.2% 1-monoolein was obtained at 72.8% yield after repeated recrystallization in hexane to remove nonpolar impurities and water washing to remove glycerol. The main novelties for the synthesis of 1-monoolein are the use of Novozym 435 lipase instead of chemical catalysts used in previous studies to catalyze the esterification of 1,2-acetnode glycerol with free fatty acids and scalable crystallization method used instead of column chromatography to purify 1-monoolein.

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