*6.5. Sphingolipids and Phospholipids*

Both components are polar lipids. Sphingolipids are complex lipids that are derived from sphingosine (unsaturated amino alcohol with 18 carbons), which is joined to a long-chain fatty acid by an amide bond forming the ceramide. Sphingolipids of plants are mainly cerebrosides (mono- and oligohexosilceramides) with a sugar molecule such as glucose, galactose, mannose and inositol. They are commonly found in cell walls, lipoproteins and other lipid-rich structures [99]. Phospholipids are a kind of lipid made up of a glycerol molecule, two fatty acids (1,2-diacylglycerol) and a phosphate group.

There are few studies about polar lipids in almond oil. Phospholipids and sphingolipids are the main classes of polar lipids with approximately 78% and 22%, respectively [100]. Between phospholipids, lecithin or phosphatidylcholine (45%), phosphatidylethanolamine or cephalin (45%), phosphatidylinositol (8%) and fosfatidiglycerol acid (2%) are the main compounds [101]. Fang [102] studied the sphingolipids content in almond kernels and found that the concentration of cerebroside (d18:2-C16:0h-glucose) was 0.068 mg/g of almond.

Compared with other nuts, almonds might not be the first choice for phospholipids, with relatively low compounds abundance and content [103]. Only 1.67% of the total fat is phospholipids, in comparison with 3.81% found in pistachios. The fatty acids of 16:0, 18:0, 18:1 and 18:2 are the most common structures of the fatty acyl moiety in almonds; phosphocholine, phosphoetanolamine and phosphoinositol are three major phospholipids species detected in almonds, representing 84% of total phospholipids.
