Analysis of sphingolipids in potatoes ( Solanum tuberosum L.) and sweet potatoes ( Ipomoea batatas (L.) Lam.) by reversed phase high‐performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC‐ESI‐MS/MS)

Ceramides and glucocerebrosides of potatoes ( Solanum tuberosum L.) and sweet potatoes ( Ipomoea batatas (L.) Lam.) were analyzed using RP‐HPLC‐ESI‐MS/MS. Ceramides and glucocerebrosides containing the three different long‐chain bases 4,8‐sphingadienine (d18:2 Δ4,Δ8 ), 4‐hydroxy‐8‐sphingenine (t18:1 Δ8 ), and 8‐sphingenine (d18:1 Δ8 ) acylated to saturated and unsaturated hydroxy‐ and nonhydroxy fatty acids with 16–26 carbon atoms were detected. For ceramides and glucocerebrosides 4,8‐sphingadienine (d18:2 Δ4,Δ8 ) was found as the major long‐chain base, with lesser amounts of 4‐hydroxy‐8‐sphingenine (t18:1 Δ8 ) and 8‐sphingenine (d18:1 Δ8 ). 2‐(α‐)Hydroxypalmitic acid (C16:0h) was the major fatty acid, which was found to be acylated to the long‐chain bases. For quantification of these compounds, an RP‐HPLC‐ESI‐MS/MS method with an “echo‐peak”‐technique simulating internal standard injection was developed. The analyzed samples of potatoes and sweet potatoes showed amounts of ˜0.1–8 μg/kg single ceramides and amounts up to 500 μg/kg glucocerebrosides, with C16:0h‐glucosyl‐4,8‐sphingadienine as the major component.