Phospholipid studies of marine organisms: V(1) new α-methoxy acids fromHigginsia tethyoides

The phospholipids of the demospongeHigginsia tethyoides are shown to have at least 16 long-chain α-methoxy acids, which represent a new class of fatty acids. Among them are the saturated α-methoxy acids containing 19-24 carbon atoms. The monounsaturated compounds are 2-OMe-Δ(17)-24:1, 2-OMe-Δ(18)-25:1, 2-OMeΔ(19)-26:1 and 2-OMe-Δ(21)-28:1. The major diunsatured ones were shown to be 2-OMe-Δ(5, 19)-26:2 and 2-OMe-Δ(7, 21)-28:2. Small amounts of 2-OMe-23∶1, 2-OMe-26∶3; 2-OMe-27∶1 and 2-OMe-28∶3 were also encountered. Structures of the minor monounsaturated compounds were tentatively assigned as 2-methoxy-16-tricosenoic acid and 2-methoxy-20-heptacosenoic acids. The double bonds of the fatty acids show all-cis configuration. Circular dichroism measurements indicate an R-configuration for the α-methoxy acids. The major component of the total phospholipid acid mixture is 5,9,23-triacontatrienoic acid. Possible biosynthetic routes to these unusual phospholipid acids are discussed. The major phospholipids were phosphatidylethanolamine, phosphatidylglycerol and phosphatidylserine. The distribution of fatty acids among the phospholipids was also investigated.