(A) Membranes are enriched in 13-hydroxy-9,10-epoxy-octadecenoate and 13,9,10-trihydroxy-octadecenoate; (B) These compounds are released as free acids via lipasemediated hydrolysis; (C) 13-hydroxy-9,10-epoxy-octadecenoate is converted to 13,9,10-trihydroxy-octadecenoate in low pH environment or by epoxide hydrolase; (D) Free 13-hydroxy-9,10-epoxy-octadecenoate (D1) and 13,9,10-trihydroxy-octadecenoate (D2) are inactivated by re-esterification; (E) Free 13-hydroxy-9,10-epoxy-octadecenoate and 13,9,10-trihydroxy-octadecenoate are dehydrogenated to produce 13-keto-9,10-epoxy-octadecenoate (E1) and 13-keto-9,10-dihydroxy-octadecenoate (E2).