Oleate hydroxylase involved in the biosynthesis of ricinoleate (PubMed:27830762, PubMed:22370951). Exhibits delta(12) hydroxylase activity on 16C and 18C monounsaturated fatty acids (e.g. oleic and palmitoleic acids), and, to a lower extent, gamma(3) hydroxylase activity on ricinoleic acid (PubMed:18467452, PubMed:27830762). It uses cytochrome b5 as an electron donor. May act on both oleic acid (18:1(9cis)) and eicosenoic acid (20:1(11cis)) (By similarity). (9Z)-octadecenoate + AH2 + O2 = (12R)-hydroxy-(9Z)-octadecenoate + A + H2O Lipid metabolism; monounsaturated fatty acid biosynthesis. The histidine box domains may contain the active site and/or be involved in metal ion binding. Mediates gamma(3) desaturated fatty acids (e.g. densipolic acid) and ricinoleic acid accumulation when expressed in S.pombe with a temperature-dependent toxicity, at 30 degrees Celsius but not at 37 degrees Celsius. Triggers hydroxyl fatty acids accumulation in seeds when expressed in A.thaliana under the guidance of a seed-specific promoter. Promotes ricinoleic acid biosynthesis when expressed in C.gracilis. Belongs to the fatty acid desaturase type 1 family.