Converts loganin into secologanin. loganin + O2 + reduced [NADPH--hemoprotein reductase] = H(+) + 2 H2O + oxidized [NADPH--hemoprotein reductase] + secologanin Alkaloid biosynthesis; secologanin biosynthesis. Tonoplast. Upper and lower leaf epidermis. Belongs to the cytochrome P450 family.