Abstract
When unsaponifiable mixture of the liver lipid of firefly squid Watasenia scintillans was analyzed by high performance liquid chromatography (HPLC), a large quantity of retinol (A-OH), presumed to be 11-cis A-OH, was detected. Several methods of isolation and purification were studied to identify the isomeric form. As the first step, a cholesterol was removed from a n-hexane solution of the mixture by keeping it at -20℃. The solution was fractionated by gel permeation chromatography on a column of Bio-Beads S-X3 with a mixed solvent of cyclohexane/dichloromethane (1:1). The object was isolated from the A-OH fraction by preparative HPLC on a silica gel column, using a mobile phase of n-hexane/1-octanol/2-propanol (98. 74 : 1.2 : 0.06) and purified on a reversed phase mini-column with 70% methanol in water, finally eluted from it with methanol. At these processes it should be noted that the oxidation from A-OH to retinal (A-CHO) occurs more easily than its cis-trans isomerization. The purified matter was identified as 11-cis A-OH by comparison of its UV, fluorescence and ^1H-NMR spectra with those of an authentic sample which was given from a photo-isomerization mixture of A-CHO. A-OH existed almost (in a 93% content of the total amount of A-OH) as the 11-cis form in the liver of firefly squid, and the presence was common between Decapoda and Octopoda.
