Polarography of conjugated unsaturated lipids

Abstract

Conjugated fat-soluble vitamins, methylenic interrupted and conjugated fatty acids were polarographically investigated in both basic and neutral solvents. The half-wave potentials of all-trans-retinol, 13-cis-retinol, all-trans-retinyl acetate, all-trans-retinal, and Vitamin D(2) and D(3) were related to the number of double bonds in conjugation and their geometrical configuration. A minimum of three double bonds in conjugation and their geometrical configuration. A minimum of three double bonds in conjugation was required before reduction took place at the cathode, and as the number of conjugated bonds increased in the lipid compounds, the initial reduction wave took place at a lower half-wave potential.Investigation of conjugated double bonds in triglycerides and in alkali-isomerized linolenic and arachidonic acids gave reduction waves the half-wave potentials of which were related to the number of double bonds in conjugation. In both basic and neutral solvents there was a minimum of three double bonds in conjugation necessary to obtain a reduction wave at the dropping mercury electrode. Ultraviolet absorption curves of the prolonged reduction of polyunsaturated conjugated fatty acids indicate a step-wise reduction of each end of the polyunsaturated conjugated double bonds.In neutral solvent the log of the conjugated double bonds versus the half-wave potential (versus mercury pool anode) gave a linear equation, E(1)=2.98-1.6 log C. A proposed mechanism for the step-wise reduction of conjugated lipids is presented and discussed.

Contrasting Voltammetric Behavior of Different Forms of Vitamin A in Aprotic Organic Solvents

“…However, when conducting the reductive electrolysis at 253 K, it was possible to record up to the transfer of 4e – per molecule, which indicates that the temperature has an effect on the electrochemical reduction of 1 . , There has been some controversy as to how many electrons are involved in the reduction reaction of 1 . Earlier studies by Takahashi and Tachi , and Kuta and Ju , suggested a 4e – reduction process, while Mairanovsky et al, Valentin Pfund et al, and Park suggested a 1e – process.…”

“…33,37 There has been some controversy as to how many electrons are involved in the reduction reaction of 1. Earlier studies by Takahashi and Tachi 10,11 and Kuta and Ju 51,52 suggested a 4e − reduction process, while Mairanovsky et al, 23 Valentin Pfund et al, 24 and Park 14 suggested a 1e − process.…”

Organic polarography

“…Polarographic data were reported for conjugated unsaturated lipids in basic and neutral solvents (728), for vitamin D and related compounds (832); for retinal, retinol, and other Vitamin A derivatives in dimethylformamide and in presence of proton donors (833, 836); for 9 cyclic polyenes (160); for 9amino-10-phenylanthracene (202); for tetracene (507); for trans-and cisdinaphthylenecyclobutane and acenaphthylene (407); for acetylene and distyrybenzenes derivatives (409); and for vitamin A and related compounds in benzene-acetonitrile solution (1281). 2-carbethoxy derivatives in nonaqueous solvents and in the presence of phenol (1027); and (C6H5)2CH, (C6H5)3C+, (C6H5)2CCH3 in CH2C12 and 97% H2S04 (569) were studied by polarography.…”