Content and isomeric ratio of lycopene in food and human blood plasma

Lycopene content up to 520 mu g g(-1) was measured in a number of tomato-based foodstuffs and meals. (all-E)-Lycopene was the predominant geometrical isomer but varied from 96% to 35% of total lycopene. (5Z)-Lycopene ranged from 4% to 27%. The proportion of (9Z)-lycopene fluctuated between <1% and 14%. (13Z)-Lycopene and (15Z)-lycopene ranged (together) from <1% to 7% and the sum of the other (Z)-isomers varied between <1% and 22% of total lycopene. It was shown that, during preparation of meals, lycopene undergoes (E/Z)-isomerisation, increasing the portion of (Z)-isomers. Compared to food, in human blood plasma the isomeric ratio of lycopene was found to be shifted in favour of the (Z)-isomer fraction, with (5Z)-lycopene as the predominant non-(all-E) component. (C) 1997 Elsevier Science Ltd.