Abstract: In nature, more than 90% of lycopene exists in all-trans form, but cis-lycopene in human blood and tissues accounts for more than 50% of total lycopene, and the proportion of cis-lycopene in prostate tissue was 90%. Numerous studies have shown that cis-lycopene has higher bioavailability than trans-lycopene, and thus has higher nutritional value and potential for development and utilization. Therefore, the properties and structures of lycopene isomers, the effect of extraction methods on the isomerization of lycopene, the types of isomerization (thermal isomerization, photoisomerization, etc.) and the physiological functions of cis-lycopene are reviewed in this paper. The mechanisms of different isomerization processes are expounded, and the advantages and disadvantages of each isomerization process are summarized. It is hoped that this review will provide a theoretical basis for further research on lycopene isomerization and provide scientific guidance for the production of lycopene with high proportion of cis-isomers.

Key words: lycopene; cis-isomers; isomerization; function; mechanism; stability