Identification and quantitative analysis of β-cryptoxanthin and β-citraurin esters in Satsuma mandarin fruit during the ripening process

- Major esters of β-cryptoxanthin and β-citraurin were identified in citrus fruits.
- β-Cryptoxanthin and β-citraurin were mainly present in esterified forms in fruits.
- CitCCD1 and CitCCD4 was specific for free β-cryptoxanthin instead of its esters.

In this study, to investigate the xanthophyll accumulation in citrus fruits, the major fatty acid esters of β-cryptoxanthin and β-citraurin were identified, and changes in their contents were investigated in two Satsuma mandarin varieties, 'Miyagawa-wase' and 'Yamashitabeni-wase', during the ripening process. The results showed that β-cryptoxanthin and β-citraurin were mainly esterified with lauric acid, myristic acid, and palmitic acid in citrus fruits. During the ripening process, β-cryptoxanthin laurate, myristate, and palmitate were accumulated gradually in the flavedos and juice sacs of the two varieties. In the flavedo of 'Yamashitabeni-wase', β-citraurin laurate, myristate, and palmitate were specifically accumulated, and their contents increased rapidly with a peak in November. In addition, functional analyses showed that CitCCD1 and CitCCD4 efficiently cleaved the free β-cryptoxanthin, but not the β-cryptoxanthin esters in vitro. The substrate specificity of CitCCDs towards free β-cryptoxanthin indicated that β-cryptoxanthin esters might be more stable than free β-cryptoxanthin in citrus fruits.