Carotenoid composition of strawberry tree (Arbutus unedo L.) fruits.

The carotenoid composition of strawberry tree (Arbutus unedo) fruits has been characterised in detail and quantified for the first time. According to the total carotenoid content (over 340 μg/g dw), mature strawberry tree berries can be classified as fruits with very high carotenoid content (>20 μg/g dw). (all-E)-Violaxanthin and 9Z-violaxanthin were found to be the major carotenoid pigments, accounting for more than 60%, responsible for the bright colour of the flesh of ripe fruits. In addition other 5,6-epoxide carotenoids, such as (all-E)-neoxanthin, (9'Z)-neoxanthin (all-E)-antheraxanthin and lutein 5,6-epoxide, together with (all-E)-lutein, (all-E)-zeaxanthin and (all-E)-β-carotene were found at high levels (>5-20 μg/g dw). The LC-MS (APCI+) analysis of the xanthophyll fraction in their native state (direct extract) revealed that most of them (>90%) were totally esterified with saturated fatty acids (capric, lauric, myristic, palmitic and stearic). Monoesters, homodiesters and heterodiesters of (all-E)-violaxanthin and 9Z-violaxanthin were the major pigments.