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Composition analysis of carotenoids and phenolic compounds and antioxidant activity from hibiscus calyces (Hibiscus sabdariffa L.) by HPLC-DAD-MS/MS.

INTRODUCTION
The hibiscus flower has received increasing interest because it contains high levels of bioactive compounds with remarkable functional properties. To the best of our knowledge, for the first time a detailed description of the carotenoid composition of hibiscus calyces is reported.


OBJECTIVES
Identification and quantification of carotenoids, phenolic compounds and antioxidant activity from hibiscus calyces.


MATERIAL AND METHODS
The composition of the carotenoids and phenolic compounds from hibiscus calyces was determined by high-performance liquid chromatography coupled to a diode array detector and tandem mass spectrometry (HPLC-DAD-MS/MS). Antioxidant activity was assessed using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging and hydroxyl radicals scavenging assays.


RESULTS
Twenty-one carotenoids were found and from these compounds 15 were identified or tentatively identified. The major carotenoids were all-trans-lutein (316.43 ± 19.92 μg/100 g) and all-trans-β-carotene (147.76 ± 5.59 μg/100 g). Twenty phenolic compounds were found, from which 14 compounds were identified or tentatively identified. The major phenolic compounds were delphinidin 3-sambubioside (218.17 ± 12.69 mg/100 g) and 3-caffeoylquinic acid (79.22 ± 7.01 mg/100 g), representing almost 60% (w/w) of the total phenolic compounds from hibiscus calyces. The hibiscus presented low vitamin A activity, measure as retinol activity equivalent (13.52 μg/100 g). The scavenging activity of ABTS and hydroxyl radicals were 7.8 μmol Trolox equivalent/g and 81%, respectively.


CONCLUSION
In this study we have shown that the hibiscus calyces can be considered as a food rich in lutein, chlorogenic acids and anthocyanins (delphinidin 3-sambubioside).