Effects of microwave cooking on carotenoids, phenolic compounds and antioxidant activity of Cichorium intybus L. (chicory) leaves

This study evaluated for the first time the effects of microwave cooking (MWC) on phenolic, carotenoids, pigment profiles and antioxidant activity of chicory (Cichorium intybus L.) leaves grown on fresh water. The phenolic compounds, carotenoids and pigments in the leaves were extracted, analyzed and quantified using reversed-phase HPLC-DAD. Lipid peroxidation, total phenolic contents (TPC), total flavonoid contents (TFC) and radical scavenging activity (RSA) were analyzed. Results showed that 18 phenolic compounds were identified and quantified in chicory leaves. The phenolic compounds were p-hydroxybenzoic acid, quinic acid, 3-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, coumaric acid, caftaric acid, chicoric acid, 3,4-di-O-caffeoylquinic acid, caffeoyl hexose, quercetin-3-feruloyl-sophoroside, 4-feruloyl quinic acid, quercetin-3-glucoside, quercetin-di-glucoside, kaempferol-3-sophoroside, luteolin-7-O-glucoside, quercetin-3-O-rutinoside, and kaempferol-3-O-glucoside. A significant increase was observed in most of the phenolic compounds during MWC. Six carotenoids and 10 pigments were also identified and quantified. All-E-lutein, all-E-β-carotene, all-E-neoxanthin and all-E-violaxanthin were the major carotenoids. A significant increase occurred in the amount of carotenoids during MWC. Among the pigments, 13-hydroxy-chlorophyll b, chlorophyll a, chlorophyll bʹ, hydroxy-chlorophyll a, and chlorophyll b were present in high amounts. Pigments contents dropped with MWC. Lipid peroxidation, TPC, and TFC were significantly increased with MWC. RSA was either increased or remained unchanged. In conclusion, cooking of chicory leaves or its pre-treatment with microwave in food industries enhanced important bioactive substances for consumer health.