On-line HPLC-ABTS screening and HPLC-DAD-MS/MS identification of free radical scavengers in Gardenia (Gardenia jasminoides Ellis) fruit extracts

Gardenia jasminoides Ellis is a folk medicine for pharmacological activities in China. In this study, on-line HPLC-ABTS and HPLC-DAD-MS/MS analyses were applied to screen and identify free radical scavengers in gardenia fruit extracts (GFE). Nine compounds were identified (3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, 4,5-dicaffeoylquinic acid, quercetin-3-rutinoside, crocetin di(β-gentiobiosyl) ester, and geniposide). 3-Caffeoylquinic acid and 4-caffeoylquinic acid were firstly found in GFE. Caffeoylquinic acids, dicaffeoylquinic acids, and 4-sinapoyl-5-caffeoylquinic acid were the dominant free radical scavengers in GFE, and their Trolox equivalent antioxidant capacities (TEAC) were determined. 3,5-Dicaffeoylquinic acid was the most potent antioxidant with TEAC value of 1.1 mM. In contrast, crocetin di(β-gentiobiosyl) ester and geniposide showed little ABTS+ scavenging activity.