Comparison of main bioactive compounds in tea infusions with different seasonal Forsythia suspensa leaves by liquid chromatography-tandem mass spectrometry and evaluation of antioxidant activity

In the present work, five main bioactive compounds (chlorogenic acid, forsythiaside, rutin, phillyrin and phillygenin) in tea infusions prepared by brewing different seasonal Forsythia suspensa leaves were analyzed and compared using a developed liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the first time. Results showed that the highest accumulation period for the five bioactive compounds in F. suspensa leaves for tea infusions (FLTI) was the early of the vegetative cycle (April). Moreover, FLTI with April leaves exhibited considerable antioxidant capacities, IC50 values from the DPPH assay and TEAC values from ABTS and FRAP assays reached 0.143-0.171 mg/ml, 0.604-0.739 mmol Trolox/g d.m and 1.945-2.299 mmol Trolox/g d.m, respectively. Furthermore, Pearson correlation analysis testified that chlorogenic acid, forsythiaside and rutin were strongly attributed to the antioxidant activities of FLTI. Results from this study provided the comprehensive information for F. suspensa leaves collection period and the quality control for FLTI, as well as supported that FLTI could be a kind of potential antioxidant beverage as the dietary resource.

► A LC-MS/MS method is first developed to monitor five main phytochemicals in FLTI. ► April is optimal for preparation of FLTI during F. suspensa leaves vegetative cycle. ► Antioxidant activities of FLTI are first evaluated by DPPH, ABTS and FRAP assays. ► FLTI with April leaves exhibited moderate antioxidant capacities as compared to VC. ► FLTI can be exploited as a potential antioxidant beverage for health-promoting.