An analytical method for the determination of flavonoids in Houttuynia cordata Thunb. by UPLC-TQ-MS and analysis of its antioxidant activity

Houttuynia cordata Thunb. (H.cordata), as a traditional Chinese medicinal herb and food, has been used to treat various diseases because of rich content in flavonoids. Here, an ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry (UPLC-TQ-MS/MS) method was proposed for the determination of flavonoids profiling in H.cordata. Single factor experiment and response surface methodology were used to optimize the pretreatment process of H.cordata samples. The optimal conditions were as follows: ultrasonic temperature: room temperature (25 °C); ultrasonic time: 5 min; solid-liquid ratio: 1:40 and concentration of ethanol: 60%. The method showed the good linearity (r ≥ 0.9855), the satisfactory intra-day (RSD%≤10.94%) and inter-day precision (RSD% ≤ 11.2%) and low limit of quantification (< 0.01 µg/mL). The content of flavonoids in flowers and leaves was much higher than in roots and stems. The flavonoids in the leaves of H.cordata from Chongqing was the highest (9.22 mg/g), and that in the flowers of H.cordata from Hubei province was the highest (6.69 mg/g). In addition, the antioxidant activity of the extracts of H.cordata was evaluated using the scavenging effect of the extracts on five free radicals and the iron ion reducing ability. The best antioxidant activity was observed in scavenging DPPH free radicals with EC₅₀ value of 295.16 µg/mL. The scavenging of ABTS•+ free radicals and PTIO• free radicals was also effective with EC₅₀ values of 818.82 µg/mL and 685.43 685.43 µg/mL, respectively. Thus, this study will be helpful to the development and utilization of flavonoids from H.cordata in food and pharmaceutical industries.