A Comprehensive Database of Phenolic Acids in Plant Foods: Soluble Free, Soluble Conjugated, and Insoluble-Bound Forms
Description
We developed a database on the contents of soluble free, soluble conjugated and insoluble-bound forms of 8 individual phenolic acids across 322 plant foods and beverages.
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The content of phenolic acids was measured using a WATERS 2695 HPLC system equipped with an electrochemical detector (ECD) . The column was an Agilent ZORBAX-Eclipse SB-C18 (150 mm_4.6 mm, 5.0 μm). The mobile phase was methanol (A) and 1% aqueous acetic acid (B) (v/v) with a linear gradient elution as follows: 5–15% A from 0 to 10 min, remaining at 15% A at 10–20 min, 15–17% A from 20 to 25 min, 17–30% A from 25–30 min, 30–40% A from 30 to 50 min. The flow rate was maintained at 1.0 mL/min, and the column was operated at 30 °C. The injection volume was 10 μL. The working voltage of electrochemical detector was maintained at 0.9 V. Ten minutes were required between the injection of the two samples for re-equilibration. Calibration curves of 8 phenolic acid standards varied from 0.05 to 50 μg/mL were constructed by plotting the peak areas against concentrations. These curves showed good linearity within the range of 0.05-50 μg/mL (R2 > 0.9991). The limits of detection (LOD) and limits of quantification (LOQ) were 0.006–0.413 and 0.044–1.348 μg/mL (signal-to-noise approach defines LOD at 3:1 and LOQ at 10:1 ratios), respectively. The intra-day and inter-day precisions were evaluated by injecting 10 μg/mL standard solutions on the same day for three times and on three consecutive days. The intra-day and inter-day relative standard deviation (RSD) values (%) was 3.08 to 6.64, and 3.90 to 8.05, respectively. The RSDs of all analytes were generally stable, as the RSD was 1.02% to 4.05% when sample solutions were stored for three, six and twelve months at -80°C. The recovery rate was determined by spiking purple cabbage samples with 8 phenolic acid standards. Recovery rates were calculated by formula: recovery (%) = (Amount determined-original amount)/Amount spiked × 100 %. Recoveries of the 8 analytes ranged from 88.04 % to 106.72 %, with RSD values in the range of 0.32–4.16 %.
Institutions
- Sun Yat-Sen UniversityGuangdong, Guangzhou