Table 1.
Linearity of standard calibration curves for various phenolic acid standards as determined by HPLC-UV.
| Phenolic acid | Calibration curve range (µg/mL) | Regression equation | R2 | Retention time (min) | Area (y) (mAU*s) |
Concentration (x, µg/g) |
|---|---|---|---|---|---|---|
| Gallic | 1.56–25 | y= 57.342x − 0.3129 | R2 = 1 | 2.267 | 39,544.9 | 689.64 |
| Hydroxycinnamic | 1.56–25 | y = 33.738x − 2.0438 | R2 = 1 | 6.256 | 517,169.8 | 15329 |
| Chlorogenic | 3.13–25 | y = 4.4916x − 0.3016 | R2 = 1 | 6.914 | 433,190.5 | 9644.45 |
| Caffeic | 1.56–25 | y = 18.791x − 0.728 | R2 = 1 | 8.387 | 19,381.3 | 1031.45 |
| Vanillic | 1.56–100 | y = 36.364x − 0.3407 | R2 = 1 | 8.567 | 40,229.6 | 1106.31 |
| Syringic | 1.56–100 | y = 58.995x − 3.4366 | R2 = 1 | 9.496 | 61,044.9 | 1038.81 |
| Protocatechuic | 6.25–50 | y = 57.727x − 8.409 | R2 = 0.9999 | 11.848 | 858,296.3 | 1486.83 |
| p-Coumaric | 1.56–100 | y = 58.331x − 4.9255 | R2 = 1 | 12.055 | 54,838.8 | 940.22 |
| Ferulic | 1.56–12.5 | y = 13.942x − 0.6618 | R2 = 0.9999 | 13.207 | 20,491.5 | 1469.82 |
Where y = Area (mAU*s), x = Concentration (µg/mL), R2 is the regression coefficient and the calibration curve range is in (µg/g), respectively.