Table 2.
Phenolic compounds detected in grape stems extracts: Chemical structure, retention time (RT), and maximum absorption wavelength (λmax).
| Phenolic Compound | Chemical Structure | RT (min) | λmax (nm) |
|---|---|---|---|
| Gallic acid |
|
5.9 ± 0.1 | 272 |
| (+)-Catechin |
|
16.3 ± 0.4 | 279 |
| Quercetin |
|
41.6 ± 0.3 | 369 |
| Quercetin-3-glucuronide * |
|
28.8 ± 0.3 | 355 |
| Quercetin-3-glucoside * |
|
28.2 ± 0.3 | 354 |
| Malvidin-3-glucoside |
|
22.5 ± 0.4 | 526 |
| Anthocyanidin | unknown | 35.8 ± 0.4 | 533 |
| trans-Resveratrol |
|
37.8 ± 0.3 | 306 |
| trans-ε-Viniferin |
|
44.1 ± 0.2 | 324 |
* Both quercetin-3-glucoside and quercetin-3-glucuronide show similar spectra and retention times, so it was not possible to differentiate them in samples.