Table 3.
Main molecular ions and their fragments detected in the hydrolysates, with 4 M NaOH and 6 M HCl of OMW-2000XAD identified via HPLC-DAD-ESI-Qq-TOF (negative mode). The identification of phenolic compounds was tentatively confirmed via comparison with the data reported in the literature.
| tr (min) | [M-H]- m/z | Fragment Ions m/z | UVmax (nm) | Compound | Hydrolysate 4 M NaOH | Hydrolysate 6 M HCl | Ref. |
|---|---|---|---|---|---|---|---|
| 7.64 | 331.0026 (4.5) | 219.0523 (6.8) 153.0204 (100) 109.0287 (59.2) |
207, 217, 260, 294 | 1 *—Unknown | + | + | - |
| 10.05 | 137.0252 (100) | - | 228, 280 | 2—Tyrosol | + | - | [49] |
| 11.44 | 293.1230 (5.9) | 213.0778 (18.0) 137.0253 (100) |
224, 283, 311 | 12—Unknown | - | + | [50] |
| 12.19 | 151.0412 (100) | 109.0289 (3.8) | 200, 230, 276, 306 | 3—Vanillin | + | - | [51] |
| 13.29 | 213.0774 (44.8) | 151.0406 (100) | 207, 228, 275, 306 | 13—Elenolic acid derivative | - | + | [5] |
| 14.15 | 179.0361 (68.1) | 135.0462 (100) | 218, 323 | 4—Caffeic acid | + | + | [48] |
| 16.64 | 317.0292 (20.6) | 165.0200 (100) 121.0298 (38.5) |
209 | 5—Unknown | + | + | - |
| 19.12 | 221.0388 (4.4) | 215.0927 (12.3) 187.0176 (100) 135.0463 (75.9) |
200, 281 | 14—Unknown | - | + | - |
| 19.26 | 163.0406 (21.8) | 119.0507 (100) | 227, 310 | 6—p-Coumaric acid | + | - | [52] |
| 20.08 | 313.0741 (11.7) | 269.0867 (45.6) 179.0358 (100) 147.0113 (13.0) |
310 | Caffeic acid (dimers C-C and C-O type) | + | - | [48] |
| 20.80 | 341.1203 (58.9) | 179.0327 (100) 135.0076 (1.5) |
218, 262, 296 | 15—Caffeoyl hexoside | - | + | [53] |
| 21.07 | 193.0490 (54.0) | 178.0285 (91.0) 134.0379 (100) |
218, 238, 323 | 7—t-Ferulic acid | + | - | [52] |
| 22.42 | 225.0756 (100) | - | - | 16—Desoxyelenolic acid | - | + | [5] |
| 23.76 | 359.1110 (5.0) | 203.0354 (100) 159.0460 (84.0) |
232, 333 | 8—Syringic acid hexoside | + | - | [54] |
| 25.58 | 491.0932 (3.5) | 397.0186 (5.3) 279.0403 (26.9) 203.0289 (37.5) 170.9856 (100) |
208, 270 | 17—Unknown | - | + | - |
| 26.11 | 455.1347 (45.9) | 303.0822 (4.2) | - | Hydroxytyrosol [(2AH + A) − 2H] | - | + | [48] |
| 27.17 | 325.0701 (11.3) | 283.0618 (14.9) 197.0821 (22.9) 153.0928 (100) |
267 | 9—Unknown | + | - | - |
| 27.35 | 365.1202 (4.9) | 229.1080 (100) 199.0902 (48.2) 153.0931 (92.6) 123.0802 (35.6) |
- | 18—Dimethyl acetal of oleacein | - | + | [55] |
| 28.27 | 221.0780 (100) | 161.0246 (16.0) | 205 | 19—Unknown | - | + | - |
| 31.82 | 411.0476 (2.4) | 329.0993 (35.6) 257.0339 (100) 189.0515 (17.2) 147.0088 (3.4) |
205, 251 | 20—Unknown | - | + | - |
| 33.25 | 439.1962 (8.5) | 355.0806 (44.0) 325.0703 (79.5) 281.0812 (24.7) 159.0461 (100) |
229 | 10—Unknown | + | - | - |
| 34.54 | 651.1514 (2.9) | 325.0699 (100) 281.0811 (19.5) 237.0917 (19.2) |
- | p-Coumaric acid (tetramer) | + | - | [48] |
| 35.27 | 569.0031 (4.2) | 411.1591 (10.2) 267.0866 (30.7) 235.0603 (100) 197.0599 (8.4) |
230, 316 | 21—Unknown | - | + | - |
| 35.67 | 495.1771 (25.7) | - | - | Dihydrocaffeic acid [(2AH + A) − 2H] | + | - | [48] |
| 36.52 | 437.1101 (3.7) | 393.0810 (7.2) 301.0697 (44.2) 249.0753 (100) 225.0541 (29.9) |
226, 280 | 22—Unknown | - | + | - |
| 36.87 | 949.6636 (2.9) | 549.1617 (100) 473.0985 (2.7) 381.0401 (4.3) 287.0343 (3.0) 257.0800 (9.3) 225.0548 (2.9) |
229, 316 | 23—Unknown | - | + | - |
| 38.94 | 229.1034 (3.4) | 177.0521 (100) 141.0749 (10.4) 123.0090 (1.0) |
202, 291 | 24—3,4-Dihydroelenolic acid (demethylated) | - | + | [56] |
| 39.05 | 519.3151 (4.6) | 351.0863 (100) 295.0261 (8.4) |
230, 310 | 11—Unknown | + | - | - |
| 40.20 | 437.1204 (6.5) | 377.0486 (2.5) 257.0807 (60.0) 213.0917 (36.3) 181.0657 (100) |
227 | 25—Unknown | - | + | - |
| 41.13 | 494.0700 (7.8) | 473.0988 (7.8) 347.0385 (19.2) 263.0887 (100) 219.0811 (18.6) 171.0434 (15.6) 113.0862 (4.0) |
240, 280, 303 | 26—Unknown | - | + | - |
| 42.38 | 507.0619 (23.9) | 383.0416 (10.7) 337.0721 (7.9) 249.0702 (24.3) 205.0826 (100) |
- | 27 -Unknown | - | + | - |
| 42.66 | 257.0814 (38.8) | 225.0556 (2.5) 213.0905 (3.8) 181.0659 (100) 153.0716 (8.5) |
225 | 28—Hydroxyelenoic acid | - | + | [50] |
| 44.14 | 265.1498 (2.4) | 213.0095 (100) | 208, 231 | 29—Xanthonic acid | - | + | [50] |
Intensities relative to the base peak are given in parentheses. * Peak number assigned in the chromatograms from Figure 5a,b.