TABLE 2.
Binding affinities (Ki) of kratom alkaloids toward opioid (OR), adrenergic (α), and serotonergic (5-HT) receptors
| Receptor | Mitragynine | 7-Hydroxy-Mitragynine | Speciogynine | Paynantheine | Speciociliatine | Corynantheidine | Corynoxeine | Corynoxine B | Speciofoline |
|---|---|---|---|---|---|---|---|---|---|
| Ki ± S.E.M. (nM) | |||||||||
| μOR | 238 ± 28 233 ± 48 161 ± 10 |
16 ± 1 47 ± 18 7.16 ± 0.94 |
728 ± 61 | 410 ± 152 | 54.5 ± 4.4 560 ± 168 |
118 ± 12 | 16.3 ± 1.4 >10,000 |
109.8 ± 8.1 1600 |
>10,000 |
| κOR | 482 ± 29 772 ± 207 198 ± 30 |
113 ± 37 188 ± 38 74.1 ± 7.8 |
3200 ± 360 116 ± 36 |
2560 ± 370 | 116 ± 36 329 ± 112 |
1910 ± 50 | >10,000 | >10,000 | >10,000 |
| δOR | >10,000 | 137 ± 21 219 ± 41 |
>10,000 | >10,000 | >10,000 | >10,000 | >10,000 | 7600 | >10,000 |
| 5-HT1A | 5880 ± 828 | — | 95.5 ± 34.7 | 71.8 ± 13.2 | — | — | — | — | — |
| 5-HT7A | >10,000 | — | 1600 ± 82 | 870 ± 72 | — | — | — | — | — |
| 5-HT2A | 5010 ± 1150 | — | 1320 ± 365 | 815 ± 192 | — | — | — | — | — |
| 5-HT2B | 1260 ± 138 | — | 23.0 ± 5.7 | 20.0 ± 2.8 | — | — | — | — | — |
| 5-HT2C | >10,000 | — | 5430 ± 922 | 1770 ± 417 | — | — | — | — | — |
| α-1A | 1340 ± 100 | — | — | — | — | >10,000 | — | — | — |
| α-1B | 4770 ± 120 | — | — | — | — | >10,000 | — | — | — |
| α-1D | 5480 ± 540 | — | — | — | — | 41.7 ± 4.7 | — | — | — |
| α-2A | 4720 ± 120 | >10,000 | — | — | — | >10,000 | — | — | — |
| α-2B | 9290 ± 30 | >10,000 | — | — | — | >10,000 | — | — | — |
| α-2C | 2320 ± 140 | >10,000 | — | — | — | >10,000 | — | — | — |
—, information not available.