Table 3.

Percent Displacement of Radioligands by Selected M. speciosa Alkaloids at Opioid Receptor Subtypes in a Screening Profile^a

M. speciosa alkaloid concentration	δ-opioid	κ-opioid	μ-opioid
corynoxine (1)
100 nM	−3.9	3.8	80.1
10 000 nM	73.8	75.3	97.8
corynoxine B (2)
100 nM	−4.4	4.5	45.4
10 000 nM	65.5	51.8	94.4
isospeciofoline (3)
100 nM	0.0	0.1	13.1
10 000 nM	27.1	37.3	83.3
mitragynine oxindole B (4)
100 nM	10.4	5.0	7.3
10 000 nM	87.1	23.0	66.5
speciociliatine N(4)-oxide (10)
100 nM	5.1	6.6	10.5
10 000 nM	53.5	80.9	84.6

^aFor subtype δ, human recombinant Chem-1 (RBL) cells. [³H]DADLE at 0.5 nM was used as a ligand. Naltrexone (10 μM) was used as a nonspecific binder, with 60 min incubation. For subtype κ, human recombinant RBL cells. [³H]U69,593 at 0.5 nM was used as a ligand. Naloxone (10 μM) was used as a nonspecific binder, with 60 min incubation. For subtype μ, human recombinant HEK-293 cells. [³H]DAMGO at 0.5 nM was used as a ligand. Naloxone (10 μM) was used as a nonspecific binder, with 120 min incubation. All assays were performed at room temperature.

^bBold font in body of the table represents >50% displacement.