Non-heme dioxygenase catalyzes atypical oxidations of 6,7-bicyclic systems to form the 6,6-quinolone core of viridicatin-type fungal alkaloids.

The 6,6-quinolone scaffold of the viridicatin-type of fungal alkaloids are found in various quinolone alkaloids which often exhibit useful biological activities. Thus, it is of interest to identify viridicatin-forming enzymes and understand how such alkaloids are biosynthesized. Here an Aspergillal gene cluster responsible for the biosynthesis of 4'-methoxyviridicatin was identified.

Indole alkaloids of a Thai medicinal herb, Mitragyna speciosa, that has opioid agonistic effect in guinea-pig ileum.

Recently, we found that mitragynine, a major constituent of Mitragyna speciosa, has an opioid agonistic activity, but its weak potency could not explain the opium-like effect of this plant. In the present study, bioassay-guided fractionation of the crude extract of the leaves of M. speciosa was carried out to search for potent opioid agonists other than mitragynine.

Studies on the synthesis and opioid agonistic activities of mitragynine-related indole alkaloids: discovery of opioid agonists structurally different from other opioid ligands.

Mitragynine (1) is a major alkaloidal component in the Thai traditional medicinal herb, Mitragyna speciosa, and has been proven to exhibit analgesic activity mediated by opioid receptors. By utilizing this natural product as a lead compound, synthesis of some derivatives, evaluations of the structure-activity relationship, and surveys of the intrinsic activities and potencies on opioid receptors were performed with guinea pig ileum. The affinities of some compounds for mu-, delta-, and kappa-receptors were determined in a receptor binding assay.