Asian Journal of Medical Sciences 3(2): 79-83, 2011. 
Antidepressant Effects of Noni Fruit and its Active Principals. 
Deng S., West B.J.

Noni fruit extracts inhibited monoamine oxidase (MAO) A and B in vitro. Phytochemicals in the most active extract included kaempferol and quercetin, as well as (+)-3,4,3′,4′-tetrahydro-9,7’α-epoxylignan-7α,9′-lactone, which were found to be potent MAO-A and B inhibitors. (original abstract available at