MAOIs are not uncommon. Just off the top of my head, tobacco plants and st. john's wort. If this is credible, and I'm not saying it is, a decent list https://www.botanical-online.com/en/medicinal-plants/depress... [0]

Anyway, they're not rare.

[0] that list looks a bit dodgy, how much maoi is in turmeric for example?