How do you define "a LOT"? the only estimate I can find says there's 210mcg/L of beta-carbolines. Mainly harman and norharman, which have a binding affinity for MAO-A of 220nM and 2200nM respectively(lower is more potent). Not earth-shatteringly potent. These compounds have a fairly short half-life and they're reversible.
Doesn't seem to be anywhere close to the potency of MAO inhibition used in psychiatric or entheogenic contexts. I'd be reluctant to attribute too many noticable effects to them.