  We study perturbative unitarity constraints on generic Yukawa interactions
where the involved fields have arbitrary quantum numbers under an $\prod_i
SU(N_i) \otimes U(1)$ group. We derive compact expressions for the bounds on
the Yukawa couplings for the cases where the fields transform under the
trivial, fundamental or adjoint representation of the various $SU(N)$ factors.
We apply our results to specific models formulated to explain the anomalous
measurements of $(g-2)_\mu$ and of the charged- and neutral-current decays of
the $B$ mesons. We show that, while these models can generally still explain
the observed experimental values, the required Yukawa couplings are pushed at
the edge of the perturbative regime.
