Weak K-amplitudes in the chiral and 1Nc-expansions

It is shown that there exist symmetry constraints for non-leptonic weak amplitudes which emerge when the 1Nc-expansion restricted to the leading and next-to-leading approximations only is systematically combined with χPT limited to the lowest non-trivial order. We discuss these constraints for the couplings g8 and g27 of ΔS = 1 transitions and the BK-parameter of K0-K0 mixing.