  We discuss the truncation of low energy effective action of QCD below the
chiral symmetry breaking (CSB) scale, including all operators of dimensionality
less or equal to 6 which can be built with quark and chiral fields. We perform
its bosonization in the scalar, pseudoscalar, vector and axial-vector channels
in the large-N_c and leading-log approximation. Constraints on the coefficients
of the effective lagrangian are derived from the requirement of Chiral Symmetry
Restoration (CSR) at energies above the CSB scale in the scalar-pseudoscalar
and vector-axial-vector channels, from matching to QCD at intermediate scales,
and by fitting some hadronic observables. In this truncation two types of
pseudoscalar states (massless pions and massive Pi'-mesons), as well as a
scalar, vector and axial-vector one arise as a consequence of dynamical chiral
symmetry breaking. Their masses and coupling constants as well as a number of
chiral structural constants are derived. A reasonable fit of all parameters
supports a relatively heavy scalar meson (quarkonium) with the mass \sim 1 GeV
and a small value of axial pion-quark coupling constant g_A \simeq 0.55.
