  Using a hybrid kinetic magnetohydrodynamic formalism incorporating the
effects of pressure anisotropy, we simulate the evolution of a turbulent
collisionless plasma in six different models covering the sub/super-sonic and
sub/super-Alfv\'enic regimes. Based on the power spectrum of the simulated
magnetic field, we compute the particle diffusion coefficients for protons with
kinetic energy in the $50-500$ MeV range, and compare them to those obtained
within standard magnetohydrodynamics. Our results show that the differences in
the statistical properties of the magnetic field, generated by pressure
anisotropy and its associated kinetic instabilities, have an appreciable impact
on the diffusion coefficients of energetic protons. Moreover, the values of the
diffusion coefficients that we obtain within each of the six models considered
vary significantly.
