PCAC relation for Dstar -> D axial form factors

A relation among the form factors of $<D\mid A_{\mu }\mid D^{\ast }>$ at $q^2\to 0$ is derived. It is verified to lowest order in both the $1\mathrm{/}{m}_c$ expansion and the expansion in number of derivatives using the effective lagrangian that incorporates the heavy quark symmetries for the b and c quarks, and the chiral symmetry for the u, d, s quarks.