The contribution of the direct radiative capture of protons by ¹⁰B and ²⁴Mg nuclei at low energies to the astrophysical S-factors in the reactions ₁₀B(p,γ)¹¹C and ²⁴Mg(p,γ)²⁵Al have been calculated within the R-matrix formalism by using empirical proton asymptotical normalization coefficients (ANC). The ANCs for bound proton configurations {¹⁰B+p} and {²⁴Mg+p} were obtained from the analysis of the reactions (³He, d). The ANCs were also estimated from the values of the neutron ANCs in the mirror nucleus ²⁵Mg following the suggestion that the neutron and the proton in the mirror states have equivalent nuclear potentials. It has been found that the S-factor for the reaction ¹⁰B(p,γ)¹¹C extrapolated to zero energy contributes ~100 keV b to the radiative capture to the ground state of ¹¹C. For the reaction ²⁴Mg(p,γ)²⁵Al the value S(0) gives 58 keV b with a direct capture contribution of 41 keV b.