The calculated absolute values of 1H and 13C chemical shifts for both families
are shown in the same ranges as for α-mangostin. By comparison the calculating 1H shift for
both γ-mangostin and garcinone D with the experimental data, it is found that there are small
errors shown in a downfield for both WP04 and B3LYP calculation. For 13C chemical shifts, the
calculated values are similar for both obtained from WC04 and B3LYP methods. Table 4 shows
the linear regression for each method calculated over a set of α-mangostin, γ-mangostin and
garcinone D. The WP04, B3LYP and WC04 methods have shown the regression slopes and
intercepts most near unity for these three molecules.