Significant differences among the antioxidant activities of the various constituents measured by FRAP, HRSA, and LPIA (P < 0.01) were observed.
Pearson's correlation coefficient was applied to evaluate the relationship between the antioxidant activity and secondary metabolite contents, including TPC, TAC, and TSC from C1 to C6 based on FRAP, HRSA, and LPIA, as shown in Table 1.
The TPC showed a significant positive correlation to FRAP and LPIA with Pearson's correlation coefficients of 0.941 and 0.639, respectively, while high positive correlations between TAC versus FRAP, HRSA, and LPIA were found with Pearson's correlation coefficients of 0.531, 0.952, and 0.88, respectively.
To further analyze the contributions of phenols and alkaloids to the antioxidant activity of maca as well as their synergistic effects, multiple linear regression was employed to construct multiple linear models with antioxidant activity (FRAP, HRSA, and LPIA) as the dependent variable (Y) and TPC and TAC as independent variables (X).