We present the inhibitory properties of the R. pompana anthocyanin fraction (RPAF) and its major constituents on alpha-glucosidase (AG), pancreatic lipase (PL), HMG-CoA reductase, and ornithine decarboxylase (ODC). The effect of RPAF was also evaluated in ICR male mice subjected to oral glucose tolerance test (OGTT) and hypercaloric/atherogenic diet for 30 days. RP-HPLC/MS profiling revealed that RPAF contained five major anthocyanins and induced slight inhibition on PL and HMG-CoA reductase (IC50, 245–338 μg mL−1) whereas strong activity on AG and ODC (IC50, 130–133 μg mL−1) was observed. Kinetic studies and molecular docking with pelargonidin-3-O-rutinoside (P3R) on ODC, revealed changes in Km (0.9514–0.9746 mM) and Vmax (1.96–2.32 μmol mg−1 min−1) suggesting mixed inhibition and molecular interaction with two active sites of ODC. P3R showed antiproliferative activity (IC50, 46.5 μM) and decreased polyamine accumulation in DLD-1 cells.