DPP4 and neoplasm: In the anti-diabetic activity screening, (+)-isoaltholacton (4), glycoborinine (17), 2′,4′-dihydroxy-4,6′-dimethoxychalcone (24), and flavokawain A (25) simultaneously exhibited inhibition of dipeptidyl peptidase-4 (DPP4) and stimulation of the glucagon-like peptide-1 (GLP-1) secretion on the murine intestinal secretin tumor cell line (STC-1).