Citropten, a coumarin isolated from bergamot oil, has antiproliferative effects on human melanoma cell line A2058.

Assay of protein kinase C (PKC) and cAMP-dependent protein kinase (PKA) activities.: PKC and PKA activities are detected. Briefly, 5 mL of PKC or PKA is mixed with 5 mL of lipid preparation containing 100 mM phorbol 12-myristate 13-acetate, 2.8 mg/mL phosphatidyl serine, and Triton X-100 mixed micelles for PKC assay or 5 mL of 40 mM cAMP in 50 mM Tris-HCl, pH 7.5, for PKA assay, and 5 mL of daphnetin. The reaction is started by adding 10 mL of PKC substrate solution containing 250 mM acetylated myelin basic protein, 100 mM ATP, 5 mM CaCl2, 10 mM MgCl2, 20 mM Tris-HCl, pH 7.5, or 10 mL of PKA substrate solution containing 200 mM Kemptide, 400 mM ATP, 40 mM MgCl2, 1 mg/mL BSA, 50 mM Tris-HCl, pH 7.5, and 20-25 mCi/mL[g-32P] ATP. After incubation at 25 °C for 5 minutes, 20 mL of each mixture is spotted on a piece of phosphocellulose disc which is immediately put into 1% H3PO4. After free [g-32P] ATP on the discs is removed, the peptide-incorporated 32P on the discs is counted in a scintillation counte