In vitro activity: Apigenin inhibits PKC by competing with adenosine triphosphate (ATP). Apigenin also reduces the level of TPA-stimulated phosphorylation of cellular proteins and inhibits TPA-induced c-jun and c-fos expression. Apigenin exhibits the reverting effect on the transformed morphology of v-H-ras transformed NIH3T3 cells. Apigenin has been shown to possess anti-mutagenic properties in a setting of nitropyrene-induced genotoxicity in Chinese hamster ovary cells. Apigenin suppresses of LPS-induced cyclooxygenase-2 and nitric oxide synthase-2 activity and expression in mouse macrophages. Apigenin has been reported to inhibit protein kinase C activity, mitogen-activated protein kinase (MAPK), transformation of C3HI mouse embryonic fibroblasts and downstream oncogenes in v-Ha-ras-transformed NIH3T3 cells. Apigenin blocks peroxisome proliferation-regulated kinase (ERK), a MAPK in isolated hepatocytes. Apigenin has further been shown to down-regulate the expression of the Na+/Ca2+-exchanger, a protein important for calcium extrusion in neonatal rat cardiac myocytes. Apigenin induces a reversible G2/M and G0/G1 arrest by inhibiting p34 (cdc2) kinase activity, accompanied by increased p53 protein stability in epidermal cells and fibroblasts. Apigenin is also effective in inhibiting TNFα-induced intracellular adhesion molecule-1 upregulation in cultured human endothelial cells. Apigenin inhibits the expression of HIF-1α and VEGF via the PI3K/Akt/p70S6K1 and HDM2/p53 pathways in human ovarian cancer cells. Apigenin inhibits differentiation by suppressing MAPK signal transduction and reducing API transcription factor level in human keratinocytes. Apigenin also inhibits proliferating of human keratinocytes.

Cell Assay: The effect of Apigenin on the viability of cells is determined by MTT assay. Near-confluent stock cultures of human gastric cancer SGC-7901 cells are harvested with 0.2% EDTA and plated at a density of 2.5×103/well in 96-well microtiter plates. After an overnight incubation to allow cell attachment, the medium is replaced by fresh medium containing different concentrations (0, 20, 40, and 80 μM) of Apigenin. Control wells receive DMSO (0.2%). Each concentration of Apigenin is repeated in four wells. After incubation for 24 h, one plate is assayed with a microplate reader at the wavelength of 570 nm. Before the assay, MTT (5 mg/mL in PBS) is added to each well and incubated for 4 h, then MTT solution is removed from the wells by aspiration. After careful removal of the medium, 0.1 mL of DMSO is added to each well, and the plate is shaken for 15 min. The data of 7 d are fed into the computer and the growth curve is drawn. The growth inhibition rate (IR) is calculated.

J Cell Biochem Suppl. 1997;28-29:39-48.; Pharm Res. 2010 Jun;27(6):962-78.