MOLECULE

Apigenin

Apigenin, also known as chamomile or versulin, belongs to the class of organic compounds known as flavones. These are flavonoids with a structure based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one). Apigenin is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. It exists as a yellow crystalline solid that has been used to dye wool. Apigenin is abundantly found in fruits and vegetables including parsley, celery and chamomile tea. Apigenin is also one of 23 flavonoids that are found in cannabis plants (PMID: 6991645). It exhibits antiproliferative, anti-inflammatory, and antimetastatic activities through poorly defined mechanisms. Apigenin has shown significant promise as a skin cancer chemopreventive agent. In particular, apigenin inhibits the expression of involucrin (hINV), a marker of keratinocyte differentiation. Apigenin suppresses the 12-O-tetradeconylphorbol-13-acetate-dependent increase in AP1 factor expression and binding to the hINV promoter. Apigenin also inhibits the increase in promoter activity observed following overexpression of PKCdelta, constitutively active Ras, or MEKK1. The suppression of PKCdelta activity is associated with reduced phosphorylation of PKCdelta-Y311 (PMID: 16982614). Apigenin provides selective activity to promote caspase-dependent-apoptosis of leukemia cells (PMID: 16844095). Apigenin induces the expression of death receptor 5 (DR5) and synergistically acts with exogenous soluble recombinant human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to induce apoptosis in malignant tumor cells (PMID: 16648565). Apigenin is biosynthetically derived from the general phenylpropanoid pathway. The phenylpropanoid pathway starts from the aromatic amino acids L-phenylalanine or L-tyrosine, both products of the Shikimate pathway. L-phenylalanine is deaminated by phenylalanine ammonia lyase (PAL) to make cinnamate, followed by oxidation at the para position by cinnamate 4-hydroxylase (C4H) to produce p-coumarate. 4-coumarate CoA ligase (4CL) then substitutes coenzyme A (CoA) at the carboxy group of p-coumarate. Later chalcone synthase (CHS) uses consecutive condensations of three equivalents of malonyl CoA followed by aromatization to convert p-coumaroyl-CoA to chalcone. Chalcone isomerase (CHI) then isomerizes the product to close the pyrone ring to make naringenin. Finally, a flavanone synthase (FNS) enzyme oxidizes naringenin to apigenin (PMID: 12636085, 11524111)