Baicalein is a cell-permeable flavone, originally isolated from the roots of Scutellaria baicalensis, that inhibits cellular Ca2+uptake, calcium mobilization, and adjuvant-induced arthritis. Baicalein has been shown to inhibit platelet 5-LO (5-lipoxygenase) and 12-LO (12-lipoxygenases) and reverse transcriptase. Baicalein reduces leukotriene biosynthesis and inhibits the release of lysosomal enzymes. Baicalein is a potent anti-inflammatory and anti-tumor agent, and it blocks PREP (prolyl oligopeptidase). Baicalein induces the S-phase arrest and apoptosis in proliferation of human lung squamous carcinoma CH27 cells. The declining expression of cdk1, cdk2, cyclin D2 and cyclin A by Baicalein resulted in the G1 and G2 cell cycle arrest in C6 rat glioma cells. Baicalein has anti-thrombotic, antiproliferative and anti-mitogenic effects. Baicalein inhibits protein tyrosine kinase in leukemia (CEM) cells and PMA-stimulated PKC (protein kinase C). Baicalein is an inhibitor of 15-LO and CYP2C9.