Baicalein (5,6,7-Trihydroxyflavone) is a xanthine oxidase inhibitor.

Baicalein effectively inhibits T cell proliferation and cytokine secretion in response to mitogens in vitro. It has been observed that pre-treatment with baicalein markedly reduces both Con A or anti-CD3/CD28 mAb-induced cell proliferation and cytokine release at a concentration of 25 μM. Additionally, baicalein initiates NF-κB DNA binding while concurrently inhibiting nuclear thioredoxin activity. Furthermore, baicalein hampers the proliferation, migration, and invasion of MDA-MB-231 cells in both a time- and dose-dependent manner, significantly lowering SATB1 expression in these cells. It also diminishes the expression of Wnt1 and β-catenin proteins, along with the transcription of Wnt/β-catenin-regulated genes.

Baicalein effectively reduces graft versus host disease induction without hindering T-cell homeostatic proliferation in mice, demonstrating its significant anti-inflammatory properties in vivo[2]. Further, in rats, baicalein administration guards against elevated heart to body weight ratios, increases in plasma brain natriuretic peptide levels, intraventricular septum thickness, and myocardial collagen volume in the left ventricle (all P<0.05, respectively). Its antifibrotic action is underscored by the reduced expression of pro-collagens I and III in the left ventricle, alongside diminished expression of 12-lipoxygenase, and lowered expression and activity of matrix metallopeptidase 9 and extracellular signal-regulated kinases, thus demonstrating baicalein's capability to inhibit cardiac fibrosis in hypertensive rats[4].

MTT assay is conducted to evaluate the effect of baicalein on proliferation of breast cancer cells. MDA-MB-231 cells are routinely digested, collected, and then seeded in 96-well plates at a density of 8×103 cells/well. After incubation for 12-24 hours, cells are treated with 0, 20, 40, 60, 80, 100, and 120 μM baicalein according to their experimental grouping and then incubated at 37°C for 24, 48, and 72 hours[3].