Baccatin III is an isolate of the Pacific yew tree (Taxus brevifolia) and related species. Baccatin III is the precursor to paclitaxel/ taxol. Antileukaemic and antitumor agent, Baccatin III, binds to tubules when they are assembled in the cell and stabilizes the polymerized form of tubules so that they remain assembled even under conditions in which microtubules dissociate into tubulin subunits. Baccatin III is also an inducer of apoptosis and shows antitumor properties in vitro. Baccatin III exerts anti-tumor immunomodulatory activity in very low doses (0.05-0.5mg/kg), although it is regarded as an inactive derivative of paclitaxel. Oral administration of Baccatin III significantly reduced the growth of tumors induced by engrafting BALB/c mice with either 4 T1 mammary carcinoma or CT26 colon cancer cells. Baccatin III reduced tumor progression by inhibiting the accumulation and suppressive function of MDSCs. Baccatin III inhibited cell proliferation of a number of cancer cell lines. The cytotoxic activity exhibited by fungal taxol and Baccatin III involves the same mechanism, dependent on caspase-10 and membrane potential loss of mitochondria, with taxol having far greater cytotoxic potential.