In vitro activity: Griseofulvin is active against dermatophytes of different species in the genera Microsporum, Trichophyton and Epidermophyton. Other fungi such as Scopulariopsis brevicaulis and Hendersomula toruloidea are insensitive. Griseofulvin has little or no effect against yeasts and bacteria. The minimum inhibitory concentration of Griseofulvin tested in vitro against various dermatophytes ranges between 0.14 and 0.6 μg/mL. Main effect of Griseofulvin on cell mitosis is disorganization of the spindle microtubules. Griseofulvin is also able to induce structural chromosomal aberrations in mammalian cells. Griseofulvin inhibits the viability of human colon adenocarcinoma cells COLO 205 and HT 29, hepatoma cells Hep G2 and Hep 3B, leukemia cells HL 60, and normal keratinocytes (#76 KhGH) with IC50s of ~1 and ~5 μM, 5 and 5 μM, 1 μM, and 50 μM, respectively after a 30 hr incubation,. Griseofulvin (20 μM) induces a marked presence of abnormal mitotic spindle formation with mono-, bi-, and tripolar spindles of varying lengths in HT 29 cells, and causes G2/M cell cycle arrest at 24h through elevation of cyclin B1/cdc2 kinase activity and down-regulation of myt-1 protein expression. Griseofulvin is able to induce apoptosis of HT 29 cells via caspase3 activation, Bcl-2 hyperphosphorylation and inhibition of the normal function of Bcl-2 associated with Bax.

Cell Assay: The cells (5× 103/mL) are incubated in triplicate in a 96-well plate in the presence or absence of indicated concentration of Griseofulvin in a final volume of 0.2 mL for different time intervals at 37 ℃. Thereafter, 20 μL MTT solution (5 mg/mL in PBS) is added to each well. After a 2-hour incubation at 37 ℃, 0.1 mL lysis buffer (20% SDS, 50% dimethylformamide) is added, incubation is continued overnight at 37 ℃, and then the optical density at 570 nm is measured by plate reader.

Mutat Res. 1988 Mar;195(2):91-126; Int J Cancer. 2001 Feb 1;91(3):393-401.