In vitro activity: Santacruzamate A inhibits the growth of HCT116 colon carcinoma cells and HuT-78 cutaneous T-cell lymphoma cells, with GI50 values of 29.4 μM and 1.4 μM, respectively. However, Santacruzamate A shows hypotoxicity to human dermal fibroblast cells (GI50 >100 μM).

Kinase Assay: The commercially availablae human recombinant enzyme and fluorogenic HDAC assay kits have used to measure percent inhibition and IC50 values of three HDAC isozymes (HDAC2, HDAC4, HDAC6). Briefly, the inhibitor is added sequentially to a black, flat-bottom 96-well microtiter plate, and the reaction mixture is incubated for 30 min at 37°C. The potent HDAC inhibitor trichostatin A (included in the assay kit) is added to the bifunctional HDAC assay developer at a final reaction concentration of 1 μM to stop deacetylation and initiate the release of the fluorophore. The reaction mixture is further incubated at room temperature for 15 min. Fluorescence is measured on a Spectra Max Gemini XPS using an excitation wavelength of 360 nm and a detection wavelength of 460 nm.

Cell Assay: HuT-78 cells incubated in Iscove’s modified Dulbecco’s medium supplemented with 20% FBS, 1% penicillin/streptomycin, and 1% L-glutamine. HCT-116 cells cultivated using McCoy’s 5A medium supplemented with 10% FBS, 1% penicillin/streptomycin, and 1% nonessential amino acids. Cells were seeded in a 96-well plate at 5000cells per well. Before treatment, the plates were incubated at 37°C, 5% CO2 for 24 h. Treatment with inhibitors were incubated in wells for 72 or 96 h using SAHA as a positive control. Antiproliferative activity was determined using a standard MTS-PMS assay.