curcumin and hispolon

The antiproliferative action of hispolon derivatives is stronger than that of related curcumin against several tumor cell lines. Hispolon size, smaller than curcumin, fits better than curcumin into the active site of HDAC6, an enzyme involved in deacetylation of lysine residues. HDACs are considered potential targets for tumor drug discovery and hydroxamates are known inhibitors of HDACs. One of them, SAHA (Vorinostat) is used in clinical studies. Investigations into possible mechanisms for hispolon derivatives active against the HCT116 colon tumor cell line are done after examining the structural results obtained from hispolon X-ray crystal structures as well as performing associated computational docking and Density Functional Theory techniques on HDAC6. These studies show preference for the HDAC6 active site by chelating the Zn center, in contrast with other ineffective hispolon derivatives, that establish only a single bond to the metal center. Structure activity relationships make clear that hydrogenation of the hispolon bridge also leads to single bond (non chelate) hispolon-Zn binding, and consistently nullifies the antiproliferative action against HCT116 tumor.

Topics: Antineoplastic Agents; Catechols; Cell Proliferation; Cell Survival; Crystallography, X-Ray; Density Functional Theory; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; HCT116 Cells; Histone Deacetylase Inhibitors; Histone Deacetylases; Humans; Models, Molecular; Molecular Structure; Structure-Activity Relationship

A series of 20 hispolons/dihydrohispolons were synthesized and characterized by spectral data. These compounds were subjected to in vitro antitubercular activity screening against Mycobacterium tuberculosis (H37Rv) strain. The synthesized compounds showed varied antitubercular activity ranging from 100 to 1.6μg/mL. Among the screened compounds, four compounds (H1, H2, H3 and H15) have shown moderate activity with MIC 25μg/mL. Potent activities were observed for the dihydrohispolon derivative H14 (MIC 1.6μg/mL) followed by H13 (6.25μg/mL) and H17 (12.5μg/mL), H19 (3.125μg/ML). Docking simulations gave good insights on the possible interactions between the tested compounds and β-keto acyl synthase enzyme (mtbFabH). Drug-inhibitor combination studies showed no synergism with the drugs targeting mycolic acid biosynthesis (isoniazid, ethambutol and thiolactomycin, a specific inhibitor of KAS-B enzyme) but showed significant synergism with other drugs including rifampicin and ciprofloxacin ascertaining the drug target for hispolons as inhibition of mycolic acid biosynthesis, probably via mtbFabH.

Topics: Antitubercular Agents; Catechols; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Microbial Sensitivity Tests; Molecular Docking Simulation; Molecular Structure; Mycobacterium tuberculosis; Structure-Activity Relationship

Curcumin, a component of turmeric (Curcuma longa), exhibits anti-inflammatory and anti-proliferative activities through the generation of reactive oxygen species (ROS). Curcumin (diferuloylmethane) contains two hydroxyl, two methoxy and two phenyl groups but how these groups contribute to its activity is poorly understood. We synthesized analogues that varied in inclusion of these groups and compared their activity. We found that bisdemethylcurcumin (BDC) was more potent than curcumin as an anti-inflammatory agent as indicated by suppression of TNF-induced NF-kappaB activation, more potent as an anti-proliferative agent, and more potent in inducing ROS. Hispolon, which lacks one aromatic unit in relation to curcumin, also exhibited enhanced anti-inflammatory and anti-proliferative activities. When synthetic curcumin (Cur-S) was compared with bisdemethylcurcumin (BDC), hispolon, hispolon methyl ether (HME), dehydroxy hispolon (DH), hydroxy hispolon (HH), methoxy hispolon methyl ether (MHME), and methoxy hispolon (MH), we found that following order of anti-inflammatory activity: BDC=Hispolon>HME>HH>Cur-S>MHME>MH>DH; for anti-proliferative: Hispolon>BDC>MHME>Cur-S>MH>HME=HH>DH; and for prooxidant: BDC>Cur-S=MHME>HH>MH+HME>DH (254-1414 mean fluorescence intensity). Thus, dehydroxy hispolon was least potent for all three activities. Overall the results indicate that the substitution of a hydroxyl group for a methoxy group at the meta positions of the phenyl rings in curcumin significantly enhanced the anti-inflammatory activity, and the removal of phenyl ring at the 7(th) position of the heptadiene back bone and addition of hydroxyl group significantly increased the anti-proliferative activity of curcumin.

Topics: Anti-Inflammatory Agents; Antineoplastic Agents; Catechols; Cell Line, Tumor; Cell Proliferation; Curcumin; Humans; Reactive Oxygen Species; Structure-Activity Relationship