Darrick S. H. L. Kim

Curcuminoids from Curcuma longa L. (Zingiberaceae) that protect PC12 rat pheochromocytoma and normal human umbilical vein endothelial cells from βA(1–42) insult

beta-Amyloid (betaA) induced oxidative stress is a well-established pathway of neuronal cell death in Alzheimers disease. From turmeric, Curcuma longa L. (Zingiberaceae), three curcuminoids, curcumin, demethoxycurcumin, and bisdemethoxycurcumin, were found to protect PC12 rat pheochromocytoma and normal human umbilical vein endothelial (HUVEC) cells from betaA(1-42) insult, as measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction assay. ED(50) values of curcumin, demethoxycurcumin, and bisdemethoxycurcumin toward PC12 and HUVEC cells were 7.1+/-0.3, 4.7+/-0.1, 3.5+/-0.2 microg/ml and 6.8+/-0.4, 4.2+/-0.3, and 3.0+/-0.3 microg/ml, respectively. These compounds were better antioxidants than alpha-tocopherol as determined by DPPH radical trapping experiment. alpha-Tocopherol did not protect the cells from betaA(1-42) insult even at>50 microg/ml concentration. The results suggest that these compounds may be protecting the cells from betaA(1-42) insult through antioxidant pathway.

Synthesis of betulinic acid derivatives with activity against human melanoma.

Betulinic acid has been modified at C-3, C-20, and C-28 positions and the toxicity of the derivatives has been evaluated against cultured human melanoma (MEL-2) and human epidermoid carcinoma of the mouth (KB) cell lines. This preliminary investigation demonstrates that simple modifications of the parent structure of betulinic acid can produce potentially important derivatives, which may be developed as antitumor drugs.

Preparation of amino acid conjugates of betulinic acid with activity against human melanoma.

Betulinic acid has been coupled with a series of amino acids at C-28 carboxylic acid position and the toxicity of the derivatives has been evaluated against cultured human melanoma (MEL-2) and human epidermoid carcinoma of the mouth (KB) cell lines. A number of amino acid conjugates of betulinic acid showed improved water solubility as well as selective cytotoxicity. This investigation demonstrates that amino acid conjugates of betulinic acid can produce potentially important derivatives, which may be developed as antitumor agents.

Development of C-20 modified betulinic acid derivatives as antitumor agents

Chemical modifications were performed on C-20 position of betulinic acid for a structure-activity relationship study. The evaluation of the compounds using human colon carcinoma HCT-116, human prostate adenocarcinoma PC3, and human melanoma cell lines M14-MEL, SK-MEL-2, and UACC-257 did not show any selective cytotoxicity towards melanoma cells. The results from both MTT reduction assay and SRB staining assay were comparable that no remarkable differences in cytotoxicity profile of the compounds were noticed. The C-20 position was found to be sensitive to the size and the electron density of the substituents in retaining the cytotoxicity of betulinic acid and was found to be undesirable position to derivatize.

Total synthesis of calebin-A, preparation of its analogues, and their neuronal cell protectivity against β-amyloid insult

A total synthesis of Calebin-A (1), a novel curcuminoid isolated from turmeric (Curcuma longa, Zingiberaceae) that has been demonstrated to protect neuronal cells from beta-amyloid insult, was successfully achieved in four steps. Elaborating on this synthetic route, 13 analogues were prepared for a structure-activity relationship (SAR) study. It was found that the parent compound 1 and derivatives 21, 28, and 30 protect PC12 rat pheocromocytoma and IMR-32 human neuroblastoma cells from beta-amyloid(25-35) insult. These results suggest that hydroxy group at para-position is most critical for the expression of biological activity.

Enethiol assisted [3,4] and [3,5] sigmatropic rearrangements during thionation of 2,3-diaroylbicyclo[2.2.1]hepta-5-enes with boron sulfide

Abstract Thionation reaction of 2,3-diaroylbicyclo[2.2.1]hepta-5-enes using in situ generated B 2 S 3 (bis-trialkyltin sulfide or bis-trimethylsilyl sulfide reacted with BCl 3 in toluene) gave [3,4] and [3,5] sigmatropic rearrangement products.