The anti-cancer efficacy of grape seed extract (GSE) against prostate cancer (PCA) via its anti-proliferative, pro-apoptotic and anti-angiogenic activities in both cell culture and animal models have recently been described by us. GSE is a complex mixture containing gallic acid (GA), catechin (C), epicatechin (EC) and several oligomers (procyanidins) of C and/or EC, some of which are esterified to GA. To determine which components are most active against PCA, an ethyl acetate extract of GSE was separated by reverse-phase high-performance liquid chromatography (HPLC) into three fractions. Fraction 1 was far more effective than others in causing growth inhibition and apoptotic death of human PCA DU145 cells. Of the components in this fraction, GA showed a very strong dose- and time-dependent growth inhibition and apoptotic death of DU145 cells, but C and procyanidins B1 (EC-C dimer), B2 (EC-EC dimer) and B3 (C-C dimer) were nearly ineffective. Mechanistic studies demonstrated a strong caspase-9, caspase-3 and poly (ADP-ribose) polymerase (PARP) cleavages by GA in DU145 cells. Procyanidin oligomers eluting in HPLC Fractions 2 and 3 were obtained in larger quantities by separating GSE into eight fractions (I-VIII) on a gel filtration column. All fractions were analyzed by HPLC-UV and negative-ion electrospray mass spectrometry. Fractions I-III contained the active compound GA and inactive components C, EC, B1 and B2. Fraction IV contained other dimers and a dimer-GA ester and was also less active than GSE in DU145 cells. Fractions V-VIII, however, caused significant growth inhibition and apoptosis with the highest activity present in the later fractions that contained procyanidin trimers and GA esters of dimers and trimers. Together, these observations identify GA as one of the major active constituents in GSE. Several procyanidins, however, and especially the gallate esters of dimers and trimers also may be efficacious against PCA and merit further investigation.

Several studies have documented the anticancer and chemopreventive efficacy of grape seed extract (GSE) against various malignancies including prostate cancer (PCA). GSE is a complex mixture of polyphenols including gallic acid (GA), catechin (Cat), epicatechin (Epi) and procyanidins-oligomers of Cat and Epi, some of which are esterified with GA. Initial studies to identify the GSE components cytotoxic to human prostate carcinoma (DU145) cells demonstrated that GA and several crude chromatographic fractions containing procyanidin dimers and trimers were biologically active. The focus of the present work was to purify 14 procyanidins from the fractions and to identify those with highest activity toward growth inhibition, cell death and apoptosis in DU145 cells. The most active procyanidin was identified by mass spectrometry and enzymatic hydrolysis as the 3,3'-di-O-gallate ester of procyanidin dimer B2 (Epi-Epi). B2-digallate exhibited dose-dependent effects on DU145 cells over the range 25-100 microM, whereas GA exhibited comparable activity at lower doses but was highly lethal at 100 microM. Structure-activity studies demonstrated that all three hydroxyl groups of GA are necessary for activity, but a free carboxylic acid group is not required even though esterification reduced the activity of GA. These data, and the fact that non-esterified B2 exhibited little or no activity, suggest that the galloyl groups of B2-digallate are primarily responsible for its effects on DU145 cells. Taken together, these data identify procyanidin B2-3,3'-di-O-gallate as a novel biologically active agent in GSE that should be studied in greater detail to determine its effects against PCA.

Several bis- and tris-indole derivatives were isolated from a North Sea bacterium that was closely related to Vibrio parahaemolyticus (98% homology). 1,1,3-Tris(3-indolyl)butane (3) is a new compound, and 3,3-bis(3-indolyl)butane-2-one (1a), arundine (1b), and 1,1,1-tris(3-indolyl)methane (2a) were isolated from a microorganism for the first time here. Additionally, many other known compounds were obtained from the ethyl acetate extract of the culture. Their structures were established on the basis of various spectral data, and their origin is discussed. All compounds were inactive against a range of bacteria and fungi.

Two trimeric proanthocyanidins, cinnamtannin B-1 (1) and cinnamtannin D-1 (2), have been isolated from the bark of Cinnamomum cassia along with the known tetramer parameritannin A-1 (3) and a previously unreported tetramer, named cassiatannin A (4). The structures of 1-4 were elucidated on the basis of 1D and 2D NMR, MS, and CD analyses and compared to the reported data. Proanthocyanidins (1-4) possess significant in vitro inhibitory activity against cyclooxygenase-2 (COX-2) at micromolar concentrations.

Furanoid sugar amino acids (1) were synthesized and used as dipeptide isosteres to induce interesting turn structures in small linear peptides. They belong to a new variety of designed hybrid structures that carry both amino and carboxyl groups on rigid furanose sugar rings. Four such molecules, 6-amino-2,5-anhydro-6-deoxy-D-gluconic acid (3, Gaa) and its mannonic (4, Maa), idonic (5, Iaa), and a 3,4-dideoxyidonic (6, ddIaa) congeners were synthesized. The synthesis followed a novel reaction path in which an intramolecular 5-exo S(N)2 opening of the hexose-derived terminal aziridine ring in 2 by the gamma-benzyloxy oxygen with concomitant debenzylation occurred during pyridinium dichromate oxidation of the primary delta-hydroxyl group to carboxyl function, leading to the formation of furanoid sugar amino acid frameworks in a single step. Incorporation of these furanoid sugar amino acids into Leu-enkephalin replacing its Gly-Gly portion gave analogues 8-11. Detailed structural analysis of these molecules by circular dichroism (CD) and various NMR techniques in combination with constrained molecular dynamics (MD) simulations revealed that two of these analogues, 8a and 10a, have folded conformations composed of an unusual nine-membered pseudo beta-turn-like structure with a strong intramolecular H-bond between LeuNH --> sugarC3-OH. This, in turn, brings the two aromatic rings of Tyr and Phe in close proximity, a prerequisite for biological activities of opioid peptides. The analgesic activities of 8a,b determined by mouse hot-plate and tail-clip methods were similar to that of Leu-enkephalin methyl ester. The syn disposition of the beta-hydroxycarboxyl motif on the sugar rings appears to be the driving force to nucleate the observed turn structures in some of these molecules (8 and 10). Repetition of the motif on both sides of a furanose ring resulted in a novel molecular design of sugar diacid, 2,5-anhydro-D-idaric acid (7, Idac). Bidirectional elongation of the diacid moieties of 7 with identical peptide strands led to the formation of a C2-symmetric reverse-turn mimetic 12 which displayed a very ordered structure consisting of identical intramolecular H-bonds at two ends between LeuNH --> sugar-OH, the same as in 8 and 10.