Studies on Plant Growth Substances

The plant growth activities of the dihydro- and tetrahydro-1-naphthoic acids substituted with a halogen, methyl or nitro group at various positions of the aromatic ring are measured by the pea straight-growth test. The relationship between structure and activity is discussed. The results seem to conform well with the spatial structure hypothesis of Veldstra.     

Piscicidal Constituents and Related Diterpene Esters from Aleurites fordii

Piscicidal constituents, A and B, related diterpene esters, C and D, were isolated from the leaves of Aleurites fordii (Euphorbiaceae). A was identified as 12-O-palmitoyl-16-hydroxyphorbol-13-acetate (1). B, C, and D, new diterpene esters, were shown to be 12-O-palmitoyl-4-deoxy-4β-16-hydroxyphorbol-13-acetate (2), 12-O-palmitoyl-4-deoxy-4α-16-hydroxyphorbol-13-acetate (3), and 12-O-palmitoyl-4-deoxy-16-hydroxylumiphorbol-13-acetate (4), respectively.     

The Structure of Gibberellin A23 and the Biological Properties of 3,13-Dihydroxy C20-Gibberellins

Two aldehydic C₂₀-gibberellins, L-2 and L-4, were isolated from the immature fruits of yellow lupine (Lupinus luteus L.). L-2 was shown to have the structure II and named gibberellin A₂₃. L-4 was identified as gibberellin A₁₉(VI). Two new C₂₀-gibberellins, tentatively called 3,13-dihydroxy GA₁₅(IV) and 13-hydroxy GA₁₅(VIII), were derived from gibberellins, A₂₃ and A₁₉, respectively. The biological activities of four 3,13-dihydroxy C₂₀-gibberellins-GA₁₈(I), GA₂₃(II), GA₂₈(III) and 3,13-dihydroxy GA₁₅(IV), which were isolated from the fruits except for 3,13-dihydroxy GA₁₅—were compared in six gibberellin bioassays.     

Desorption Chemical Ionization Mass Spectra of Underivatized Abscisic Acid-conjugated Metabolites,a Useful Aid for Structural Characterization

The use of desorption chemical ionization (D/CI) mass spectrometry for the structural characterization of the abscisic acid (ABA)-conjugated metabolites, abscisic acid-γ-d-glucosyl ester (ABAGE), 4′-O-dihydrophaseic acid-γ-d-glucoside (DPAGS) and γ-hydroxy-γ-methylglutaryl-hydroxyabscisic acid (HMG-HOABA), was studied. The effects of the D/CI source temperature on the spectral features are described. Enhanced quasi-molecular ion intensities (e.g., [M·NH₄]⁺) were observed in the D/CI(NH₃) spectrum at a low source temperature (170°C). When a higher source temperature (250°C) was used, more extensive fragmentation occurred, and structurally diagnostic fragment ions appeared in the spectra. The spectra obtained at two degrees of source temperature were complementary to each other for the structural characterization.     

Structure–activity relationship of C5-curcuminoids and synthesis of their molecular probes thereof

A series of novel analogues of 1,5-bis(4-hydroxy-3-methoxyphenyl)-penta-(1E,4E)-1,4-dien-3-one (C₅-curcumin), which is a natural analogue of curcumin isolated from the rhizomes of Curcuma domestica Val. (Zingiberacea), were synthesized and evaluated for their cytotoxicities against human colon cancer cell line HCT-116 to conclude the SAR of C₅-curcuminoids for further development of their use in cancer chemotherapy: (1) Bis(arylmethylidene)acetone serves as a promising skeleton for eliciting cytotoxicity. (2) The 3-oxo-1,4-pentadiene structure is essential for eliciting cytotoxicity. (3) As for the extent of the aromatic substituents, hexasubstituted compounds exhibit strong activities, in which 3,4,5-hexasubstitution results in the highest potency. (5) The symmetry between two aryl rings is not an essential requirement for bis(arylmethylidene)acetones to elicit cytotoxicity. (6) para-Positions allows the installation of additional functional groups for use as molecular probes. By taking advantage of the SAR diagram, we have elaborated several advanced derivatives having GI₅₀ of single-digit micromolar potencies that will function as molecular probes to target and/or report key biomolecules interacting with curcumin and C₅-curcumin.     

Identification of cDNAs encoding pterocarpan reductase involved in isoflavan phytoalexin biosynthesis in Lotus japonicus by EST mining

Isoflavans and pterocarpans are the major biosynthetically connected phytoalexins in legumes. A search of the expressed sequence tag library of a model legume Lotus japonicus, which produces an (-)-isoflavan, for homologs of phenylcoumaran benzylic ether reductase catalyzing the reductive cleavage of dihydrofurans, yielded seven full-length cDNAs, and the encoded proteins were analyzed in vitro. Four of them cleaved the dihydrofuran of a pterocarpan medicarpin to yield an isoflavan (-)-vestitol and were designated pterocarpan reductase (PTR). Two PTRs displayed enantiospecificity to (-)-medicarpin, representing genuine L. japonicus PTRs, while the other two lacked enantiospecificity and were presumed to be evolutionarily primitive types.     

Free fatty acids administered into the colon promote the secretion of glucagon-like peptide-1 and insulin

We examined whether free fatty acids (FFAs) promote glucagon-like peptide-1 (GLP-1) secretion when administered into the intestinal tract. We found that an unsaturated long-chain FFA, alpha-linolenic acid (alpha-LA), resulted in increased plasma GLP-1 and insulin levels when administered into the colon. Such stimulatory effects were not apparent with either vehicle or a saturated middle-chain FFA, octanoic acid (OA). Concomitant with GLP-1 secretion, the administration of alpha-LA, but not vehicle or OA, also resulted in a significant increase in the population of pERK positive cells within the GLP-1 positive cells of the colonic mucosa. Moreover, colonic administration of alpha-LA into normal C3H/He mice caused a reduction in plasma glucose levels, as well as in type 2 diabetic model NSY mice. Our results indicate that the in vivo colonic administration of alpha-LA promotes secretion of incretin GLP-1 by activating the ERK pathway in L-cells and thereby enhances the secretion of insulin.