Kohei Kamiya

Triterpenoids from callus tissue cultures of Paeonia species

Six triterpenoids were isolated from the callus tissues of Paeonia japonica, P. lactiflora and P. suffruticosa. Four of the compounds are new from a natural source: 11α,12α-epoxy-3β,23-dihydroxyolean-28,13β-olide, 3β-hydroxy-11-oxo-olean-12-en-28-oic acid, 3β-hydroxy-oleana-11,13(18)-dien-28-oic acid and 3β,23-dihydroxy-oleana-11,13(18)-dien-28-oic acid. The postulated biosynthetic sequence of these compounds is discussed and the triterpenoids produced from the three callus tissues have been compared from a chemotaxonomical standpoint.

Triterpenoids and flavonoids from Paeonia lactiflora

Abstract Seven triterpenoids and two flavoids were isolated from the roots and aerial parts of Paeonia lactiflora , respectively. This is the first report of triterpenoids, which is a new triterpene assigned as 11α, 12α-epoxy-3β, 23-dihydroxy-30-norolean-20(29)-en-28,13 β-olide, from this plant.

Chromone C-glycosides from Baeckea frutescens

Abstract Five new chromone C-glycosides have been obtained from the leaves of Baeckea frutescens. They are: 6-β-C-glucopyranosyl-5,7- dihydroxy-2-isopropylchromone, 8-β-C-glucopyranosyl-5,7-dihydroxy-2-isopropylchromone, 6-β-C-glucopyranosyl-5,7-dihydroxy- 2-methylchromone, 6-β-C-(2′-galloylglucopyranosyl)-5,7-dihydroxy-2-isopropylchromone and 8-β-C-(2′-galloylglucopyranosyl)-5,7-dihydroxy-2-isopropylchromone.

β-Sitosterol-3-O-β-D-glucopyranoside : A eukaryotic DNA polymerase λ inhibitor

Beta-sitosterol-3-O-beta-D-glucopyranoside (compound 1), a steroidal glycoside isolated from onion (Allium cepa L.) selectively inhibited the activity of mammalian DNA polymerase lambda (pol lambda) in vitro. The compound did not influence the activities of replicative DNA polymerases such as alpha, delta and epsilon, but also showed no effect even on the activity of pol beta which is thought to have a very similar three-dimensional structure to the pol beta-like region of pol lambda. Since parts of compound 1 such as beta-sitosterol (compound 2) and D-glucose (compound 3) did not influence the activities of any enzymes tested, the converted structure of compounds 2 and 3 might be important for pol lambda inhibition. The inhibitory effect of compound 1 on both intact pol lambda (i.e. residues 1-575) and a truncated pol lambda lacking the N-terminal BRCA1 C-terminus (BRCT) domain (133-575, del-1 pol lambda) was dose-dependent, and 50% inhibition was observed at a concentration of 9.1 and 5.4 microM, respectively. The compound 1-induced inhibition of del-1 pol lambda activity was non-competitive with respect to both the DNA template-primer and the dNTP substrate. On the basis of these results, the pol lambda inhibitory mechanism of compound 1 is discussed.

Inhibition of DNA polymerases and DNA topoisomerase II by triterpenes produced by plant callus

We found that some triterpene compounds could not only selectively inhibit the activities of mammalian DNA polymerase alpha (pol alpha) and beta (pol beta), but could also potently inhibit DNA topoisomerase II (topo II) [Biochem. J. 350 (2000) 757]. Here, we report that natural triterpenes produced by callus from an ancient Chinese medicinal plant were also inhibitors of the enzymes, and some were more selective than others. The natural triterpenes with a carboxyl group equally inhibited the activities of pol alpha, pol beta, and topo II, while the olide-type triterpenes with a ketone group suppressed the activities of pol beta and topo II, but not pol alpha. The other triterpenes from the callus hardly influenced these enzyme activities. As also described previously [J. Biochem. 130 (2001) 657], pol beta and topo II have a three-dimensionally similar triterpene-binding region, which is a pocket in which specific compounds can insert. The newly found triterpene inhibitors might structure-dependently insert into the pocket, and the pocket structure of each enzyme might, three-dimensionally but slightly, differ among them. The triterpene frames could be used for screening new inhibitors of the enzymes, and computer-simulated drug design using the frame and pocket structure may in theory be a possible approach to develop new inhibitors.

New anthraquinone glycosides from the roots of Morinda citrifolia

Six new anthraquinone glycosides: digiferruginol-1-methylether-11-O-beta-gentiobioside (1); digiferruginol-11-O-beta-primeveroside (2); damnacanthol-11-O-beta-primeveroside (3); 1-methoxy-2-primeverosyloxymethyl-anthraquinone-3-olate (4); 1-hydroxy-2-primeverosyloxymethyl-anthraquinone-3-olate (5); and 1-hydroxy-5,6-dimethoxy-2-methyl-7-primeverosyloxyanthraquinone (6) were isolated from Morinda citrifolia (Rubiaceae) roots together with four known anthraquinone glycosides. The structures of the new compounds were established using spectral methods. For five of the new compounds, the sugar is attached via the hydroxymethyl group of the anthraquinone C-2 carbon. This type of bond is rarely found for anthraquinone glycosides isolated from natural sources.

A-type proanthocyanidins from the bark of Parameria laevigata

Parameritannin A-3, a new tetrameric A-type proanthocyanidin, along with the cinnamtannin B-2, pavetannin C-1 and cinnamtannin D-1 have been isolated from the bark of Parameria laevigata. Complete assignments by spectroscopic analysis established their structures as epicatechin - (2β→O→7, 4β→6)-epicatechin - (2β→O→7, 4β→8) - epicatechin - (4β→8) - epicatechin, epicatechin-(4b→8)-epicatechin-(2β→O→7, 4β→8)-epicatechin-(4β→8)-epicatechin, epicatechin-(4β→6)-epicatechin-(2β→O→7, 4β→8)-epicatechin-(4β→8)-epicatechin, epicatechin-(2β→O→7, 4β→8)-epicatechin-(4β→8)-catechin, respectively.

Studies on the constituents of indonesian Borreria latifolia

Seven known iridoid glycosides (1∼7), together with one known diterpenoid (8) were isolated from the aerial parts of Borreria latifolia K. Schum. (Rubiaceae) collected in Indonesia, and their structures were identified byspectroscopic methods.