Potentiation by febrifugine of host defense in mice against Plasmodium berghei NK65.

The effect of febrifugine, the main alkaloidal constituent of an antimalarial crude drug, Dichroa febrifuga Lour., on protective immunity in mice infected with erythrocytic stage Plasmodium berghei NK65 was investigated. Febrifugine was administered orally, at a dose of 1 mg/kg/day, to mice before and/or after they were infected intraperitoneally with 2 x 10(6) parasitized red blood cells. Then, mortality and the levels of parasitemia and plasma NO3- [a degradation product of nitric oxide (NO)] were monitored. Febrifugine significantly reduced the mortality and the level of parasitemia. The plasma NO3- concentration began to rise within 2 days after treatment with febrifugine and declined to normal in 2 days when the mice were treated orally with febrifugine once a day for 3 consecutive days before parasite infection. This antimalarial activity of febrifugine was reduced by both N(G)-monomethyl-L-arginine and aminoguanidine. These results indicate that the increased production of NO by febrifugine plays an important role in host defense against malaria infection in mice.

Flavonoids from Cleome droserifolia suppress NO production in activated macrophages in vitro.

The effect of an Egyptian medicinal plant, Cleome droserifolia (Forssk.) Del. on nitric oxide (NO) production in bacillus Calmette-Guérin-induced mouse peritoneal macrophages activated by lipopolysaccharide was investigated in vitro. The methanol extract of C. droserifolia reduced the NO production, and two flavonoids were isolated as the active components. The new one was determined to be 5,4'-dihydroxy-6,7,8,3',5'-pentamethoxyflavone (1) and the other was identified as 5,4'-dihydroxy-6,7,8,3'-tetramethoxyflavone (8-methoxycirsilineol; 2). Compound 1 concentration-dependently suppressed the NO production and was effective at a non-toxic concentration (12.5 micrograms/ml). The suppressive activity of 2 was weaker than that of 1.

(+)-rhododendrol and epi-rhododendrin suppress the NO production by activated macrophages in vivo.

In this study, we investigated the effect of (+)-rhododendrol (1) and epi-rhododendrin (2) isolated from Acer nikoense Maxim. (Aceraceae) on nitric oxide (NO) production in mouse peritoneal macrophages elicited by bacillus Calmette-Guérin and in vitro stimulated by lipopolysaccharide. The NO production was not affected by an oral administration of methanol extract at a dose of 100 mg/kg/day. However, the AcOEt soluble fraction significantly reduced the NO production. (+)-Rhododendrol (1) isolated as an active substance from the AcOEt fraction suppressed the NO production. epi-Rhododendrin (2), the glucoside of (+)-rhododendrol (1) isolated from the n-BuOH fraction, also suppressed the NO production. As NO is one of the critical mediators in inflammation, these results suggest that (+)-rhododendrol (1) and epi-rhododendrin (2) contribute in part to the anti-inflammatory effect of A. nikoense.

Enhancement of NO production in activated macrophages in vivo by an antimalarial crude drug, Dichroa febrifuga.

The effect of an antimalarial crude drug, Dichroafebrifuga Lour. on nitric oxide (NO) production in bacillus Calmette Guérin-induced mouse peritoneal macrophages activated by lipopolysaccharide was investigated. The NO production was significantly enhanced by an oral administration of a MeOH extract of D. febrifuga. Febrifugine (1) was isolated as the main active compound, and the activation was dose-dependent in the dosage range of 0.1-1 mg/kg/day.

[Absolute configuration of the diastereoisomer of 2-amino-3-(1,2-dicarboxyethylthio) propanoic acid from Amanita pantherina].

Four stereoisomers of 2-amino-3-(1,2-dicarboxyethylthio) propanoic acid were prepared by reaction of L- and D-cysteine with fumaric acid. The absolute configuration of the diastereoisomer of 2-amino-3-(1,2-dicarboxyethylthio) propanoic acid from Amanita pantherina were assigned as (2R, 1'R) and (2R, 1'S) by analysis of the optical properties. Pharmacological tests showed that all of the four stereoisomers inhibited the depolarization of NMDA on spinal motorneurones in newborn rats, The inhibition intensity of L-A, D-A and D-B were higher than that of L-B.

A novel class of potent gamma-aminobutyric acid aminotransferase inhibitor, 3-(hydroxyamino)propylamine and analogues.

Hydroxyamino analogues of gamma-aminobutyric acid (GABA) were synthesized and evaluated for inhibitory activity toward gamma-aminobutyric acid aminotransferase (GABA-T). The title compound, 3-(hydroxyamino)propylamine (HPA), showed a potent inhibitory activity. The inhibition is competitive with respect to GABA and the Ki value of GABA-T for HPA is 0.4 mmol. The activity of inhibition is comparable to those of aminoxyacetic acid and valproic acid. 3-(Hydroxyaminomethyl)piperidine (3HMP), a cyclic analogue of HPA, also showed a potent inhibitory activity, whereas 3-(methoxyamino)propylamine (OMe-HPA), 3-(N-hydroxy-N-methylamino)propylamine (NMe-HPA) and 4-(hydroxyamino)piperidine (4HP) showed weak activity.

The culture fluid of Isaira japonica yasuda augments anti-sheep red blood cell antibody response in mice.

Isaria japonica YASUDA was cultured in a liquid medium, and its culture fluid (IJCE) was tested for stimulatory activity to humoral antibody production. IJCE significantly enhanced the production of anti-sheep red blood cell (SRBC) plaque forming cells (PFC) by oral ingestions at 10 and 30 mg/kg/d for 4 consecutive days, either before or after SRBC challenge. It also recovered the reduction of anti-SRBC PFC response and number of spleen cells caused by treatment with 5-fluorouracil. It is suggested that IJCE is a promising source for an immunomodulating tool or medicine.

(2R), (1'R) and (2R), (1'S)-2-amino-3-(1,2-dicarboxyethylthio)propanoic acids from Amanita pantherina. Antagonists of N-methyl-D-aspartic acid (NMDA) receptors.

An antagonist of NMDA-sensitive glutamate receptors in rat brain membrane and rat spinal motoneurones was isolated from Amanita pantherina and identified as a diastereoisomeric mixture of 2-amino-3-(1,2-dicarboxyethylthio)propanoic acids. The mixture was separated and the absolute configurations of the components were determined as (2R), (1'R) and (2R), (1'S), by analysis of the optical properties.

Biosynthesis of Phytosiderophores : In Vitro Biosynthesis of 2'-Deoxymugineic Acid from l-Methionine and Nicotianamine.

2' -Deoxymugineic acid (DMA), one of mugineic acid-family phytosiderophores (MAs), was synthesized in vitro both from l-methionine and from nicotianamine (NA) with a cell-free system derived from root tips of iron-deficient barley (Hordeum vulgare L.). The reactions producing DMA from NA needed an amino group acceptor (i.e. 2-oxoglutarate, pyruvate, or oxalacetic acid) and a reductant (i.e. NADH or NADPH). The activity of the enzymes to produce NA from l-methionine was the highest at about pH 9. This biosynthetic activity was markedly induced by iron-deficiency stress. The synthesis of NA from S-adenosyl-l-methionine was more efficient than from l-methionine. From the results with the cell-free system reported here, we propose a revised biosynthetic pathway of MAs.

4-N-hydroxy-L-2,4-diaminobutyric acid. A strong inhibitor of glutamine synthetase.

Analogues of glutamic acid were synthesized and evaluated for their inhibitory activity toward glutamine synthetase (EC 6.3.1.2; GS). The title compound, 4-N-hydroxy-L-2,4-diaminobutyric acid (NH-DABA), showed a potent inhibitory activity against GS from both sheep brain and soybean. The inhibition is competitive with respect to glutamic acid and the Ki values of sheep brain GS and soybean GS for NH-DABA are 0.007 mmol and 0.021 mmol, respectively. The activity of inhibition is comparable to those of L-methionine sulfoximine and 2-amino-4-(hydroxymethyl-phosphinyl)butyric acid (phosphinothricin).