Ethyl acetate (EtOAc) extract from the stem bark of Erythrina fusca showed a antimalarial activity against the multi-drug-resistant strain (K1) of Plasmodium falciparum, and six flavonoids, lupinifolin (1), citflavanone (2), erythrisenegalone (3), lonchocarpol A (4), liquiritigenin (5), and 8-prenyldaidzein (6), were isolated from the extract. Diprenylated flavanone 4 showed a notable antimalarial activity (IC(50); 1.6 microg/mL); however 1 and 3 did not show the activity, even though these compounds possessed prenylated substitution.

IntroductionMalaria is the major parasitic infection in many tropical and subtropical regions, leading to more than one million deaths (principally among African children) out of 400 million cases each year [1] and to major consequent impacts on economic productivity and livelihood [2]. The incidence of malaria is now increasing because of the appearance of multi-drug resistant Plasmodium falcipalum, therefore new and more effective antimalarial drugs are urgently required.Ochna integerrima Merr. (Ochnaceae) is a tree that is widely distributed in Thailand [3], and the bark of O. integerrima Merr. has been used for digestive disorders as a folk medicine in Thailand [4]. In phytochemical studies on O. integerrima Merr, many flavonoids have been isolated [5], [6], [7]. During a screening for antimalarial active sources among Thai plants, it was found that the 80 % EtOH extract from the outer bark of O. integerrima Merr.showed significant anti-malarial activity. The active ingredients in the outer bark were clarified in the present study. Materials and Methods ApparatusOptical rotations were measured on a JASCO polarimeter. 1 H-and 13 C-NMR spectra were determined on a Varian Mercury-300. Mass spectra (MS) were obtained on JEOL MXA-AM505HA and JMS-700 MStation spectrometers. Chromatographic separations were carried out by column chromatography on Wakogel C-200 (75 ± 150 mm, Wako; Osaka, Japan). Preparative reverse phase HPLC was carried out on PEGASIL (250 20 mm i. d., Senshu Co. Ltd.; Tokyo, Japan). Antimalarial Activity of Biflavonoids from Ochna integerrimaChikara AbstractDuring the screening of antimalarial substances, the 80 % EtOH extract from the outer bark of Ochna integerrima Merr. (Ochnaceae) was shown to have a good anti-malarial activity (IC 50 value: 6.5 mg/mL) whereas extracts from the inner barks of O. integerrima showed no antimalarial activity. Biflavanone (1), which had not been found previously from a natural plant source, was isolated as a potent antimalarial active ingredient (IC 50 value: 80 ng/mL) from the extract of the outer barks. The stereoisomer of 1 ( = compound 2) was also isolated from this plant; however, its activity was significantly lower than that of 1. Key wordsAntimalarial´Ochnaceae´Ochna integerrima Merr.´biflavanones Original Paper 611This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited. Analytical methodsAnalytical HPLC experiments were performed on an Agilent 1100 series HPLC instrument (Agilent Technologies Japan, Ltd.; Tokyo, Japan) equipped with a column of PEGASIL (250 4.6 mm i. d., Senshu Co. Ltd.; Tokyo, Japan). The solvent system used was a linear gradient of acetonitrile from 30 % to 60 % during 30 minutes in 10 mM phosphoric acid. Flow rate was 1 mL/min. Injection volume was 10 mL for MeOH solution of all the samples. Concentrations of the samples were 10 mg/mL for extracts and 1 mg/ mL for the isolated compounds. Plant material Extraction and isolationThe outer barks of O. integerrima (485 g) were extracted with 80...

Vitamin K (VK) has a protective effect on neural cells. Methylmercury is a neurotoxicant that directly induces neuronal death in vivo and in vitro. Therefore, in the present study, we hypothesized that VK inhibits the neurotoxicity of methylmercury. To prove our hypothesis in vitro, we investigated the protective effects of VKs (phylloquinone, vitamin K(1); menaquinone-4, vitamin K(2) ) on methylmercury-induced death in primary cultured neurons from the cerebella of rat pups. As expected, VKs inhibited the death of the primary cultured neurons. It has been reported that the mechanisms underlying methylmercury toxicity involve a decrement of intracellular glutathione (GSH). Actually, treatment with GSH and a GSH inducer, N-acetyl cysteine, inhibited methylmercury-induced neuronal death in the present study. Thus, we investigated whether VKs also have protective effects against GSH-depletion-induced cell death by employing two GSH reducers, L-buthionine sulfoximine (BSO) and diethyl maleate (DEM), in primary cultured neurons and human neuroblastoma IMR-32 cells. Treatment with VKs affected BSO- and DEM-induced cell death in both cultures. On the other hand, the intracellular GSH assay showed that VK(2), menaquinone-4, did not restore the reduced GSH amount induced by methylmercury or BSO treatments. These results indicate that VKs have the potential to protect neurons against the cytotoxicity of methylmercury and agents that deplete GSH, without increasing intracellular GSH levels. The protective effect of VKs may lead to the development of treatments for neural diseases involving GSH depletion.

Antimalarial activities have been identified in four microbial metabolites through a screening programme of existing compounds in the Kitasato Institute chemical library. Hedamycin showed selective and potent activity against both drug-resistant and drug-sensitive strains of Plasmodium falciparum. Simaomicin a exhibited remarkably strong antimalarial activity, although its activity against a drug-resistant strain was weaker than that against a drugsensitive strain. The antimalarial effects of triacsins C and D are also reported. Keywords antimalarialantibiotics, hedamycin, simaomicin a , triacsin, Plasmodium falciparum, drugresistant strain As a result of our on-going program of screening soil microorganisms and renewed testing of compounds lodged in the antibiotic library of the Kitasato Institute for Life Sciences, we have previously reported on various microbial metabolites that exhibit potent antimalarial activities [1ϳ5]. We have now discovered four more compounds that possess antimalarial characteristics. Hedamycin, simaomicin a , triacsin C and triacsin D, all from the antibiotic library of the Kitasato Institute, display potent antimalarial activity in vitro. We report here the antimalarial profiles of these four compounds (Fig. 1) [6ϳ8] in comparison with those of clinically-used antimalarial drugs.In vitro activities against Plasmodium falciparum strains K1 (drug-resistant) and FCR3 (drug-sensitive), and cytotoxicity against human diploid embryonic cell line MRC-5 of these compounds, were measured as described previously [1].Hedamycin showed weak activity against both the K1 and FCR3 strain of P. falciparum, similar to the activity of chloroquine for K1 strain (Table 1). The IC 50 value of chloroquine to the K1 strain is 10-fold higher than to the FCR3 strain, indicating that the antimalarial action of hedamycin is different from that of chloroquine. Although the compound does not meet the UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR) criteria for whole cell screening (IC 50 Ͻ0.1 mg/ml for P. falcipurum K1 strain), it could be a promising lead if the activity could be improved since it has low cytotoxicity (IC 50 Ͼ25 mg/ml).Simaomicin a showed the most potent activity against both drug-resistant K1 and drug-sensitive FCR3. The IC 50 values of the compound were remarkably lower than those of the clinically-used antimalarial drugs, artemether, artemisinin and chloroquine. The cytotoxicity of the compound was weaker (IC 50 ϭ4 ng/ml) than its antimalarial activities. Simaomicin a was 4.6-fold less active against the K1 strain than the FCR3 strain. Although simaomicin a showed considerably more potent antimalarial activity than that of the other compounds, the presence of a polycyclic xanthone structure containing an isoquinoline moiety may

To discover antimalarial substances from plants cultivated in Thailand 80%-EtOH extracts from selected plants were screened for in vitro antimalarial activity against the drug resistant K1 strain of Plasmodium falciparum. In total, 86 Thai medicinal plant samples representing 48 species from 35 genera in 16 families were screened and two species (Polyalthia viridis and Goniothalamus marcanii) were found to show notable antimalarial activity (IC50: 10.0 and 6.3 microg/mL). Marcanine A and 16-hydroxycleroda-3,13(14)Z-dien-15,16-olide were identified as the respective major active constituents in P. viridis and G. marcanii, respectively.

K. RATA, JPMW Coordination Center, for valuable discussion. We also thank Mr. Y. KATO and Ms. M. SUZUKI, the Kitasato Institute, for the antimalarial assay, Dr.

No abstract

Brain-derived neurotrophic factor (BDNF) is a principal factor for neurogenesis, neurodevelopment and neural survival through a BDNF receptor, tropomyosin-related kinase (Trk) B, while BDNF can also cause a decrease in the intracellular glutathione (GSH) level. We investigated the exacerbation of methylmercury-induced death of rat cerebellar granular neurons (CGNs) by BDNF in vitro. Since methylmercury can decrease intracellular GSH levels, we hypothesized that a further decrease of the intracellular GSH level is involved in the process of the exacerbation of neuronal cell death. In the present study, we established that in CGN culture, a decrease of the intracellular GSH level was further potentiated with BDNF in the process of the methylmercury-induced neuronal death and also in GSH reducer-induced neuronal death. BDNF treatment promoted the decrease in GSH levels induced by methylmercury and also by L-buthionine sulfoximine (BSO) and diethyl maleate (DEM). The promoting effect of BDNF was observed in a TrkB-vector transformant of the rat neuroblastoma B35 cell line but not in the mock-vector transformant. These results indicate that the exacerbating effect of BDNF on methylmercury-induced neuronal death in cultures of CGNs includes a further decrease of intracellular GSH levels, for which TrkB is essential.