Bronchodilator activity of Phymatodes scolopendria (Burm.) Ching and its bioactive constituent

Phymatodes scolopendria (Burm.) Ching (Polypodiaceae) is widely used in the Eastern coast of Madagascar to treat respiratory disorders. Bioassay-guided fractionation using guinea pig trachea pre-contracted with histamine to monitor the activity led to the isolation of 1,2-benzopyrone (coumarin) as the main active constituent. Effectively, it induced a concentration-dependent relaxation of the histamine with a median effective concentration (EC(50)) of 35.03 microg/ml, or carbachol (EC(50) = 33.41 microg/ml) pre-contracted guinea pig trachea, and also provoked 100% relaxation at 72.10 microg/ml. It was less active either on KCl pre-contracted trachea (EC(50) = 130.78 microg/ml) or endothelium denuded trachea (153.4 +/- 22 microg/ml). It inhibited, in a non-competitive manner, the histamine and the external calcium spasm effect on the isolated trachea but it did not significantly modify the broncho-constrictive activity of KCl. When combined with theophylline, coumarin produced a significant additive relaxing effect on pre-contracted trachea. Furthermore, its bronchodilator effect was not blocked by propranolol. In vivo, pre-treated guinea pig with coumarin showed significant resistance to histamine inhalation, with an adequate dose protecting 50% of the tested animals (AD(50)) of 75 mg/kg. These results indicate that the bronchodilator effect of coumarin is partly due to the endothelium-dependent tracheal relaxation, and may be mediated through a non-specific tracheal relaxation.

Voacamine, a bisindolic alkaloid from Peschiera fuchsiaefolia, enhances the cytotoxic effect of doxorubicin on multidrug-resistant tumor cells

Multidrug-resistance (MDR) is largely caused by the efflux of therapeutics from the tumor cell by means of P-glycoprotein (P-gp), resulting in reduced efficacy of the chemotherapy. In order to overcome MDR, substances, such as verapamil and cyclosporin A (CsA), were employed. As these P-gp modulating agents did not seem promising in clinical practice, new compounds with a low degree of undesirable side effects, were introduced. In this study, bisindolic alkaloid voacamine was examined for its possible capability of enhancing the cytotoxic effect of doxorubicin (DOX) on drug resistant cells. Two different pairs of tumor cell lines were analyzed: the parental lymphoblastoid cell line CEM-WT and its MDR derivative CEM-R, the parental osteosarcoma cell line U-2 OS-WT and its resistant counterpart U-2 OS-R. These cell lines were characterized for their morphological features by scanning electron microscopy (SEM) and for the expression of the main drug transporters by flow cytometric analysis. The effects of voacamine on the cell survival and on both accumulation and efflux of DOX were then investigated. The intracellular distribution of DOX, given alone or in association with CsA or voacamine, was observed by laser scanning confocal microscopy. A differential effect of voacamine between sensitive and resistant cells on the intracellular DOX concentration and distribution was shown. In particular, voacamine induced a significant increase of drug retention and intranuclear location in resistant cells. The results of cell survival experiments revealed an enhancement of the cytotoxic effect of DOX induced by voacamine, confirmed by evident morphological changes observed by SEM. These findings suggest promising applications of this natural substance against MDR tumors.

Studies on vasoconstrictor activity of Curculigo pilosa extracts and of its isolated compounds

The Curculigo pilosa total extract, its butanolic fraction (0.5 microg-100 mg/kg) and the most active in vitro compound structurally similar to adrenaline, pilosidine (10 ng-l mg/kg), caused a reversible and dose-dependent increase in blood pressure in anaesthetized rat. This hypertensive effect is partially reversed (90%) by the prior administration of phentolamine (1 mg/kg) and abolished by pre-treatment with phentolamine (1 mg/kg) and atenolol (100 microg/kg). Neither tachiphylaxis nor any toxic effects were observed. These experimental findings suggest an interaction between C. pilosa and the peripheral adrenergic system (particularly with alpha1 and beta1 receptors); the structure of the bioactive glucosides could be important in evoking this effect.

The co-occurrence of C(3) epimer Nb,C(21)-secocuran alkaloids in Strychnos diplotricha and Strychnos myrtoides

From the stem bark of Strychnos diplotricha, three Nb,C(21)-secocuran alkaloids, viz., 3-epi-myrtoidine, 11-demethoxy-3-epi-myrtoidine and 11-demethoxy-12-hydroxy-3-epi-myrtoidine, were isolated together with the known myrtoidine and 11-demethoxymyrtoidine. They also occur in different parts of S. myrtoides.

Biological activities of the plant-derived bisindole voacamine with reference to malaria

The in vivo antiplasmodial activity of voacamine was assessed in a 4-day test. It was shown to exhibit in vivo activity with 25.4% and 43.4% inhibition of parasitaemia with 2.5 and 10 mg/kg, respectively. In synchronized cultures, it was found to act on trophozoite and schizont stages of Plasmodium falciparum. Using the FMC29 strain of Plasmodium falciparum as parasite and the isobologram curve as a method to assess interaction in drug combination, it was shown to lack any chloroquine-enhancing activity and its in vitro antiplasmodial effect was not potentiated by the chemosensitizer malagashanine.

Benzylbenzoate and norlignan glucosides from Curculigo pilosa: structural analysis and in vitro vascular activity

From the rhizomes of Curculigo pilosa, two benzylbenzoate diglucosides, piloside A and piloside B, and a glucosyl-fused norlignan, pilosidine, previously obtained only as the tetra-O-methyl derivative, were isolated. Pilosidine showed facilitating effect on adrenaline evoked contractions in rabbit aorta isolated preparations.

Antiplasmodial activity of the alkaloids of Peschiera fuchsiaefolia

The tertiary and quaternary alkaloids isolated from the stem bark, root bark and seeds of Peschiera fuchsiaefolia are reported. The tertiary alkaloid crude extract from the stem bark was tested in vitro against Plasmodium falciparum on the basis of the antimalarial use of the plant. It showed good activity against both the D6 strain (IC50 = 495 ng/ml) and chloroquine-resistant W2 strain (IC50 = 817 ng/ml) and voacamine was the most active of the tested alkaloids (IC50 = 238 ng/ml for D6 and 290 ng/ml for W2). The tertiary alkaloid crude extract from the root bark of the same plant is more active than voacamine (IC50 = 179 ng/ml for D6 and 282 ng/ml for W2 strain), and is particularly rich in dimeric alkaloids (0.22% of the vegetable material).

Alkaloids of Hernandia voyronii: chloroquine-potentiating activity and structure elucidation of herveline D

Further investigation of Hernandia voyronii led to the isolation of a new pavine-benzyltetrahydroisoquinoline (pavine-BTIQ) dimer, herveline D, together with herveline A, five aporphine alkaloids, two morphinane alkaloids, and their bio-synthetic precursor, i.e., the BTIQ ( S)-reticuline. Hervelines A-D have a moderate intrinsic in vitro antimalarial activity (IC (50) in the range of 1.68-3.28 microM), but displayed different effects ranging from synergism for herveline B and herveline C to simple additive effect for herveline A, and antagonism for herveline D in a chloroquine (CQ) combination evaluation and this was confirmed in vivo for hervelines A and B. Furthermore, the antiplasmoidal activity of CQ was potentiated in vitro by reticuline and its dimethyl derivative laudanosine (for the latter also in vivo), whereas herveline C moderately potentiated in vitro the anti-plasmodial activity of herveline D.

In vitro and in vivo chloroquine-potentiating action of Strychnos myrtoides alkaloids against chloroquine-resistant strains of Plasmodium malaria

Crude alkaloids of Strychnos myrtoides Gilg & Busse, empirically used as an adjuvant to chloroquine (CQ) in Malagasy herbal remedies, were practically devoid of intrinsic in vitro and in vivo antimalarial activity. However, when combined with CQ at a dose level much lower than their IC50 value, they markedly enhanced in vitro the effectiveness of the synthetic drug against a CQ-resistant strain of Plasmodium falciparum. They also enhanced in vivo CQ activity against a resistant strain of Plasmodium yoelii. By counter-current distribution (CCD) separation of the crude alkaloid extract, the two major alkaloids strychnobrasiline (1) and malagashanine (2), together with four minor alkaloids, were isolated. Strychnobrasiline and malagashanine were devoid of both intrinsic antimalarial activity and cytotoxicity effect, but exhibited significant CQ-potentiating actions. These findings could account for the above-mentioned empirical use of S. myrtoides. The present state of research on antimalarial drug from Strychnos genus is also discussed.

[Effect of lipophilic ortho-naphthoquinones on the growth of and production of peroxides by Leptomonas seymouri and Crithidia fasciculata]

The lipophilic o-naphthoquinones CG 8-935, CG 9-442, CG 10-248 and mansonones A, C, E and F inhibit growth of the trypanosomatids Leptomonas seymouri (LS) and Crithidia fasciculata (CF). The most active mansonones were E and F (I50, 0.1-0.4 microM with LS; 0.3-1.2 microM with CF) with cytotoxic activities equal to or higher than quinones CG, as reported previously. Incubation of LS or CF with the CG-quinones and mansonones E and F caused the release of H2O2 and O2-. from the whole cells to the suspending medium, as detected by the microperoxidase and adrenochrome assays, respectively. Lower O2-. and H2O2 production values were obtained with perezone and primine, two p-benzoquinones used as controls. Quinones effect on O2-. and H2O2 production was closely related to their concentration and with mansonones E and F, O2-. production was 4-5-fold higher than H2O2 production. Smaller differences were observed with the CG-quinones. Peroxide production in the assayed organisms was the result of quinone redox-cycling, which involved an anaerobic, reductive phase producing quinols, and an aerobic phase (II), in which quinol oxidation and peroxide production (O2-., H2O2) occurred. With mansonones E and F, and quinone CG, phase II rate was faster than or similar to phase I rate, but with mansonones A and C, the quinols oxidation rate was 8-10-fold slower than the quinones reduction rate. These differences fit in well with a) the quinol oxidation rates, measured in vitro; b) O2-. production by quinols oxidation and c) quinols capability for producing lucigenin chemiluminescence. These results support the assumption that oxyradicals play a relevant role in o-naphthoquinones cytotoxic action, despite the presence of catalase and other protective enzymes in CF and LS. Other effects are not, however, ruled out. CF and LS sensitivity towards the assayed o-quinones was similar or higher than that of Trypanosoma cruzi, thus allowing the use of those organisms for preliminary screening of antichagasic drugs.

Effects of mansonones on lipid peroxidation, P450 monooxygenase activity, and superoxide anion generation by rat liver microsomes

Several structurally related ortho-naphthoquinones isolated from Mansonia altissima Chev (mansonones C, E and F) (a) inhibited NADPH-dependent, iron-catalyzed microsomal lipid peroxidation; (b) prevented NADPH-dependent cytochrome P450 destruction; (c) inhibited NADPH-supported aniline 4-hydroxylase activity; (d) inhibited Fe(III)ADP reduction by NADPH-supplemented microsomes; (e) stimulated superoxide anion generation by NADPH-supplemented microsomes; and (f) stimulated ascorbate oxidation. ESR investigation of ascorbate-reduced mansonone F demonstrated semiquinone formation. Mansonone C had a greater effect than mansonones E and F on NADPH-dependent lipid peroxidation, O2- production and ascorbate oxidation, whereas mansonone E was more effective than mansonones C and F on aniline 4-hydroxylase activity. Mansonones E and F did not inhibit hydroperoxide-dependent lipid peroxidation, cytochrome P450 destruction or microsomal aniline 4-hydroxylase activity. Mansonone C inhibited to a limited degree tert-butyl hydroperoxide-dependent lipid peroxidation, this inhibition being increased by NADPH. Mansonone A, a tetrahydro orthonapthoquinone derivative, was in all respects relatively less effective than mansonones C, E and F. It is postulated that mansonones C, E and F inhibited microsomal lipid peroxidation and cytochrome P450 catalyzed reactions by diverting reducing equivalents from NADPH to dioxygen, but mansonone C (including its reduced form) may also exert direct antioxidant activity.

Two New Glucosides from Hypoxis obtusa: Obtuside A and Obtuside B1,5

From the rhizomes of HYPOXIS OBTUSA two monoglucosides having the same aglycone as hypoxoside, 1-(3',4'- dihydroxyphenyl)-5-(3'',4''-dihydroxyphenyl)-1-pen-ten-4-yne, have been obtained. By methylation followed by hydrogenation they have been transformed into the same compound, 1-(3'-methoxy-4'- O-beta- D-glucopyranosyl-phenyl)-5-(3''-4''-dimethoxyphenyl)-pentane, likewise obtainable through partial hydrolysis of hypoxoside.

Polar Constituents of Calceolaria ascendens1

A new phenylpropanoid glucoside, 1'- O-beta- D-(3,4-dihydroxy-beta-phenyl)-ethyl-4'- O-caffeoyl-beta- D-apiosyl-(1'''-->3')-glucopyranoside, named calceolarioside E, was isolated from CALCEOLARIA ASCENDENS Lind., together with two other phenylpropanoid glucosides, verbascoside and forsythoside A, and cyclohexanols rengyol, isorengyol, and 4-hydroxy-4-(2'-hydroxyethyl)-cyclohexanone.

A New Biflavanone from the Bark of Garcinia kola1

The new I-3', II-3, 3', II-4', I-5, II-5, I-7, II-7-octahydroxy-I-4'-methoxy-I-3, II-8-biflavanone together with known biflavanones GB-1 and GB-2 were isolated from the bark of GARCINIA KOLA.

A new bisbenzylisoquinoline alkaloid from a peruvian curare

From a Peruvian curare a new bisbenzylisoquinoline alkaloid, ( R,S)-nor-N (b)-chondrocurine, 1, was isolated together with the known ( R,R)-curine, 2, (R,S)-chondrocurine, 3, and tubocurarine (as chloride), 5. (13)C-NMR data of 1, 2 and of ( R,S)-di-methylchondrocurine, 4, are reported.

On the alkaloids of Strychnos. XXXV. The occurrence of akagerine in South American Strychnos

Akagerine (3) was isolated from three different species of South American Strychnos: from S. gardneri A. D.C. (Rio de Janeiro, Brazil), together with 11-methoxydiaboline (2); from S. jobertiana Baillon (Brazil), together with diaboline (1): and from S. parvifolia D.C. (Bahia, Brazil).

New trends in the separation of active principles from plants

The extraction and separation of active principles of plant constituents is a difficult task, even for specialized chemists, when many similar substances are found in a single plant. In the case of the presence of alkaloids a separation method based on counter-current distribution with a discontinuous variation of pH can be used for the resolution of very complex mixtures. The alkaloids separated from twenty-seven medicinal plants are reported.

New curare alkaloids. II. New bisbenzylisoquinoline alkaloids from Abuta grisebachii (Menispermaceae)

From Abuta grisebachii Triana & Planchon, Menispermacea used by Sanama tribe for the preparation of curare, five bisbenzylisoquinoline alkaloids have been isolated; four of them are tertiary (peinamine and three new alkaloids, 7-O-demethylpeinamine, N-methyl,7-O-demethylpeinamine and macolidine) and one is a new quaternary alkaloid called macoline. Their structures have been elucidated on the basis of chemical reactions and spectroscopic data.

Peinamine, a new bisbenzylisoquinoline alkaloid from arrow tips (pei-namô) of the Upper Orinoco

A new bisbenzylisoquinoline alkaloid has been isolated from a curare of the Upper Orinoco region. The curare is made by Indians from an unknown plant (probably Menispermacea) and is kept on arrow tips. The structure of the alkaloid, named peinamine, has been elucidated on the basis of its chemical reactions and spectroscopic data (N.M.R., M.S. and O.R.D.).