Pentacyclic triterpenes with selective bioactivity from Sebastiania adenophora leaves, Euphorbiaceae.

Six known pentacyclic triterpenes possessing oleanane, lupane, or taraxerane-type skeletons were isolated from the leaves of Sebastiania adenophora (Euphorbiaceae) and are reported for the first time in this species. These compounds include 3-epi-beta-amyrin, beta-amyrinone, 3-epi-lupeol, lupenone, taraxerol, and taraxerone. Structures were elucidated by comparison with literature data. The bioactivities of these compounds were tested on the root growth of Amaranthus hypochondriacus, amaranth (Amaranthaceae), Lycopersicon esculentum, tomato (Solanaceae), and Echinochloa crus-galli, barnyard grass (Poaceae). All six triterpenes were selectively bioactive. An important stimulatory effect was observed on amaranth root growth (23% to 56%) for almost all tested triterpenes (250 microg/ml). These triterpenes significantly inhibited the root growth of barnyard grass (28% to 78%) and tomato (23% to 49%). Aqueous leachate and organic extracts of S. adenophora leaves significantly inhibited the root growth of all test species. The possible ecological role of the allelochemicals isolated is discussed.

Phytogrowth-inhibitory and antifungal constituents of Helianthella quinquenervis.

Investigation on the roots of Helianthella quinquenervis (Hook.) A. Gray (Asteraceae), led to the isolation of one new benzofuran (6-methoxy-tremetone (1)) and a new prenylacetophenone (4-beta-D-(glucopyranosyloxy)-3-[3-methoxy-trans-isopenten-1 -yl] acetophenone (3)). In addition, 6-hydroxy-3-methoxytremetone (2), encecalin (6), euparin (5), demethylencecalin (4), and angelic acid were obtained. Structural assignments of the isolated compounds were based on spectroscopic and spectrometric analysis. Natural products 1-4 showed marginal cytotoxicity against three human tumor cell lines [MCF-7, A-549, and HT-29]. Compounds 4 and 6 inhibited the radicle growth of Amaranthus hypochondriacus and Echinochloa crusgalli. Furthermore, substances 4-6 exhibited antifungal activity against Trichophyton mentagrophytes.

Phytotoxicity of cacalol and some derivatives obtained from the roots ofPsacalium decompositum (A. Gray) H. Rob. & Brettell (Asteraceae), matarique or maturin.

The effect of cacalol and extracts (water and petroleum ether) derived from the roots ofPsacalium decompositum (Asteraceae) on the germination and radicle growth of two plants.Amaranthus hypochondriacus (Amaranthaceae) andEchinochloa crusgalli (Poaceae), and on the radial growth of four phytopathogenic fungi is described. The activity of two cacalol derivatives (methyl cacalol and cacalol acetate) was also investigated. Germination ofA. hypochondriacus was inhibited by almost all the treatments. The extracts and cacalol produced a significant inhibition of radicle growth ofA. hypochondriacus andE. crusgalli. Cacalol acetate showed a specific inhibition onE. crusgalli, and methyl cacalol significantly inhibited the growth ofA. hypochondriacus. In general, antifungal activity depended upon the target fungi and the concentration of each treatment. Cacalol had also effects on the morphology and coloration of the fungal mycelium. The bioactivity shown by the extracts ofPsacalium decompositum on the tested seeds and fungi is mainly due to their content in cacalol.

Biochemically active sesquiterpene lactones from Ratibida mexicana.

Bioactivity-directed fractionation of the methanol extract of the roots of Ratibida mexicana resulted in the isolation of two bioactive sesquiterpene lactones, isoalloalantolactone and elema-1,3,11-trien-8,12-olide. Both compounds caused a significant inhibition of the radicle growth of Amaranthus hypochondriacus and Echinochloa crus-galli, exerted moderate cytotoxic activity against three different solid tumour cell lines and inhibited significantly the radial growth of three phytopathogenic fungi. Isoalloalantolactone also caused the inhibition of ATP synthesis, proton uptake and electron transport (basal, phosphorylating and uncoupled) from water to methylviologen, therefore acting as a Hill's reaction inhibitor. The lactone did not affect photosystem I but inhibited photosystem II. The site of inhibition of isoalloalantolactone is located in the span of P680 to QA redox enzymes because the uncoupled electron transport from water to silicomolybdate and, from DPC to DCIP are inhibited approximately to the same extent.

Effect of phytotoxic resin glycoside on activity of H(+)-ATPase from plasma membrane.

A resin glycoside mixture isolated fromIpomoea tricolor inhibited radicle growth ofEchinochloa crusgalli. The effect of the resin was tested on the activity of the plasma membrane H(+)-ATPase fromE. crusgalli. For this purpose, plasma membrane vesicles were purified by the method of aqueous two-phase partitioning. The resin glycoside inhibited by 30% the activity of the plasma membrane ATPase. The same result was obtained with the purified main component of the resin. This indicates that the plasma membrane ATPase can be one of the cellular targets of the resin. Hence it is possible that the mechanism of action of the resin involves an inhibition of the plasma membrane ATPase.

Allelopathic potential ofIpomoea tricolor (Convolvulaceae) in a greenhouse experiment.

The allelopathic potential ofIpomoea tricolor, a plant used in Mexican agriculture to control weeds, and tricolorin A, the major phytogrowth inhibitor present in the so-called "resin glycosides" of this plant, have been evaluated by testing leachates of the plant and the compound on the germination and radicle growth ofAmaranthus hypochondriacus, Echinochloa crusgalli, Senna uniflora, I. tricolor, andI. purpurea. The allelopathic potential ofI. tricolor was evaluated in a greenhouse experiment with dryI. tricolor mixed with sterile and nonsterile soil in pots.A. hypochondriacus was sown in pots containingI. tricolor, 2-chloro-4-(ethylamino)-6-(isopropylamino)-1,3,5 triazine (Gesaprim) or 1-glyphosphate, and the glyphosphate salt of isopropylamine (Faena), two different commercial herbicides used as a comparison toI. tricolor. Number and dry weights of different monocotyledonous and dicotyledonous weeds andA. hypochondriacus growing in the different treatments were measured.Ipomoea and Faena herbicide had a similar inhibitory effect on monocots.

5-O-ß-D-galactopyranosyl-7-methoxy-3',4'-dihydroxy-4-phenylcoumarin, an inhibitor of photophosphorylation in spinach chloroplasts.

5-O-ß-D-galactopyranosyl-7-methoxy-3',4'-dihydroxy-4-phenylcoumarin isolated from Exostema caribaeum (Rubiaceae) has been found to act as an energy-transfer inhibitor in spinach chloroplasts. ATP synthesis and phosphorylating (coupled) electron flow were inhibited by 89 and 72%, respectively, at a concentration of 400 µM. H(+)-uptake, basal and uncoupled electron transport were not affected by the coumarin. The light-activated Mg(+2)-ATPase activity from bound membrane thylakoid chloroplasts was slightly inhibited by the coumarin. Also, the heat-activated Ca(+2)-ATPase activity of the isolated coupling factor protein was insensitive to this compound. In chloroplasts partially stripped of coupling factor 1 by an EDTA treatment, the coumarin showed a restoration of the proton uptake process. These results suggest that the 4-phenylcoumarin under investigation inhibited phosphorylation in chloroplasts by specifically blocking the transport of protons through a membrane-bound component or a carrier channel (CFO) located in a hydrophobic region at or near the functional binding site for the coupling factor 1.

Tricolorin A, major phytogrowth inhibitor from Ipomoea tricolor.

The allelopathic potential of Ipomoea tricolor (Convolvulaceae), used in Mexican traditional agriculture as a weed controller, has been demonstrated by measuring the inhibitory activity of organic extracts on seedling growth of Amaranthus leucocarpus and Echinochloa crus-galli. Bioactivity-directed fractionation of the active CHCl3 extract led to the isolation of the allelopathic principle, which turned out to be a mixture of the so-called "resin glycosides" of convolvulaceous plants. The structure of tricolorin A, the major phytogrowth inhibitor present in the active fraction, was elucidated as (11S)-hydroxyhexadecanoic acid 11-O-alpha-L-rhamnopyranosyl-(1-->3)-O-alpha-L-[2-O-(2S-methylbutyryl)-4 -O- (2S-methylbutyryl)] rhamnopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->2)-beta-D-fucopyran oside- (1,3"-lactone)[1], based on chemical methods and spectral analysis including 1H-1H COSY, 1H-13CHETCOR, long range 1H-13C COLOC, and selective INEPT experiments. Bioassays showed that radicle elongation of the two weed seedlings tested was inhibited by tricolorin A [1] with IC50 values ranging from 12 to 37 microM. Staphylococcus aureus was sensitive to compound 1 with an MIC value of 1.8 micrograms/ml. Significant cytotoxic activity against cultured P-388 and human breast cancer cells (ED50 2.2 micrograms/ml) was demonstrated for compound 1, and it also inhibited phorbol 12,13-dibutyrate binding using calf brain homogenate as a source of protein kinase C (IC50 43 microM).

Phenylacetic acid as a phytotoxic compound of corn pollen.

Phenylacetic acid (PAA), one of the phytotoxic compounds in corn (Zea mays) pollen, was identified by GC-MS and by direct comparison with a pure commercial sample of PAA. Bioassays were carried out by testing whole pollen, methylene chloride extract of the pollen, and pure PAA on germination and radical growth ofAmaranthus leucocarpus andEchinochloa crusgalli. The effect of corn pollen was compared with that ofZea mexicana (Teosinte), one of the wild relatives of cultivated maize.

Effects of some compounds isolated fromCelaenodendron mexicanum standl (euphorbiaceae) on seeds and phytopathogenic fungi.

The known compounds friedelin, maytensifolin B, ginkgetin, bilobetin, and amentoflavone as well as the new triterpene 3ß-hydroxyfriedelan-16-one were isolated fromCelaenodendron mexicanum (Euphorbiaceae), an endemic tree of the Pacific Ocean coast of Mexico. The compounds' structures were established on the basis of spectral analysis. The biological effects of aqueous leachates, a CHCl3-MeOH extract and the isolated compounds of leaves and twigs were evaluated on the radicle growth of two plants,Amaranthus leucocarpus andEchinochloa crusgalli, and on the radial growth of three phytopathogenic fungi,Fusarium sp.,Helminthosporium sp., andAlternaria sp. The organic extracts of both leaves and twigs inhibitedAmaranthus and stimulatedEchinochloa radicle growth. On the contrary, friedelin and maytensifolin B stimulatedAmaranthus and inhibitedEchinochloa. The target fungi showed a different response to each treatment, from inhibition to stimulation.

Allelopathic potential of compounds isolated fromIpomoea tricolor cav. (Convolvulaceae).

The allelopathic potential ofI. tricolor, used in traditional agriculture as a weed controller, has been demonstrated by measuring the inhibitory activity of aqueous lixiviates and organic extracts of the plant material on seedling growth ofAmaranthus leucocarpus andEchinochloa crusgalli. Bioactivity-guided fractionation of the most active organic extract led to the isolation of the allelopathic principles, which turned out to be a mixture of glycosides, having jalapinolic acid as the aglycone portion glycosidically linked in the 11 position to an oligosaccharide composed of glucose, rhamnose, and fucose, which also combines with the carboxyl group of the aglycone to form a macrocyclic ester.

Effect of diacetyl piquerol on H(+)-ATPase activity of microsomes fromIpomoea purpurea.

The effect of an allelopathic compound, diacetyl-piquerol on the H(+) -ATPase activity of the microsomal fraction from the radicles of a common weedIpomoea purpurea was studied. The diacetyl-piquerol inhibited the germination and radicle growth fromI. purpurea; the radicle growth was increasingly inhibited (10% to 100%) as piquerol concentrations were raised (10 µM to 1000 µM). The H(+)-ATPase activity was inhibited (48%) by 500 µM diacetyl-piquerol, and this inhibition was higher in plasma membrane ATPase (67.2%) than in tonoplast membrane ATPase (31.4%). Additional studies of the precise physiological mechanisms of interference caused by allelopathic compounds are needed.

Effects of allelopathic compounds of corn pollen on respiration and cell division of watermelon.

The effects of the allelopathic compounds of an "'ethanolic extract" of corn pollen on growth, respiration, and cellular division of watermelon (Citrullus lanatus, var. peacock improved) were studied. Bioassays with the ethanolic extract showed an inhibition of radicle and hypocotyl growth. The effects on respiration were observed in isolated watermelon hypocotyl mitochondria. The ethanolic extract acts as an inhibitor of the electron pathway, decreasing oxygen consumption in state 3, with malate and succinate substrates. The specific inhibition site probably is located before the cytochromec. Ascorbate-TMPD as substrate reversed the inhibitory effect of the ethanolic extract. An evaluation of the mitotic index was made in slide preparations of previously treated meristematic cells. A decrease in mitotic activity of more than 50% was found, as well as irregular and pycnotic nuclei. The data obtained from this study reflect an important mechanism of action of the allelopathic compounds of corn pollen.

Perspectives on allelopathy in mexican traditional agroecosystems: A case study in tlaxcala.

Agroecosystems in Tlaxcala, Mexico, are surrounded by trees and water channels and have a great variety of cultivated and noncultivated plants. The main results of a study carried out on a traditional agroecosystem in Santa Inés, Tlaxcala are presented. Some ecological aspects of polycultures, plant covers (dry leaves ofAlnus firmifolia, Berula erecta, andJuncus sp.), and the allelopathic potential of crops and noncultivated plants (fresh and dry material) were analyzed. The main plants (trees, shrubs, and herbs) present in the agroecosystem were identified. The total number of weeds in plots where plant covers were added was reduced. The number of nodules ofRhizobium phaseoli and the production of bean and squash increased with plant covers. Corn, beans, and squash showed a clear allelopathic effect, as well asChenopodium murale, Tradescantia crassifolia, Melilotus indicus, andAmaranthus hybridus, among other weeds. The contribution of allelopathy in studies of traditional agroecosystems is of great importance for the management of species in space and time. Allelopathy can be the basis of biological control of pests and weeds and of the discovery of new useful substances.

The influence of sucralfate on ibuprofen absorption in healthy adult males.

Sucralfate (Carafate) is a new anti-ulcer agent the effects of which are mediated locally in the gastrointestinal tract. The use of this compound in conjunction with ulcerogenic drugs such as ibuprofen may represent a means of reducing gastrointestinal irritation. Combined oral therapy, however, requires evaluation of a potential interaction in absorption between those agents. The purpose of this study was to examine the influence of sucralfate coingestion on ibuprofen absorption. Twelve normal, healthy male subjects ingested a single oral 400 mg dose of ibuprofen alone or with sucralfate given as 1 g doses four times a day for 2 days prior to and during the study. Ibuprofen serum concentrations were measured for 12 hours following dosing. Parameters associated with rate of absorption (i.e. Cmax, tmax, Ka) were significantly altered in the presence of sucralfate (p less than 0.05). In contrast, the relative bioavailability of ibuprofen was not significantly different between treatments (p greater than 0.05). Therefore, sucralfate does not alter the extent of ibuprofen absorption and would not be expected to change the response to that anti-inflammatory agent.

Allelopathic potential of corn pollen.

The effects of corn pollen and aqueous leachates of pollen upon the radicle growth ofBidens pilosa, Cassia jalapensis, andRumex crispus are shown. Extractions of pollen with various solvents and methods were carried out so as to assess its active principle and its effect uponC. jalapensis. The preliminary steps to separate and identify the allelopathic compounds of the sonicated and macerated pollen extracted with methylene chloride are described. The strongest inhibitory effect was produced by the hexane fraction. The allelopathic effect of corn pollen upon the growth ofC. jalapensis in several substrates is shown. The possible structure of some of the active fractions is discussed as well as the possibility that the allelopathic potential of pollen might actually occur in nature.

Evaluation of allelopathic potential of dominant herbaceous species in a coffee plantation.

Several shaded coffee plantations in Coatepec, Veracruz (Mexico) are characterized by a dense cover of herbaceous vegetation mainly dominated by species from the Commelinaceae which protect the soil from erosion and presumably contribute to regulating the abundance of other weeds. To detect their alleopathic potential, leachates from fresh, air-dried, or oven-dried plants and litter collected during different months of the year were tested uponBrassica campestris, Bidens pilosa, andRumex sp. seeds. Significant radicle growth inhibitions were obtained mainly from dried plants and litter collected during the rainy season (August). Drainage water collected from pots with fresh, chopped plants and litter produced no inhibitions until the third week of recycling the water. Concentrated soil extracts from chopped plants and litter collected after seven weeks of decomposition produced significant inhibitions on radicle growth ofRumex sp. Dry weight ofBidens pilosa was significantly reduced when grown in soils treated with fresh and chopped plants and litter exposed to natural field conditions for five weeks.

Allelopathic potential ofPiqueria trinervia (Compositae) and piquerols A and B.

Bioassays were carried out to test extracts of roots and leaves ofPiqueria trinervia and solutions of piquerol A and B, in order to appraise their allelopathic potential. Leaves seem to have greater concentrations of inhibitory compounds than roots. Both piquerol compounds show strong biological activity, but piquerol A is the more active.