Novel betulin derivatives as multidrug reversal agents targeting P-glycoprotein.

Chemotherapy is a powerful means of cancer treatment but its efficacy is compromised by the emergence of multidrug resistance (MDR), mainly linked to the efflux transporter ABCB1/P-glycoprotein (P-gp). Based on the chemical structure of betulin, identified in our previous work as an effective modulator of the P-gp function, a series of analogs were designed, synthesized and evaluated as a source of novel inhibitors. Compounds 6g and 6i inhibited rhodamine 123 efflux in the P-gp overexpressed leukemia cells, K562/Dox, at concentrations of 0.19 µM and 0.39 µM, respectively, and increased the intracellular accumulation of doxorubicin at the submicromolar concentration of 0.098 µM. Compounds 6g and 6i were able to restore the sensitivity of K562/Dox to Dox at 0.024 µM and 0.19 µM, respectively. Structure-activity relationship analysis and molecular modeling revealed important information about the structural features conferring activity. All the active compounds fitted in a specific region involving mainly transmembrane helices (TMH) 4-6 from one homologous half and TMH 7 and 12 from the other, also showing close contacts with TMH 6 and 12. Compounds that bound preferentially to another region were inactive, regardless of their free energy of binding. It should be noted that compounds 6g and 6i were devoid of toxic effects against peripheral blood mononuclear normal cells and erythrocytes. The data obtained indicates that both compounds might be proposed as scaffolds for obtaining promising P-gp inhibitors for overcoming MDR.

The thiophene α-terthienylmethanol isolated from Tagetes minuta inhibits angiogenesis by targeting protein kinase C isozymes α and ß2.

Background: Tumor angiogenesis is considered as a crucial pathologic feature of cancer with a key role in multidrug resistance (MDR). Adverse effects of the currently available drugs and the development of resistance to these remain as the hardest obstacles to defeat. Objetive: This work explores flora from Argentina as a source of new chemical entities with antiangiogenic activity. Methods: Tube formation assay using bovine aortic endothelial cells (BAECs) was the experiment of choice to assess antiangiogenic activity. The effect of the pure compound in cell invasiveness was investigated through the trans-well migration assay. The inhibitory effect of the pure compound on VEGFR-2 and PKC isozymes α and ß2 activation was studied by molecular and massive dynamic simulations. Cytotoxicity on peripheral blood mononuclear cells and erythrocyte cells was evaluated by means of MTT and hemolysis assay, respectively. In silico prediction of pharmacological properties (ADME) and evaluation of drug-likeness features were performed using the SwissADME online tool. Results: Among the plants screened, T. minuta, showed an outstanding effect with an IC50 of 33.6 ± 3.4 µg/ml. Bio-guided isolation yielded the terthiophene α-terthienylmethanol as its active metabolite. This compound inhibited VEGF-induced tube formation with an IC50 of 2.7 ± 0.4 µM and significantly impaired the invasiveness of bovine aortic endothelial cells (BAECs) as well as of the highly aggressive breast cancer cells, MDA-MB-231, when tested at 10 µM. Direct VEGFR-2 and PKC inhibition were both explored by means of massive molecular dynamics simulations. The results obtained validated the inhibitory effect on protein kinase C (PKC) isozymes α and ß2 as the main mechanism underlying its antiangiogenic activity. α-terthienylmethanol showed no evidence of toxicity against peripheral blood mononuclear and erythrocyte cells. Conclusion: These findings support this thiophene as a promising antiangiogenic phytochemical to fight against several types of cancer mainly those with MDR phenotype.

Plant extracts and betulin from Ligaria cuneifolia inhibit P-glycoprotein function in leukemia cells.

Overexpression of P-glycoprotein (P-gp), which is linked to multidrug resistance (MDR), is one of the underlying obstacles to the success of chemotherapy as it reduces the efficacy of anticancer drugs and the side effects of these increase as a result of any increased dose to achieve the therapeutic effect. To identify agents with P-gp inhibitory properties, ethanol extracts from 80 plants were screened for their ability to increase intracellular doxorubicin-associated fluorescence, and the extract of Ligaria cuneifolia was found to be the most effective. Its bioassay-guided isolation yielded the pentacyclic triterpene betulin as active agent. This efficiently inhibited P-gp mediated efflux, as demonstrated by the enhancement of the intracellular accumulation of doxorubicin and rhodamine 123 from 1.56 µM in the P-gp overexpressing MDR leukemia cell, Lucena 1. Betulin was also able to render Lucena 1 sensitive to Dox from 0.39 µM. The docking studies revealed that betulin tightly binds to a key region of the TMDs, with a binding mode overlapping one main site of doxorubicin and, more interestingly, emulating the same contacts as tariquidar, as revealed by the per-residue energetic analysis from molecular dynamics simulations. MTT assay using peripheral blood mononuclear cells and hemolysis assay showed that betulin is devoid of toxicity. These findings provide important evidence that betulin may be a safe and promising entity to be further investigated to develop agents able to overcome P-gp-mediated MDR, resulting in a more effective and less toxic chemotherapy.

Cytotoxic Activity of Germacrane-Type Sesquiterpene Lactones from Dimerostemma aspilioides.

The need for effective candidates as cytotoxic drugs that at the same time challenge cancer multidrug resistance encouraged a search for these in plants of central Argentina. Bioassay-guided fractionation of the cytotoxic extract from Dimerostemma aspilioides led to the isolation of the germacranolide tomenphantin A (1), along with three new analogues (2-4). These efficiently inhibited the proliferation of the leukemia cell lines K562 and CCRF-CEM and their resistant variants, Lucena 1 and CEM/ADR5000, respectively, with IC50 values ranging from 0.40 to 7.7 µM. The structures and relative configurations of compounds 1-4 were elucidated by analysis of the spectroscopic data, in particular NMR spectroscopy. The most active among these was compound 1 (IC50 = 0.40-5.1 µM), and, therefore, this was selected as a model for a mechanistic study, which revealed that its antiproliferative effect was mediated by cell cycle arrest in the G2/M phase followed by apoptosis. The activity of compound 1 was selective, given the absence of cytotoxicity toward peripheral blood mononuclear cells. The results show the potential of these compounds, and in particular of compound 1, as leads for the development of drug candidates to fight sensitive and resistant leukemia cells.

Antifeedant effect of polygodial and drimenol derivatives against Spodoptera frugiperda and Epilachna paenulata and quantitative structure-activity analysis.

BACKGROUND: The antifeedant activity of 18 sesquiterpenoids of the drimane family (polygodial, drimenol and derivatives) was investigated. RESULTS: Polygodial, drimanic and nordrimanic derivatives were found to exert antifeedant effects against two insect species, Spodoptera frugiperda and Epilachna paenulata, which are pests of agronomic interest, indicating that they have potential as biopesticide agents. Among the 18 compounds tested, the epoxynordrimane compound (11) and isonordrimenone (4) showed the highest activity [50% effective concentration (EC50 ) = 23.28 and 25.63 nmol cm-2 , respectively, against S. frugiperda, and 50.50 and 59.00 nmol/cm2 , respectively, against E. paenulata]. CONCLUSION: The results suggest that drimanic compounds have potential as new agents against S. frugiperda and E. paenulata. A quantitative structure-activity relationship (QSAR) analysis of the whole series, supported by electronic studies, suggested that drimanic compounds have structural features necessary for increasing antifeedant activity, namely a C-9 carbonyl group and an epoxide at C-8 and C-9. © 2018 Society of Chemical Industry.

Analogues of the Lignan Pinoresinol as Novel Lead Compounds for P-glycoprotein (P-gp) Inhibitors.

To find novel P-gp-inhibitors, a library of pregnane X receptor (PXR) ligands and the ZINC DrugsNow library were superimposed on the P-gp inhibitor (+)-pinoresinol (1) used as a query for a three-dimensional similarity search. After determining the TanimotoCombo index of similarity with 1, eight compounds from the PXR library and two ZINC compounds were selected for biological evaluation. The P-gp inhibition study showed that compounds 7, 8, and 9 successfully increased intracellular doxorubicin (DOX) accumulation in the P-gp overexpressed Lucena 1 cells from 25, 12.5, and 6.25 µM, respectively. Among a series of analogues of 9, compounds 26-30 were shown to be active, with 26 and 27 causing a significant increase in DOX accumulation from 1.56 µM and rendering Lucena 1 sensitive to DOX from 1.56 and 0.78 µM, respectively. Molecular modeling studies showed that both compounds bind to the P-gp at transmembrane helices (TMH) 4, 5, and 6, with 27 also showing contacts with TMH 3.

Mechanism Underlying the Reversal of Drug Resistance in P-Glycoprotein-Expressing Leukemia Cells by Pinoresinol and the Study of a Derivative.

P-glycoprotein (P-gp) is a membrane protein associated with multidrug resistance (MDR) due to its key role in mediating the traffic of chemotherapeutic drugs outside cancer cells, leading to a cellular response that hinders efforts toward successful therapy. With the aim of finding agents that circumvent the MDR phenotype mediated by P-gp, 15 compounds isolated from native and naturalized plants of Argentina were screened. Among these, the non-cytotoxic lignan (±) pinoresinol successfully restored sensitivity to doxorubicin from 7 µM in the P-gp overexpressed human myelogenous leukemia cells, Lucena 1. This resistance-reversing effect was confirmed by competitively increasing the intracellular doxorubicin accumulation and by significantly inhibiting the efflux of doxorubicin and, to a lesser extent, that of rhodamine 123. The activity obtained was similar to that observed with verapamil. No such results were observed in the sensitive parental K562 cell line. To gain deeper insight into the mode of action of pinoresinol, its effect on P-gp function and expression was examined. The docking simulations indicated that the lignan bound to P-gp at the apex of the V-shaped transmembrane cavity, involving transmembrane helices 4, 5, and 6, and partially overlapped the binding region of tariquidar, which was used as a positive control. These results would shed some light on the nature of its interaction with P-gp at molecular level and merit further mechanistic and kinetic studies. In addition, it showed a maximum 29% activation of ATP hydrolysis and antagonized verapamil-stimulated ATPase activity with an IC50 of 20.9 µM. On the other hand, pinoresinol decreased the presence of P-gp in the cell surface. Derivatives of pinoresinol with improved activity were identified by docking studies. The most promising one, the non-cytotoxic 1-acetoxypinoresinol, caused a reversion of doxorubicin resistance from 0.11 µM and thus higher activity than the lead compound. It also caused a significant increase in doxorubicin accumulation. Results were similar to those observed with verapamil. The results obtained positioned these compounds as potential candidates for effective agents to overcome P-gp-mediated MDR, leading to better outcomes for leukemia chemotherapy.

Phytotoxic phenylpropanoids isolated from Ophryosporus charua (Griseb.) Hieron.

Bioguided isolation of the EtOH extract from the medicinal native plant, Ophryosporus charua, against Raphanus sativus, yielded three phenylpropanoids, charuol A [(Z)-4-((1S,2R)-3-acetoxy-1,2-dihydroxypropyl)phenyl) 2-methylbut-2-enoate], charuepoxide [(Z)-4-((2S,3R)-3-(acetoxymethyl oxiran-2-yl)phenyl) 2-methylbut-2-enoate] and charuol B [(Z)-4-((1R,2R)-3-acetoxy-1,2-dihydroxypropyl)phenyl) 2-methylbut-2-enoate]. Their structures and absolute configuration were established by extensive spectroscopic analyses. The effective concentrations for 50% inhibition of germination (ECg50) and root (ECr50) and shoot (ECs50) elongations were determined for these compounds against P. miliaceum (monocot) and Raphanus sativus (dicot). Charuol A was the most active in the inhibition of germination of P. miliaceum (ECg50 = 0.97 mM), followed by charuol B and charuepoxide, although charuol B was the most effective in regulating the root growth of P. miliaceum seedlings, with an ECr50 of 1.0 mM. Charuol A inhibited the germination of R. sativus, while its seedling development was also affected by all three compounds with different effectiveness. Charuol A was also highly effective in the 0.09-0.30 mM range against other test species such as Lactuca sativa, Eruca sativa, Allium ampeloprasum and Secale cereale.

Insecticidal Properties of a Highly Potent Wax Isolated from Dolichandra cynanchoides Cham.

Bioassay-guided fractionation of an ethanolic extract of the aerial parts of Dolichandra cynanchoides Cham. (Bignoniaceae) led to the isolation of a natural wax with anti-insect activity against Spodoptera frugiperda (Noctuidae) and Epilachna paenulata (Coleptera). The compound was identified spectroscopically as an ester of a C27 fatty acid and a C25 alcohol, pentacosyl heptacosanoate (1). The effective doses of 1 for 50% feeding inhibition (ED50) of S. frugiperda and E. paenulata were 0.82 and 8.53 µg/cm², respectively, in a choice test, while azadirachtin showed ED50 of 0.10 and 0.59 µg/cm², respectively. In a no-choice test, both insects refused to feed on leaves treated with 1 at doses of 0.1 µg/cm² or greater inhibiting larval growth and dramatically reducing survival. The lethal doses 50 (LD50) of 1 were 0.39 and 0.68 µg/cm² for S. frugiperda and E. paenulata, respectively. These results indicate that 1 has potential for development as botanical insecticides. Similar esters might be obtainable in large quantities as many edible crops produce wax esters that are discarded during food processing. Research on these materials could lead to the detection of similar waxes with insecticidal activity.

Screening for extracts with insect antifeedant properties in native plants from central Argentina / Evaluación de la actividad antialimentaria de insectos en extractos de plantas nativas del centro de Argentina

Ethanol extracts obtained from aerial parts of 64 native plants from Central Argentina were tested for their insect antifeedant activity against Epilachna paenulata (Coleoptera: Coccinellidae) by choice test. Extracts derived from Achyrocline satureioides (Asteraceae), Baccharis coridifolia (Asteraceae), Baccharis flabellata (Asteraceae), Ruprechtia apetala (Polygonaceae) and Vernonanthura nudiflora (Asteraceae), showed more than 97 percent inhibition of the feeding of E. paenulata at 100 micrograms/cm2. These active extracts were further evaluated for their effectiveness against Spodoptera frugiperda (Lepidoptera: Noctuidae). All these extracts except for that derived from A. satureioides, negatively influenced the feeding behavior of S. frugiperda at 100 microrams/cm2...

Se evaluaron los extractos etanólicos obtenidos de las partes aéreas de 64 plantas de la región Central de Argentina, como antialimentarios de insectos mediante ensayos de elección, contra Epilachna paenulata (Coleoptera: Coccinellidae). Los extractos derivados de Achyrocline satureioides (Asteraceae), Baccharis coridifolia (Asteraceae), Baccharis flabellata (Asteraceae), Ruprechtia apetala (Polygonaceae) y Vernonanthura nudiflora (Asteraceae) mostraron mas de 97 por ciento de inhibición de la alimentación de E. paenulata a 100 microgramos/cm2. Estos extractos fueron posteriormente evaluados en su efectividad contra Spodoptera frugiperda (Lepidoptera: Noctuidae). Todos ellos, con excepción del extracto de A. satureioides, afectaron negativamente el comportamiento alimentario de S. frugiperda a 100 microgramos/cm2...

Antibacterial activity of the plant-derived compounds 23-methyl-6-O-desmethylauricepyrone and (Z,Z)-5-(trideca-4,7-dienyl)resorcinol and their synergy with antibiotics against methicillin-susceptible and -resistant Staphylococcus aureus.

The present study investigated the antibacterial activity of two plant-derived compounds, 23-methyl-6-O-desmethylauricepyrone (1) and (Z,Z)-5-(trideca-4,7-dienyl)resorcinol (2), and their synergistic effects with erythromycin and gentamicin against methicillin-susceptible (MSSA) and gentamicin- and methicillin-resistant Staphylococcus aureus (MRSA). Studies of the individual antibacterial activity of each plant-derived compound and synergy experiments were carried out, by the microdilution test in agar and by the checkerboard method, respectively. Compound 1 showed minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 2 and 8 µg/mL, respectively, against both strains of S. aureus, while compound 2 exhibited anti-MSSA and anti-MRSA activity with MICs and MBCs of 4 and 8 and 2 and 8 µg/mL, respectively. Time-kill curves showed that, while compound 1 produced complete killing of both strains at 24 h from the beginning of the experiment, 2 produced the same effect in the first hour. Combinations of 1 with erythromycin or gentamicin showed a notable synergism against MSSA, which enabled the antibiotic concentration to decrease by up to 300 or 260 times, respectively. When the aminoglycoside was placed together with compound 2, only an additive effect was observed. The assayed compounds did not produce erythrocyte hemolysis or genotoxicity and they did not affect macrophage viability at the effective or higher concentrations. These results suggest that both compounds could be considered as promising antibacterial agents while compound 1 could be used in combinatory therapies with erythromycin and gentamicin.

Antibacterial activity of extracts from plants of central Argentina--isolation of an active principle from Achyrocline satureioides.

The great increase in bacterial infections is fueling interest in the search for antibacterial products of plant origin. Extracts obtained from 51 native and naturalized plants from central Argentina were therefore evaluated for their IN VITRO inhibitory activity on pathogenic bacteria with the aim of selecting the most active ones as new sources of effective antibiotics. The susceptibility of reference and clinical strains of Enterococcus faecalis, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella enterica serovar Enteritidis, and Staphylococcus aureus was determined. Extracts from Achyrocline satureioides, Flourensia oolepis, Lepechinia floribunda, and Lithrea molleoides were the most potent, with MIC and MBC values ranging from 0.006 to 2 and 0.012 to 10 mg/mL, respectively, on both gram-positive and negative bacteria. The antibacterial activity-guided isolation of A. satureioides ethanol extract showed 23-methyl-6-O-desmethylauricepyrone (1) to be the most active compound. This compound showed inhibitory effects against gram-positive bacteria with MIC and MBC values of 0.002 and 0.008 mg/mL, respectively, while on gram-negative strains, the MIC and MBC were 0.062-0.250 and 0.062-0.500 mg/mL, respectively. The strong antibacterial activity shown by the four plant extracts or the compound isolated from A. satureioides suggests that they could become part of the arsenal of antibacterial drugs currently used.

Screening for acetylcholinesterase inhibitory activity in plant extracts from Argentina.

Plants are a potential source of bioactive compounds and offer a promising strategy for the treatment of neurological disorders such as Alzheimer's disease. The inhibitory effect of 73 native and naturalized plants collected from the central region of Argentina on acetylcholinesterase (AChE) was tested using microplate and TLC assays after solvent fractionation of complete ethanol extracts obtained from the plants. Organic fractions obtained from extracts of Achyrocline tomentosa (Asteraceae), Eupatorium viscidum (Asteraceae), Ruprechtia apetala (Polygonaceae) Trichocline reptans (Asteraceae) and Zanthoxylum coco (Rutaceae) presented strong inhibition of AChE (higher than 80%) at 1 mg/mL, with R. apetala and T. reptans being the most potent, showing complete inhibition of the enzyme. Their IC(50) values were 0.0779 and 0.1118 mg/mL, respectively. Aqueous fractions did not show any inhibitory activity on the enzyme. These results suggest that the most effective extracts deserve further investigation with the aim of obtaining new molecules for the treatment of neurodegenerative disorders.

Antifeedant activity of ethanolic extract from Flourensia oolepis and isolation of pinocembrin as its active principle compound.

The ethanolic extract from Flourensia oolepis aerial parts showed strong antifeedant activity against the pest larvae, Epilachna paenulata, with an antifeedant index (AI%) of 99.1% at 100 microg/cm(2). Based on chromatographic fractionation of the extract, guided by bioassays on E. paenulata, the flavanone pinocembrin (1) was isolated as the most active principle. In a choice assay, compound 1 showed strong antifeedant activity against E. paenulata, Xanthogaleruca luteola and Spodoptera frugiperda with an AI% of 90, 94 and 91% (p<0.01) respectively, at 50 microg/cm(2). The dosages necessary for 50% feeding inhibition of the insects (ED(50)) were 7.98, 6.13 and 8.86 microg/cm(2), respectively. The feeding inhibitory activity of 1 against E. paenulata was compared with the activity of other structurally related flavonoids like naringenin, which was inactive up to 100 microg/cm(2), catechin which was nearly 6 times less active than 1, and quercetin which was equally active as 1. The effect of these on the feeding behavior of E. paenulata was also studied.

Screening of Argentinian plants for pesticide activity.

Aerial parts of 27 plant species native to Argentina were tested in anti-insect, germination inhibition and bactericide bio-assays. In antifeedant assays on Epilachna paenulata larvae, 11 species showed strong feeding deterrent effects (higher than 90% at 200 microg/cm(2)). Twelve plants strongly inhibited the germination of Avena sativa seeds, but only six inhibited Raphanus sativum germination at 10 mg/ml. Four plants showed complete growth inhibition of Escherichia coli at a concentration of 2 mg/ml.

In vitro pediculicidal and ovicidal activity of an extract and oil from fruits of Melia azedarach L.

BACKGROUND: Head louse infestation is difficult to control because of increasing lice resistance to synthetic pediculicidal drugs. OBJECTIVE: To test the activity of extract and oil obtained from fruits of Melia azedarach L. against the head louse Pediculus humanus capitis. METHODS: A filter paper diffusion bioassay was carried out in order to determine the pediculicidal and ovicidal activity of extract and oil from M azedarach L. fruits. RESULTS: Both vegetable products, tested either individually or in combinations, showed high levels of mortality on adult lice, with values ranging between 62.9% and 96.5%. The highest mortality rate was obtained with a combination of 20% ripe fruit extract with 10% ripe fruit oil. A formulation made with both extract and oil at 10% plus the addition of emulsifier and preserving agents showed 92.3% pediculicidal activity. The products were also successful in delaying or inhibiting nymph emergence, with the formulation being the most effective, with a complete inhibition of emergence. LIMITATIONS: Because adult lice are sensitive to starvation and therefore control mortalities are often higher than 20% in tests with field specimens, the results may not reflect the direct effect of the extract. CONCLUSIONS: These results demonstrate the possibility of using Melia products for controlling head lice, which are difficult to control because of their resistance to the currently used anti-louse agents.

Laboratory evaluation of Artemisia annua L. extract and artemisinin activity against Epilachna paenulata and Spodoptera eridania.

Ethanolic extract of aerial parts of Artemisia annua L. and artemisinin were evaluated as anti-insect products. In a feeding deterrence assay on Epilachna paenulata Germ (Coleoptera: Coccinellidae) larvae, complete feeding rejection was observed at an extract concentration of 1.5 mg/cm2 on pumpkin leaf tissue. The same concentration produced a feeding inhibition of 87% in Spodoptera eridania (Cramer) (Lepidoptera: Noctuidae). In a no-choice assay, both species ate less and gained less weight when fed on leaves treated with the extract. Complete mortality in E. paenulata and 50% mortality in S. eridania were observed with extract at 1.5 mg/cm2. Artemisinin exhibited a moderate antifeedant effect on E. paenulata and S. eridania at 0.03-0.375 mg/cm2. However, a strong effect on survival and body weight was observed when E. paenulata larvae were forced to feed on leaves treated at 0.03 and 0.075 mg/cm2. Artemisia annua ethanolic extract of aerial parts at 1.5 mg/cm2 showed no phytotoxic effect on pumpkin seedlings.

Antifungal synergistic effect of scopoletin, a hydroxycoumarin isolated from Melia azedarach L. fruits.

In the continuous search for antifungal compounds from plants, the hydroxycoumarin scopoletin (1) was isolated from seed kernels of Melia azedarach L. from which three other compounds, vanillin (2), 4-hydroxy-3-methoxycinnamaldehyde (3), and (+/-) pinoresinol (4), have also been isolated. Guided fractionation through autobiography on TLC using Fusarium verticillioides (Saccardo) Nirenberg as test organism led to the isolation of 1, which exhibited a minimum inhibitory concentration (MIC) of 1.50 mg/mL in the microbroth dilution method. Despite its own weak activity, when the coumarin was combined with the above-mentioned compounds, a strong enhancement of the antifungal effect was observed, even showing a complete inhibition in the growth of the pathogen when 1 was added at a concentration of up to 5% of its MIC value. The same level of effectiveness was observed when the synthetic antifungal agents Mancozeb and Carboxin were each combined with compounds 1-4, in which cases it became possible to decrease the effective concentrations of these commercial compounds by up to 2.5 and 3%, respectively.

Antifungal effects of different organic extracts from Melia azedarach L. on phytopathogenic fungi and their isolated active components.

Extracts from different parts of Melia azedarach L. were studied as potential antifungal agents for selected phytopathogenic fungi. In a serial agar dilution method, hexanic and ethanolic extracts from fruit, seed kernels, and senescent leaves exhibited fungistatic activity against Aspergillus flavus,Diaporthe phaseolorum var. meridionales, Fusarium oxysporum, Fusarium solani, Fusarium verticillioides, and Sclerotinia sclerotiorum. Both hexanic extract from senescent leaves and ethanolic extract from seed kernel were highly effective on all tested fungi, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 25 mg/mL and 0.5 to 5 mg/mL, respectively. In addition, all of the above-mentioned extracts showed fungicidal activity on these fungi, with ethanolic seed kernel extract being the most active. Three compounds displaying activity against F. verticillioides were isolated from the ethanolic seed kernel extract and were characterized as vanillin (1), 4-hydroxy-3-methoxycinnamaldehyde (2), and (+/-)-pinoresinol (3), with MICs of 0.6, 0.4, and 1.0 mg/mL, respectively. These compounds also showed a synergistic effect when combined in different concentrations, needing four times less concentration to reach complete inhibition in the growth of F. verticillioides.

Antifeedant and insecticide properties of a limonoid from Melia azedarach (Meliaceae) with potential use for pest management.

In the course of screening for novel naturally occurring insecticides from plants, the activity of the fruit extract of the Argentinian Melia azedarach L. (Meliaceae) and its recently described limonoid meliartenin were investigated. The antifeedant activity of the fruit extract was tested on a variety of herbivore and granivorous insects through choice tests. Sixteen of 17 species belonging to three orders consume significantly less food when treated with the extract. The bioactivity of the isolated active compound meliartenin and its interchangeable isomer 12-hydroxiamoorastatin (1) was further studied. In choice tests, compound 1 inhibited feeding of Epilachna paenulata Germ. (Coleoptera, Coccinellidae) larvae, with an ED(50) value of 0.80 microg/cm(2), comparable to that of azadirachtin (2) and lower than that of toosendanin (3) (0.72 and 3.69 microg/cm(2), respectively), both compounds used for comparison purposes. In no-choice tests, E. paenulata larvae reared on food treated with 1 or 2 ate less, gained less weight, and suffered greater mortality rates than control larvae. The activity of compound 1 was comparable to that of 2, with LD(50) values of 0.76 and 1.24 microg/cm(2), respectively, at 96 h. Shorter LT(50) values were recorded for 1 at 4 and 1 microg/cm(2) in comparison with 2. Thus, M. azedarach fruit extract and its active principle have interesting potential for use in pest control programs.