Key antifungal, antibacterial and anti-insect assays—a critical review

Antifungal activity against Fusarium oxysporum of quinolizidines isolated from three controlled-growth Genisteae plants: structure-activity relationship implications

The Genisteae tribe belongs to the Fabaceae family. The wide occurrence of secondary metabolites, explicitly highlighting the quinolizidine alkaloids (QAs), characterizes this tribe. In the present study, twenty QAs (1-20), including lupanine (1-7), sparteine (8-10), lupanine (11), cytisine and tetrahydrocytisine (12-17), and matrine (18-20)-type QAs were extracted and isolated from leaves of three species (i.e., Lupinus polyphyllus ('rusell' hybrid), Lupinus mutabilis, and Genista monspessulana) belonging to the Genisteae tribe. These plant sources were propagated under greenhouse conditions. The isolated compounds were elucidated by analyzing their spectroscopical data (MS, NMR). The antifungal effect on the mycelial growth of Fusarium oxysporum (Fox) of each isolated QA was then evaluated through the amended medium assay. The best antifungal activity was found to be for compounds 8 (IC₅₀ = 16.5 µM), 9 (IC₅₀ = 7.2 µM), 12 (IC₅₀ = 11.3 µM), and 18 (IC₅₀ = 12.3 µM). The inhibitory data suggest that some QAs could efficiently inhibit Fox mycelium growth depending on particular structural requirements deduced from structure-activity relationship scrutinies. The identified quinolizidine-related moieties can be involved in lead structures to develop further antifungal bioactives against Fox.

Toxic Potential of Cerrado Plants on Different Organisms

Cerrado has many compounds that have been used as biopesticides, herbicides, medicines, and others due to their highly toxic potential. Thus, this review aims to present information about the toxicity of Cerrado plants. For this purpose, a review was performed using PubMed, Science Direct, and Web Of Science databases. After applying exclusion criteria, 187 articles published in the last 20 years were selected and analyzed. Detailed information about the extract preparation, part of the plant used, dose/concentration tested, model system, and employed assay was provided for different toxic activities described in the literature, namely cytotoxic, genotoxic, mutagenic, antibacterial, antifungal, antiviral, insecticidal, antiparasitic, and molluscicidal activities. In addition, the steps to execute research on plant toxicity and the more common methods employed were discussed. This review synthesized and organized the available research on the toxic effects of Cerrado plants, which could contribute to the future design of new environmentally safe products.

Quinolizidine-Based Variations and Antifungal Activity of Eight Lupinus Species Grown under Greenhouse Conditions

Fusarium oxysporum is an aggressive phytopathogen that affects various plant species, resulting in extensive local and global economic losses. Therefore, the search for competent alternatives is a constant pursuit. Quinolizidine alkaloids (QA) are naturally occurring compounds with diverse biological activities. The structural diversity of quinolizidines is mainly contributed by species of the family Fabaceae, particularly the genus Lupinus. This quinolizidine-based chemo diversity can be explored to find antifungals and even mixtures to address concomitant effects on F. oxysporum. Thus, the antifungal activity of quinolizidine-rich extracts (QREs) from the leaves of eight greenhouse-propagated Lupinus species was evaluated to outline promising QA mixtures against F. oxysporum. Thirteen main compounds were identified and quantified using an external standard. Quantitative analysis revealed different contents per quinolizidine depending on the Lupinus plant, ranging from 0.003 to 32.8 mg/g fresh leaves. Bioautography showed that all extracts were active at the maximum concentration (5 µg/µL). They also exhibited >50% mycelium growth inhibition. All QREs were fungistatic except for the fungicidal QRE of L. polyphyllus Lindl. Angustifoline, matrine, 13α-hydroxylupanine, and 17-oxolupanine were ranked to act jointly against the phytopathogen. Our findings constitute reference information to better understand the antifungal activity of naturally afforded QA mixtures from these globally important plants.

Plectranthus ecklonii Benth: A Comprehensive Review Into its Phytochemistry and Exerted Biological Activities

Ethnopharmacological Relevance: Plectranthus genus (Lamiaceae family) contain several species with acknowledged ethnopharmacological uses, such as, for gastrointestinal and respiratory-related problems, due to their anti-inflammatory, antibacterial and antifungal properties. The bioactivity of isolated medicinal compounds from this genus justifies the increased interest in recent times for species of Plectranthus, placing them in the spotlight for natural product drug development. Aim of the study: To the best of our knowledge, this is the first review on the biological activities of Plectranthus ecklonii Benth. As such, the aim of this review was three-fold: 1) to summarize the chemical compounds isolated from P. ecklonii; 2) to collate the biological activities and mechanisms of action of these compounds from in vitro studies; and 3) to evaluate the documented uses and potential applications of this species, in order to postulate on the direction of pharmaceutical uses of this species. Materials and methods: An extensive database retrieval was performed using the electronic databases Web of Science, PubMed, Google Scholar and ScienceDirect. The search criteria consisted of the keywords "Plectranthus ecklonii", "Plectranthus ecklonii + review", "Plectranthus ecklonii + diterpenes" or "Plectranthus ecklonii + abietanes", "ecklonii + parviflorone D", searched individually and as combinations. Eligibility criteria were set out and titles in English, Portuguese and Spanish were reviewed, with all references included dating from 1970 to 2021. A total of 169 papers were selected and included. Chemical structures were drawn using ChemDraw 20.0, CID numbers were searched in PubChem and the PRISMA diagram was created using PowerPoint 2012. Results: To date, a total of 28 compounds have been isolated from P. ecklonii, including diterpenes, triterpenes, flavonoids, and hydroxycinnamic acids. Most focused on the antimicrobial action of its constituents, although compounds have demonstrated other bioactivities, namely antioxidant, anti-inflammatory and antitumor. The most recent studies emphasize the diterpenoids, particularly parviflorone D, with the help of nanotechnology. Conclusions: The widespread ethnobotanical and traditional uses of P. ecklonii can be scientifically justified by a range of biological activities, demonstrated by isolated secondary metabolites. These bioactivities showcase the potential of this species in the development of economically important active pharmaceutical ingredients, particularly in anticancer therapy.

Cu-BTC metal-organic framework as a biocompatible nanoporous carrier for chlorhexidine antibacterial agent

Antibacterial materials are an essential part of modern life and many efforts have been made to find a new and effective type of them. In this study, chlorhexidine (CHX) was loaded on Cu-BTC metal-organic framework (MOF), that both of them are known to have antibacterial properties. The antibacterial properties of Cu-BTC, CHX and CHX@Cu-BTC were investigated against Gram-positive and Gram-negative bacteria. Agar well-diffusion method and MIC test showed that CHX@Cu-BTC has high antibacterial activity. Characterization methods, such as FT-IR, XRD, N₂ adsorption-desorption isotherm, TGA, SEM, EDX, TEM and zeta potential, were employed to characterize their structures. Cu-BTC MOF nanoparticles were synthesized and used as nanoporous carriers for chlorhexidine. The loading was about 10%, which was absorbed into the pores. Antibacterial activity was investigated against Gram-negative and Gram-positive bacteria by Agar well diffusion method and MIC (minimal inhibitory concentration) assay. The CHX@Cu-BTC had synergistic antibacterial activity of Cu-BTC and chlorhexidine.

Bis- and mono-substituted Chalcones exert anti-feedant and toxic effects on fall armyworm Spodoptera frugiperda

Spodoptera frugiperda is a highly polyphagous migratory lepidopteran pest species. It causes infestation in crops leading to the severe crop losses. Being a new invasive parasite, its susceptibility to insecticides needs to be explored; and therefore, there is an urgent need to develop the potent insecticides for the effective control of this insect pest. To attain the crop sustainability, the antifeedant, toxicity and nutritional effects on larvae of Spodoptera frugiperda were studied with six mono- and eight bis- substituted chalcones. The antifeedant activity was calculated when 50% of the larvae control ate 50% of the diet through the FR factor. Toxicity was assessed through larval, pupal mortality and the emergence of adults and nutritional effects with consumption rates (IC), growth (GR) and consumption efficiency (EIC). The bis-chalcones 6b, 6e, 6f and 6h caused lethal effect on S. frugiperda in the first larval stages, being 6b the most toxic (85%). Adults who survived showed malformations and decreased size, which led to death. The larvae fed with aggregate in the bis-chalcones diet: 6b, 6e and 6f had the highest percentage of intake and the poorest conversion of nutrient absorption (ECI), which suggests that the larva metabolizes food for energy and results in a decrease of growth and death in early stages. Bis-chalcones showed more toxicity than mono-chalcones and 6b causes the most toxic and dietary change.

Chemical Profile of Launaea nudicaulis Ethanolic Extract and Its Antidiabetic Effect in Streptozotocin-Induced Rats

Launaea nudicaulis is used in folk medicine worldwide to treat several diseases. The present study aimed to assess the antidiabetic activity of L. nudicaulis ethanolic extract and its effect on diabetic complications in streptozotocin-induced hyperglycemic rats. The extract was orally administrated at 250 and 500 mg/kg/day for 5-weeks and compared to glibenclamide as a reference drug at a dose of 5 mg/kg/day. Administration of the extract exhibited a potential hypoglycemic effect manifested by a significant depletion of serum blood glucose concurrent with a significant elevation in serum insulin secretion. After 5-weeks, extract at 250 and 500 mg/kg/day decreased blood glucose levels by about 53.8 and 68.1%, respectively, compared to the initial values (p ≤ 0.05). The extract at the two dosages prevented weight loss of rats from the 2nd week till the end of the experiment, compared to diabetic control rats. The extract further exhibited marked improvement in diabetic complications including liver, kidney and testis performance, oxidative stress, and relative weight of vital organs, with respect to diabetic control. Histopathological examinations confirmed the previous biochemical analysis, where the extract showed a protective effect on the pancreas, liver, kidney, and testis that degenerated in diabetic control rats. To characterize extract composition, UPLC-ESI-qTOF-MS identified 85 chromatographic peaks belonging to flavonoids, phenolics, acyl glycerols, nitrogenous compounds, and fatty acids, with four novel phenolics reported. The potential anti-diabetic effect warrants its inclusion in further studies and or isolation of the main bioactive agent(s).

Structural and Microbiological Characterization of 5-Hydroxy-3,7,4'-Trimethoxyflavone: A Flavonoid Isolated from Vitex gardneriana Schauer Leaves

INTRODUCTION

Staphylococcus aureus represents the most common etiologic agent of purulent infections, affecting humans and animals. Escherichia coli is one of the principal causes of infectious diseases, mainly diarrheal diseases due to enterotoxin action. There are many reports indicating that these bacteria are multidrug-resistant (MDR) pathogens.

OBJECTIVE

In this study, we investigated the antimicrobial and modulatory activities of 5-hydroxy-3,7,4'-trimethoxyflavone (VG.EF.CLII) against E. coli and S. aureus strains.

METHODS

5-Hydroxy-3,7,4'-trimethoxyflavone was isolated from Vitex gardneriana Schauer leaves and structurally characterized using nuclear magnetic resonance. The antibacterial effect of VG.EF.CLII and modulation of antibiotic activity, both determined by minimum inhibitory concentration, were assessed using microtiter plates.

RESULTS

VG.EF.CLII showed bacterial growth inhibition at concentrations ≤512 μg/mL, and synergistic effects were observed for the modulation of two distinct antibiotic classes (the fluoroquinolone norfloxacin and the aminoglycoside gentamicin).

CONCLUSION

5-Hydroxy-3,7,4'-trimethoxyflavone isolated from V. gardneriana showed promising antimicrobial activity against MDR bacterial strains S. aureus 358 and E. coli 27 when associated with the antibiotics norfloxacin and gentamicin. Therefore, this natural product can contribute to the control of bacterial resistance.

High Resolution Assessment of Spatio-Temporal Changes in O2 Concentration in Root-Pathogen Interaction

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. lycopersici (Fol), is one of the most destructive soil-borne diseases of tomatoes. Infection takes place on the roots and the process starts with contact between the fungus and the roots hairs. To date, no detailed studies are available on metabolic activity in the early stages of the Fol and tomato root interaction. Spatial and temporal patterns of oxygen consumption could provide new insights into the dynamics of early colonization. Here, we combined planar optodes and spatial analysis to assess how tomato roots influence the metabolic activity and growth patterns of Fol. The results shows that the fungal metabolism, measured as oxygen consumption, increases within a few hours after the inoculation. Statistical analysis revealed that the fungus tends to growth toward the root, whereas, when the root is not present, the single elements of the fungus move with a Brownian motion (random). The combination of planar optodes and spatial analysis is a powerful new tool for assessing temporal and spatial dynamics in the early stages of root-pathogen interaction.

Chemical Composition and Anti-phytopathogenic Activity of the Essential Oil of Beilschmiedia miersii

Beilschmiedia miersii (Gay) Kosterm. (Lauraceae) (“Belloto del Norte”) is a little-studied tree endemic of the Central Zone of Chile. Hydrodistillation of leaves and stem bark of B. miersii yielded 0.2% essential oil. GC-MS analysis allowed identification of 31 components. The most abundant compounds were three phenylpropanoids: Sarisan (45.8%), eugenol methyl ether (27.7%) and safrole (5.8%). The oil of B. miersii showed high antioxidant content (TEAC: 750.8 ± 9.6 μmol/100 g of essential oil). The anti-phytopathogenic activity was evaluated against pathogens of plants: Fungi (Botrytis cinerea, Gibberella fujikuroi and Phytophthora cinnamomi) and bacteria: (Erwinia carotovora, Pseudomonas syringae and Agrobacterium tumefaciens). The oil showed anti-phytopathogenic activity against all tested bacteria and fungi, especially against A tumefaciens (IC50 = 5 μg / mL) and P. cinnamomi (IC50 = 200 μg / mL). This study demonstrates that the essential oil of B. miersii has great potential for applications in food and agricultural industries.

Insecticidal Effects of Acetogenins from Rollinia Occidentalis Seed Extract

From the methanol seed extract of Rollinia occidentalis five acetogenins were isolated, sylvaticin (1), rolliniastatin-1 (2), rolliniastatin-2 (3), motrilin (4) and desacetyluvaricin (5), and evaluated for their toxicity and nutritional alterations on Spodoptera frugiperda Smith (Lepidoptera: Noctuidae). All but one of the compounds produced more than 90% mortality on early larval instars at 50 and 100 μg per g of diet. Sylvaticin caused 15 and 60% mortality at 50 and 100 μg/g, respectively, while the methanol seed extract reached 35 and 50% at 100 and 250 μg/g, respectively. The addition of R. occidentalis methanolic seed extract (100 and 250 μg/g) and sylvaticin (100 μg/g) to the larval diet brought about significant changes to the nutritional indices in connection with larvae fed the control diet. This is the first report on the isolation of acetogenins from R. occidentalis and their insecticidal effects on S. frugiperda.

Bioactivity of the Essential Oil of an Argentine Collection of Acanthospermum hispidum (Asteraceae)

The essential oil of an Argentine collection of the annual herb Acanthospermum hispidum DC. (Asteraceae), which contains the sesquiterpenoids β-caryophyllene (35.2%), α-bisabolol (11.4%), and germacrene D (11.1%) as major constituents, displayed molluscicidal effects on an adult population of Biomphalaria peregrina Orbigny (LD50 37.8 μg/mL) and produced alteration of the feeding and oviposition behavior of the polyphagous insect Spodoptera frugiperda Smith when incorporated in the larval diet at 250 μg/g. In addition, a selective antibacterial activity was observed against pathogenic strains of Staphylococcus aureus and Enterococcus faecalis (MICs 62.5 and 125 μg/mL), but was inactive at 125 μg/mL against three beneficial lactic acid bacteria. Synergistic interactions were further validated by FIC index determination of the combination of the antibiotics oxacillin and gentamicin and the essential oil on the four pathogenic strains evaluated.

An introduction to planar chromatography and its application to natural products isolation

Thin-layer chromatography (TLC) is an easy, inexpensive, rapid, and the most widely used method for the analysis and isolation of small organic natural and synthetic products. It also has use in the biological evaluation of organic compounds, particularly in the areas of antimicrobial and antioxidant metabolites and for the evaluation of acetylcholinesterase inhibitors which have utility in the treatment of Alzheimer's disease. The ease and inexpensiveness of use of this technique, coupled with the ability to rapidly develop separation and bioassay protocols will ensure that TLC will be used for some considerable time alongside conventional instrumental methods. This chapter deals with the basic principles of TLC and describes methods for the analysis and isolation of natural products. Examples of methods for isolation of several classes of natural product are detailed and protocols for TLC bioassays are given.

Toxic Effects of Citrus aurantium and C. limon Essential Oils on Spodoptera frugiperda (Lepidoptera: Noctuidae)

Citrus aurantium and C. limon were selected in the search for natural plant insecticides. The essential oils of C. aurantium and C. limon and ethanol extracts of the seeds, pulp, albedo, and peel of C. aurantium were incorporated into the larval diet of the lepidopteran pest Spodoptera frugiperda. Larval and pupal mortality were quantified and adult malformation was observed. C aurantium essential oil had antifeedant action and the mixture of albedo ethanol extract and C aurantium essential oil had toxic effects on S. frugiperda larvae at early stages, when they had not yet produced major damage to the crop. Our results indicated that a mixture of ethanol extract of albedo and C. aurantium essential oil (250 μg of extract mix per g of diet) deterred feeding by 46% and had the highest larval mortality (100%) of the materials tested. The peel extract (250 μg per g of diet) produced an increment in growth rate and diet consumption. However, 40% of the larval and 45% of the pupal populations died after 96 h of treatment. The blend of essential oil and C. aurantium albedo ethanol extract showed the lowest consumption and a poor nutrient conversion into biomass. Finally, the presence of D-limonene and nootkatone in the peel ethanol extract, and C. limon and C. aurantium essential oils, may be the cause of the response in the feeding behavior and toxic effects found on S. frugiperda.

Anti-phytopathogenic activities of macro-algae extracts

Aqueous and ethanolic extracts obtained from nine Chilean marine macro-algae collected at different seasons were examined in vitro and in vivo for properties that reduce the growth of plant pathogens or decrease the injury severity of plant foliar tissues following pathogen infection. Particular crude aqueous or organic extracts showed effects on the growth of pathogenic bacteria whereas others displayed important effects against pathogenic fungi or viruses, either by inhibiting fungal mycelia growth or by reducing the disease symptoms in leaves caused by pathogen challenge. Organic extracts obtained from the brown-alga Lessonia trabeculata inhibited bacterial growth and reduced both the number and size of the necrotic lesion in tomato leaves following infection with Botrytis cinerea. Aqueous and ethanolic extracts from the red-alga Gracillaria chilensis prevent the growth of Phytophthora cinnamomi, showing a response which depends on doses and collecting-time. Similarly, aqueous and ethanolic extracts from the brown-alga Durvillaea antarctica were able to diminish the damage caused by tobacco mosaic virus (TMV) in tobacco leaves, and the aqueous procedure is, in addition, more effective and seasonally independent. These results suggest that macro-algae contain compounds with different chemical properties which could be considered for controlling specific plant pathogens.

Screening of Uruguayan plants for deterrent activity against insects

We evaluated the anti-insectan activity of extracts from different vegetative parts of ten plant species native to Uruguay. The selected plants belong to five families: Bignoniaceae: Clytostoma callistegioides, Dolichandra cynanchoides, Macfadyena unguis-cati; Sapindaceae: Dodonaea viscosa, Allophylus edulis, Serjania meridionalis; Lamiaceae: Salvia procurrens, Salvia guaranitica; Solanaceae: Lycium cestroides; and Phytolaccaceae: Phytolacca dioica. The extracts were evaluated in independent bioassays against four insect pests and one beneficial insect. Aphid settling inhibition was evaluated with a grass specialist, Rhopalosiphum padi, and a feeding generalist, Myzus persicae (both Hemiptera: Aphididae). Antifeedant activity was tested with adults of the specialist Epilachna paenulata (Coleoptera: Coccinellidae) and larvae of the generalist Spodoptera littoralis (Lepidoptera: Noctuidae). Finally, contact toxicity was assessed with honey bees, Apis mellifera (Hymenoptera: Apidae). Strong settling inhibition (SI) activity (expressed as %SI, where 100% means complete inhibition by the extract) was found only for the twig extracts of A. edulis (Sapindaceae) against M. persicae (% SI = 77 +/- 4). Antifeedant activity (expressed as % of feeding reduction (FR), where 100% means no consumption on extract-treated diet) against E. paenulata was significant for the leaf extracts of L. cestroides (Solanaceae) (% FR = 100 +/- 0) as well as of all Bignoniaceae and Sapindaceae species. No extracts were active against S. littoralis larvae, and most of them were innocuous to honey bees, with the exception of L. cestroides and S. meridionalis leaf extracts.

Purification of a lectin from Eugenia uniflora L. seeds and its potential antibacterial activity

AIMS

The aim of this work was to analyse the antimicrobial properties of a purified lectin from Eugenia uniflora L. seeds.

METHODS AND RESULTS

The E. uniflora lectin (EuniSL) was isolated from the seed extract and purified by ion-exchange chromatography in DEAE-Sephadex with a purification factor of 11.68. The purified lectin showed a single band on denaturing electrophoresis, with a molecular mass of 67 kDa. EuniSL agglutinated rabbit and human erythrocytes with a higher specificity for rabbit erythrocytes. The haemagglutination was not inhibited by the tested carbohydrates but glycoproteins exerted a strong inhibitory action. The lectin proved to be thermo resistant with the highest stability at pH 6.5 and divalent ions did not affect its activity. EuniSL demonstrated a remarkable nonselective antibacterial activity. EuniSL strongly inhibited the growth of Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella sp. with a minimum inhibitory concentration (MIC) of 1.5 microg ml(-1), and moderately inhibited the growth of Bacillus subtilis, Streptococcus sp. and Escherichia coli with a MIC of 16.5 microg ml(-1).

CONCLUSIONS

EuniSL was found to be effective against bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

The strong antibacterial activity of the studied lectin indicates a high potential for clinical microbiology and therapeutic applications.

Induction of p-coumaroyldopamine and feruloyldopamine, two novel metabolites, in tomato by the bacterial pathogen Pseudomonas syringae

Inoculation of tomato plants (Solanum lycopersicum cv. Rutgers) with Pseudomonas syringae pv. tomato led to the production of a hypersensitive-like response in this pathovar of tomato. Accumulation of hydroxycinnamic acid amides (HCAA) of tyramine (p-coumaroyltyramine and feruloyltyramine) and dopamine (p-coumaroyldopamine and feruloyldopamine) was detected after bacterial infection. Two of them, p-coumaroyldopamine and feruloyldopamine, are described for the first time. The accumulation of HCAA was preceded by an increment of hydroxycinnamoyl-CoA:tyramine N-hydroxycinnamoyl transferase (THT) gene expression. HCAA also accumulated in transgenic NahG tomato plants overexpressing a bacterial salicylic hydroxylase. However, treatment of plants with the ethylene biosynthesis inhibitor, aminoethoxyvinilglycine, led to a reduction in the accumulation of THT transcripts and HCAA. Together, the results suggest that pathogen-induced induction of ethylene is essential for HCAA synthesis, whereas salicylic acid is not required for this response. In addition, notable antibacterial and antioxidant activities were found for the new HCAA, thus indicating that they could play a role in the defense of tomato plants against bacterial infection.

Oxygen consumption-based evaluation of fungal activity

A novel oxygen-based microplate assay for studying fungal activity is described. Fungal activity results in a change of oxygen concentration in CVC-96 plates and thus produces a signal that enables continuous monitoring of fungal activity. In this study the oxygen consumption was different for three tested fungi, Fusarium oxysporum f. sp. lycopersici, Verticillium dahliae and Trichoderma longibrachiatum. The assay described is a highly sensitive and reliable method for monitoring fungal activity. This assay does not interfere with fungal development and there is no need to kill the cells to take a measurement. This test would be useful for studying reactions that consume oxygen so possible applications of this test could be physiological studies, testing of fungicidal or fungistatic compounds, and studying enzyme reactions. The system provides a valuable insight into the kinetics of fungal activity and is suitable to test other systems.

Anti-infective potential of natural products: how to develop a stronger in vitro 'proof-of-concept'

Natural products, either as pure compounds or as standardized plant extracts, provide unlimited opportunities for new drug leads because of the unmatched availability of chemical diversity. To secure this, a number of pivotal quality standards need to be set at the level of extract processing and primary evaluation in pharmacological screening models. This review provides a number of recommendations that will help to define a more sound 'proof-of-concept' for antibacterial, antifungal, antiviral and antiparasitic potential in natural products. An integrated panel of pathogens is proposed for antimicrobial profiling, using accessible standard in vitro experimental procedures, endpoint parameters and efficacy criteria. Primary requirements include: (1) use of reference strains or fully characterized clinical isolates, (2) in vitro models on the whole organism and if possible cell-based, (3) evaluation of selectivity by parallel cytotoxicity testing and/or integrated profiling against unrelated micro-organisms, (4) adequately broad dose range, enabling dose-response curves, (5) stringent endpoint criteria with IC(50)-values generally below 100microug/ml for extracts and below 25microM for pure compounds, (6) proper preparation, storage and in-test processing of extracts, (7) inclusion of appropriate controls in each in vitro test replicate (blanks, infected and reference controls) and (8) follow-up of in vitro activity ('hit'-status) in matching animal models ('lead'-status).

1H and 13C NMR signal assignments of a novel Baeyer-Villiger originated diterpene lactone

A highly rearranged novel dilactone was the single product isolated from Baeyer-Villiger oxidation of a norketone prepared from grandiflorenic acid, a natural kaurane diterpene. The complete 1H and 13C NMR assignment is presented for this novel compound that showed discrete in vitro antibacterial activity.

Cytotoxic clerodane diterpenes from Glossocarya calcicola

Three clerodane diterpenes were isolated and identified from leaf extract of Glossocarya calcicola. Compound has been characterised as (rel)-10betaH-trans-12xi-(2-methylbut-2(E)-enoyl)-1beta-(isobutanoyl)-6alpha,13xi-dihydroxyclerodan-4(20),8(18)-dien-7,15-dione-15,16-oxide, to which we have assigned the trivial name calcicolin-A. The other two compounds had the same skeletal structure and C-12 substituent but in compound, the C-1 esterifying group becomes 2-methylbut-2(E)-enoic acid and in it becomes 2-methylbutanoic acid. Although anti-insect activity was not observed for G. calcicola, cytotoxicity against insect and human carcinoma cell lines was detected.

Antibacterial activity of seed proteins of Robinia pseudoacacia

A low molecular weight cationic peptide was isolated from Robinia pseudoacacia seed and tested in vitro against seven bacteria (Corynebacterium michiganense, Staphylococcus aureus, Bacillus subtilis, Erwinia carotovora subsp. carotovora, Pseudomonas syringae pv syringae, Xanthomonas campestris pv campestris, and Escherichia coli). The peptide inhibited the growth of the tested strains. The effective concentrations required for 50% inhibition of bacterial growth ranged between 20 and 120 microg ml(-1) protein. S. aureus was found to be the most sensitive strain, however, E. coli was not affected much when compared with others. Reduction of antibacterial activity of the peptide with CaCl2 addition into the growth medium was also observed.

Antimicrobial activity of extracts and some compounds from Calea platylepis

The antimicrobial activity of dichloromethane extracts (leaves, flowers and underground parts) and some compounds isolated from Calea platylepis were evaluated by the well diffusion method.

Trypanocidal and antimicrobial activities of Moquinia kingii

A chloroform crude extract (aerial part) and two compounds, apigenin (1) and cynaropicrin (2), isolated from Moquinia kingii were evaluated against Trypanosoma cruzi trypomastigotes in vitro. Antimicrobial activity was also screened using twenty-two strains including gram-positive and gram-negative bacteria and the yeasts Candida albicans and C. tropicalis. The chloroform crude extract, fractions and isolated compounds from M. kingii were active for both activities. The IC50 values for trypanocidal activity obtained for cynaropicrin and apigenin were 93.5 microg/ml and 181 microg/ml, respectively, while the minimum inhibitory concentrations (MICs) varied from 100 microg/ml to 2500 microg/ml, against the strains of bacteria and yeasts evaluated.

In vitro activity of Brazilian medicinal plants, naturally occurring naphthoquinones and their analogues, against methicillin-resistant Staphylococcus aureus

Fourteen extracts from Brazilian traditional medicinal plants used to treat infectious diseases were used to look for potential antimicrobial activity against multiresistant bacteria of medical importance. Staphylococcus aureus strains were susceptible to extracts of Punica granatum and Tabebuia avellanedae. The minimum inhibitory concentrations (MICs) of the total extracts and of additional fractions of these plants were determined by employing strains of methicillin-resistant (MRSA) and -sensitive (MSSA) S. aureus, including isolates of the PFGE clone A, which is prevalent in Brazil and two ATCC reference strains. A mixture of ellagitannins isolated from P. granatum and two naphthoquinones isolated from T. avellanedae demonstrated antibacterial activity against all S. aureus strains tested. Semi-synthetic furanonaphthoquinones (FNQs) showed lower MICs than those exhibited by natural occurring naphthoquinones. The results indicate that these natural products can be effective potential candidates for the development of new strategies to treat MRSA infections.

Bioactivity of crude extracts and some constituents of Blutaparon portulacoides (Amaranthaceae)

Crude extracts (aerial parts and roots, both dried), methylenedioxyflavonol, and a mixture of acyl steryl glycosides isolated from Blutaparon portulacoides, were assayed for their toxicity against Trypanosoma cruzi trypomastigotes and Leishmania amazonensis amastigotes from axenic cultures. The antimicrobial activity was also investigated, in a screening conducted using fifteen strains of Gram-positive and Gram-negative bacteria, along with the yeasts, Candida albicans and Candida tropicalis. To assess the antibacterial activity of the isolated compounds, the minimum inhibitory concentrations (MICs) were determined. There are no reports of acyl steryl glycosides in the genus Blutaparon and their biological activities are being evaluated for the first time.

The genus Hypericum--a valuable resource of anti-Staphylococcal leads

In the present study, extracts of 34 species and varieties of the genus Hypericum were screened for activity against a clinical isolate of methicillin-resistant Staphylococcus aureus, which in addition possessed a multidrug efflux mechanism conferring a high level of resistance to therapeutically useful antibiotics. Thirty-three of the 34 chloroform extracts showed significant activity in a disk diffusion assay, and five extracts had minimum inhibitory concentrations of 64 microg/ml, indicating that this genus has great potential to yield compounds with potent activity against multidrug-resistant bacteria.

Medicinal plants in the healing of dry socket in rats: microbiological and microscopic analysis

The effectiveness of medicinal herbs as antimicrobial agents was tested on isolated microorganisms from an induced alveolitis and on alveolitis in rats. Sixteen ethanolic extracts from plants were prepared and tested. The plant materials were selected from ethnobotanic data and the best result was obtained with Schinus terebinthifolius Raddi. The activity on Enterococcus, Bacillus corineforme, Streptococcus viridans and S. beta-hemolytic was better than the one presented by the antibiotic currently used for the treatment of alveolitis. The extract of Schinus terebinthifolius Raddi has shown good wound-healing activity by histological analysis.

Screening antifungal activities of selected medicinal plants

Plants synthesise a vast array of secondary metabolites that are gaining importance for their biotechnological applications. The antifungal activity of the ethanolic extracts of ten Argentinean plants used in native medicine is reported. Antifungal assays included radial growth inhibition, disk and well diffusion assays and growth inhibition by broth dilution tests. The chosen test fungi were yeasts, microfungi and wood-rot causing Basidiomycetes. Extracts of Larrea divaricata, Zuccagnia punctata and Larrea cuneifolia displayed remarkable activity in the assays against the majority of the test fungi. In addition to the former plants, Prosopanche americana also inhibited yeast growth.

Prenylated phenylpropenes from Coleonema pulchellum with antimicrobial activity

The lipophilic root extract of Coleonema pulchellum was analysed and tested for antifungal and antibacterial activity. Eight previously undescribed prenyloxy and geranyloxy phenylpropenes, were isolated as major compounds together with the known evofolin-C as well as the lignans (+/-)-sesamin and (+/-)-prenylpiperitol, the diterpene (-)-pimara-9(11),15-dien-19-oic acid and the 2,4-decadienoic acid isobutylamide. All structures were established by spectroscopic evidence. From the new phenylpropenes, named evofolin-C-acetate, colenemol, colenemal, prenycol acetate, dehydroprenycol acetate, precolpuchol, colpuchol and colpuchol acetate, the dihydroxylated precolpuchol displayed the strongest antifungal and antibacterial activity against Cladosporium herbarum and Staphylococcus aureus, respectively.