Synthesis, Characterization, X-ray Molecular Structure, Antioxidant, Antifungal, and Allelopathic Activity of a New Isonicotinate-Derived meso-Tetraarylporphyrin.

The present article describes the synthesis of an isonicotinate-derived meso-arylporphyrin, that has been fully characterized by spectroscopic methods (including fluorescence spectroscopy), as well as elemental analysis and HR-MS. The structure of an n-hexane monosolvate has been determined by single-crystal X-ray diffraction analysis. The radical scavenging activity of this new porphyrin against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical has been measured. Its antifungal activity against three yeast strains (C. albicans ATCC 90028, C. glabrata ATCC 64677, and C. tropicalis ATCC 64677) has been tested using the disk diffusion and microdilution methods. Whereas the measured antioxidant activity was low, the porphyrin showed moderate but encouraging antifungal activity. Finally, a study of its effect on the germination of lentil seeds revealed interesting allelopathic properties.

Vacuum fractional distillation of Cunila galioides Benth. essential oil: chemical composition and biological activities of raw oil and its fractions.

This work aimed to rectify Cunila galioides essential oil and evaluate the raw oil and the fractions' antifungal, allelopathic, and antioxidant activities. The results showed that the raw essential oil and the bottom fraction were primarily composed of linalyl propionate (42.9 wt.% and 60.2 wt.%). The top fraction was composed mainly of limonene (45.7 wt.%). The antioxidant activity changed with the radical and the fraction. The bottom had a weaker antifungal effect than the raw oil and the top. Nevertheless, the essential oil and the fractions had a similar antifungal activity at 0.50 % v/v and higher. Similar behavior was observed for the allelopathic tests. No difference occurred between the raw oil and the fractions, with reduced germination percentages and speed at 0.25 % v/v and complete inhibition at 0.50 % v/v. The oil can be rectified, and the fractions may be used without harming their biological activity.

Chemical Composition, Repellent, and Phytotoxic Potentials of the Fractionated Resin Essential Oil from Araucaria heterophylla Growing in Tunisia.

The resin essential oil (REO) of the Tunisian Araucaria heterophylla trunk bark was investigated for its chemical composition. Then, it was evaluated for its insecticidal and allelopathic activities. The REO was obtained by hydrodistillation for 9 h (yield of 4.2 % w/w). Moreover, fractional hydrodistillation was carried out at 3-hour intervals, resulting in 3 fractions (R1-R3), to facilitate chemical identification and localization of the aforementioned biological activities. GC/MS analysis of the obtained samples allowed the identification of 25 compounds, representing between 91.2 and 96.3 % of their total constituents, which consisted predominantly of sesquiterpene hydrocarbons, oxygenated sesquiterpenes and diterpene hydrocarbons. α-Copaene (10.8 %), γ-muurolene (5.8 %), α-copaen-11-ol (7.8 %), spathulenol (10.5 %), 15-copaenol (8.2 %), ylangenal (10.3 %), dehydrosaussurea lactone (7.7 %), and sandaracopimaradiene (11.4 %) were identified as major compounds. The second part aimed to assess the impact of the A. heterophylla EO and its three fractions for their insecticidal and repellent activity against Tribolium castaneum (Herbst), a stored grain pest, of which a strong repellent activity was noted. In addition, the studied samples showed high phytotoxic effects against Lactuca sativa. The third fraction (R3) performed a total inhibitory potential on seed germination and seedling growth of the target plant. Furthermore, alongside this discovery, an estimation was conducted through molecular docking analysis. Wherein the main compounds of the studied samples were docked into the active pocket of protoporphyrinogen IX oxidase (PDB: 1SEZ), a key enzyme in chlorophyll biosynthesis. Thus, it is recommended to use the REO of A. heterophylla as a natural herbicide.

Leaf Extracts of Invasive Woody Species Demonstrate Allelopathic Effects on the Growth of a Lawn Grass Mixture.

Biochemical composition was studied in the leaf litter of alien woody species included in the 100 most aggressive invasive species of Europe: Ailanthus altissima, Quercus rubra, Acer negundo, Robinia pseudoacacia, and Elaeagnus angustifolia. Using GC-MS, we detected 187 metabolites in the leaf litter, which are phenolic acids and their derivatives, carbohydrates and their derivatives, polyphenolic compounds, cyclic esters, glycosides, and amino acids and their derivatives. Species-specific metabolites were identified for each species. The main allelochemicals in the leaf litter extract of Q. rubra are determined mainly by the relative abundance of phenolic and fatty acids and their esters, whereas those in the leaf litter extract of R. pseudoacacia are determined by carbohydrates and their derivatives and ester of fatty acid, and those in the leaf litter extract of A. altissima are determined by glycosides. Profiles of macro- and microelements were characterized. It was found that aqueous extracts of leaf litter from all the invasive woody plants under study have a negative effect on the seed germination and initial growth of Vicia cracca and Avena strigosa used for the reclamation of disturbed urban and industrial lands. At the same time, V. cracca is potentially more sensitive.

Phenolic compounds and bioactive extract produced by endophytic fungus Coriolopsis rigida.

Coriolopsis rigida was isolated as an endophytic fungus from the medicinal plant Cochlospermum regium, and their production of secondary metabolites has not yet been investigated. Thus, the endophyte was cultivated on rice solid media to evaluate its ability to produce bioactive compounds and then the chloroform extract was obtained. Two phenolic compounds, tyrosol (1) and a new natural product p-hydroxyphenylacetamide (2), were isolated from the extract. The structures of the compounds were elucidated mainly by NMR. The extract showed potent antioxidant activity with an efficient concentration (EC50) value of 0.33 mg mL-1. Additionally, demonstrated allelopathic activity inhibited the seedling growth of Lactuca sativa L. and Raphanus sativus L. by 63% and 55%, respectively.

Relationship between the Antioxidant Activity and Allelopathic Activities of 55 Chinese Pharmaceutical Plants.

Pharmaceutical plants contain several phytochemicals that are sources of myriad biological activities. These biological activities can be explored in multiple fields for the benefit of mankind. Pharmaceutical plants with high ethnobotanical indices (i.e., use value and relative frequency of citation) were reported with the potential to inhibit lettuce elongation through leachates and volatiles. The focus of the study was to assess Chinese pharmaceutical plants for both antioxidants, as well as allelopathic potentials to explore any underlying relationship. The estimation of antioxidative capacity and content of total phenolics (TPC) for the 55 Chinese pharmaceutical plants was conducted by the assays of DPPH radical scavenging activity (DPPH-RSA), oxygen radical absorbance capacity (ORAC) and the means of Folin−Ciocalteu. The estimation of the activity of allelopathy for collected medicinal plants was done by adopting the sandwich method for plant leachates and the dishpack method for volatile constituents, respectively. The fruits of sea buckthorn (Hippophae rhamnoides) had the most remarkable ORAC value (168 ± 7.04 µmol TE/g) and DPPH radical scavenging activity (440 ± 7.32 µmol TE/g) and contained the highest contents of total phenolic compounds (236 ± 7.62 mg GAE/g) in the 55 pharmaceutical plant species according to the results. In addition, sea buckthorn showed dominant allelopathic potential through plant leachates evaluated by using the sandwich method. Star anise (Illicium verum Hook. f.) showed conspicuous allelopathic activity through plant volatiles assessed by the dishpack bioassay method. Among the same plant species, antioxidative ability and total phenolics, in comparison with potential allelopathy of medicinal herbs indicated that volatile allelochemical had a weak active effect (r = 0.407 to 0.472, p < 0.01), with antioxidant capacity by the dishpack method. However, the evaluation by the sandwich method showed a significant positive correlation (r = 0.718 to 0.809, p < 0.001) with antioxidant capacity. Based on these results, a new hypothesis is that the antioxidant activity of plants may have an involvement with the potential allelopathic activity.

Analysis of Plant-Plant Interactions Reveals the Presence of Potent Antileukemic Compounds.

A method to identify anticancer compounds in plants was proposed based on the hypothesis that these compounds are primarily present in plants to provide them with an ecological advantage over neighboring plants and other competitors. According to this view, identifying plants that contain compounds that inhibit or interfere with the development of other plant species may facilitate the discovery of novel anticancer agents. The method was developed and tested using Magnolia grandiflora, Gynoxys verrucosa, Picradeniopsis oppositifolia, and Hedyosmum racemosum, which are plant species known to possess compounds with cytotoxic activities. Plant extracts were screened for growth inhibitory activity, and then a thin-layer chromatography bioautography assay was conducted. This located the major antileukemic compounds 1, 2, 4, and 5 in the extracts. Once the active compounds were located, they were extracted and purified, and their structures were determined. The growth inhibitory activity of the purified compounds showed a significant correlation with their antileukemic activity. The proposed approach is rapid, inexpensive, and can easily be implemented in areas of the world with high biodiversity but with less access to advanced facilities and biological assays.

Assessment of allelopathic activity of Tradescantia spathacea Sw. for weed control.

Tradescantia spathacea Sw. (Commelinaceae) is widely cultivated as an ornamental and medicinal plant in Southeast Asia, and its pharmacological properties are well known. On the other hand, this plant species is classified as an invasive weed in some countries. As a noxious weed, T. spathacea has been reported to disrupt the growth of native plants. However, no study has reported on its allelopathic activity. Thus, we investigated the allelopathic property and inhibitory substance of T. spathacea. The extracts of T. spathacea significantly inhibited the shoots and roots of alfalfa (Medicago sativa L.), cress (Lepidium sativum L.), lettuce (Lactuca sativa L.), barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), Italian ryegrass (Lolium multiflorum Lam.), and timothy (Phleum pratense L.) at concentrations ≥ 3 mg dry weight (D.W.) equivalent extract/mL. As the extract concentration increased, the growth of the shoots and roots decreased. The I50 values of the test plant shoots and roots were 11.6-72.4 and 5.4-19.5 mg D.W. equivalent extract/mL, respectively. The extracts were purified by column chromatography, and an inhibitory substance was separated, which inhibited the shoots and roots of cress to 18.8 and 11.6% of control growth, respectively. The results of present findings indicate that T. spathacea extracts possess an allelopathic property, and its inhibitory substance may contribute this activity.

Allelopathic activity of some Sri Lankan seaweed extracts and the isolation of a new brominated nonaromatic isolaurene type sesquiterpene from red alga Laurencia heteroclada harvey.

This study investigated the allelopathic activity of sixteen seaweed extracts using lettuce seed germination bioassay. The results of the preliminary investigation suggested that the methanol extracts of seven seaweeds demonstrated significant properties inhibitory to seed germination. In addition, chemical investigation of an active extract of the alleopathic Laurencia heteroclada Harvey led to the isolation of four known compounds as well as a new brominated nonaromatic isolaurene type sesquiterpene. The structural elucidation of pure compounds was carried out using spectroscopic methods and by comparison with literature. As seaweeds are highly abundant around Sri Lanka, they could be developed as an ecofriendly natural herbicide in their crude form.

Effects of mixtures of allelopathic plant water extracts and a herbicide on weed suppression.

The present study investigated integrated effects of two allelopathic plant water extracts (WE) (Ambrosia artemisiifolia [AMBEL] and Xanthium strumarium [XANST]) and a herbicide (mesotrione) on morphological (height and fresh weight of plants) and physiological (pigments content) parameters of Abutilon theophrasti and Chenopodium album. Also, the study aimed to identify the main components of AMBEL and XANST WE and to evaluate their potential allelopathic effects. Of the 18 investigated compounds, 13 were detected in both tested WE, and p-coumaric acid was the leading component in AMBEL, while quinic acid was the predominant component of XANST. The WE of both weed species and their mixtures with the herbicide exhibited more powerful allelopathic effects on fresh weight and content of pigments than on the height of A. theophrasti and C. album. The results showed that all measured parameters of both weeds were inhibited in treatments with mesotrione and its mix with AMBEL and XANST WE. The data revealed a highly significant difference in effects (P < 0.05) between control weeds and those treated with AMBEL WE and mesotrione, where the inhibition of fresh weight was over 90%, while the inhibition of pigments content exceeded 80%, and plant height was inhibited by over 70%.

Establishment of Pluripotent Cell Cultures to Explore Allelopathic Activity of Coffee Cells by Protoplast Co-Culture Bioassay Method.

We focused on the demonstration of a new pluripotent coffee cell culture system to control the growth and metabolic functions. Somatic cells in the epidermal layer of in vitro somatic embryos (SEs) of Coffea canephora expressed higher pluripotency to produce secondary SEs than primary or secondary meristematic tissue. SEs were ideal explants to selectively induce functionally-differentiated cell lines, both non-embryogenic callus (nEC) and embryogenic callus (EC). The protoplast co-culture bioassay method was used to explore allelopathic activity of these cultured coffee cells. Cell wall formation of lettuce protoplasts varied after five days of co-culture. A strong stimulative reaction was observed at lower nEC protoplast densities, whereas growth was inhibited at higher densities. The reaction of lettuce protoplasts after 12 days of co-culture was recognized as an inhibitory reaction of colony formation.

The possible role of toxigenic fungi in ecotoxicity of two contrasting oil-contaminated soils - A field study.

Long-term field experiments were performed to evaluate the phytotoxic properties of fungal metabolites in oil-contaminated soil and to assess the impact of contamination on the allelopathic activity of soil mycobiota. Two contrasting soils of Northwest Russia (sandy and loamy podzols) exposed to oil contamination underwent changes in abundance and allelopathic activities of soil fungi. Shifts within the microbial community caused by oil contamination affected not only oil-decomposition rates but also ecotoxicity of contaminated soil. There were significant differences in soil toxicity dynamics between sandy and loamy podzols. Four years after contamination, ecotoxicity of loamy podzol decreased, whereas sandy podzol remained highly toxic even nine years after contamination. The abundance and allelopathic activity of fungi is correlated with hydrocarbon degradation dynamics. The soil fungal community demonstrated high allelopathic activity which decreased over time in fertile loamy podzolic soil, whereas in poor sandy podzolic soil it remained high over the nine-year monitoring period. The results illustrate how oil contamination may influence allelopathic interactions in soil and demonstrate the advantage of using fungal metabolite toxicity test for testing of oil-contaminated soil samples.

Antioxidant, antimicrobial and phytotoxic activities of Rhaponticum acaule DC essential oil

The in-vitro antioxidant activity of Rhaponticum acaule essential oil (RaEO) was evaluated using ß-carotene/linoleic acid bleaching, chelating activity, and lipid peroxidation inhibition (TBARS) assays. The antimicrobial activity of RaEO was assessed by disc diffusion and microdilution methods against 8 bacteria and 4 yeast. Finally, the allelopathic activity of RaEO on the seed germination and the shoot and root elongation of lettuce (Lactuca sativa L.) seedlings were investigated. According to our results, the RaEO exhibited significant antioxidant activity, similar to those of standards (BHT and ascorbic acid) with IC50 values of 0.042 and 0.045 mg/mL obtained by ß-carotene bleaching and TBARS assays, respectively. On the other hand, despite its interesting ferrous chelating activity, RaEO possesses moderate IC50 value (0.35 mg/mL) as compared with that of EDTA (0.015 mg/mL). RaEO exhibited a strong antimicrobial activity against all the tested microorganisms, with IZ, MIC and MBC values being in the range of 7.67 ± 0.58 to 13.33 ± 0.58 mm, 1.25 to 5.00 and 5.00 to 10.00 mg/mL, respectively. The results reveled also that RaEO inhibited the shoot and root growth of Lactuca sativa L. seedlings. Our data suggested that the RaEO had pharmaceutical benefits and could be used as a potential natural herbicide resource

Isolation and Purification of Bioactive Compounds from the Stem Bark of Jatropha podagrica.

This paper reports the successive isolation and purification of bioactive compounds from the stem bark of Jatropha podagrica, a widely known medicinal plant. The ethyl acetate extract of the stem bark exhibited the strongest antioxidant activity assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, and ferric reducing antioxidant power (FRAP) assays (IC50 = 46.7, 66.0, and 492.6, respectively). By column chromatography (CC) with elution of hexane and ethyl acetate at 8:2, 7:3, and 6:4 ratios, the isolation of this active extract yielded five fractions (C1⁻C5). Chemical structures of the constituents included in C1⁻C5 were elucidated by gas chromatography-mass spectrometry (GC-MS), electrospray ionization-mass spectrometry (ESI-MS), and nuclear magnetic resonance (NMR) and resolved as methyl gallate (C1, C2, C3, C4), gallic acid (C1, C2), fraxetin (C2, C3, C4, C5), and tomentin (C3). Mixture C2 (IC50 DPPH and ABTS = 2.5 µg/mL) and C3 (IC50 FRAP = 381 µg/mL) showed the highest antioxidant properties. Among the isolated fractions, C4 was the most potential agent in growth inhibition of six bacterial strains including Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Bacillus subtilis, and Proteus mirabilis (MIC = 5, 20, 30, 20, 25, and 20 mg/mL, respectively). All identified constituents exerted an inhibitory activity on the growth of Lactuca sativa, of which the mixture C3 performed the maximal inhibition on shoot (IC50 = 49.4 µg/mL) and root (IC50 = 47.1 µg/mL) growth. Findings of this study suggest that gallic acid, methyl gallate, fraxetin, and tomentin isolated from J. podagrica possessed antioxidant, antibacterial, and growth inhibitory potentials.

Phytochemical Analysis and Potential Biological Activities of Essential Oil from Rice Leaf.

Although many investigations on phytochemicals in rice plant parts and root exudates have been conducted, information on the chemical profile of essential oil (EO) and potent biological activities has been limited. In this study, chemical compositions of rice leaf EO and in vitro biological activities were investigated. From 1.5 kg of fresh rice leaves, an amount of 20 mg EO was obtained by distillation and analyzed by gas chromatography-mass spectrometry (GC-MS), electrospray ionization (ESI), and atmospheric pressure chemical ionization (APCI) to reveal the presence of twelve volatile constituents, of which methyl ricinoleate (27.86%) was the principal compound, followed by palmitic acid (17.34%), and linolenic acid (11.16%), while 2-pentadecanone was the least (2.13%). Two phytoalexin momilactones A and B were first time identified in EO using ultra-performance liquid chromatography coupled with electrospray mass spectrometry (UPLC/ESI-MS) (9.80 and 4.93 ng/g fresh weight, respectively), which accounted for 7.35% and 3.70% of the EO, respectively. The assays of DPPH (IC50 = 73.1 µg/mL), ABTS (IC50 = 198.3 µg/mL), FRAP (IC50 = 700.8 µg/mL) and ß-carotene oxidation (LPI = 79%) revealed that EO possessed an excellent antioxidant activity. The xanthine oxidase assay indicated that the anti-hyperuricemia potential was in a moderate level (IC50 = 526 µg/mL) as compared with the standard allopurinol. The EO exerted potent inhibition on growth of Raphanus sativus, Lactuca sativa, and two noxious weeds Echinochloa crus-galli, and Bidens pilosa, but in contrast, the growth of rice seedlings was promoted. Among the examined plants, the growth of the E. crus-galli root was the most inhibited, proposing that constituents found in EO may have potential for the control of the problematic paddy weed E. crus-galli. It was found that the EO of rice leaves contained rich phytochemicals, which were potent in antioxidants and gout treatment, as well as weed management. Findings of this study highlighted the potential value of rice leaves, which may provide extra benefits for rice farmers.

Chemical Composition and Allelopathic, Phytotoxic and Pesticidal Activities of Atriplex cana Ledeb. (Amaranthaceae) Essential Oil.

The chemical composition and allelopathic, phytotoxic and pesticidal activities of Atriplex cana Ledeb. (Amaranthaceae) essential oil were investigated. Nineteen compounds were identified via GC/MS, representing 82.3 % of the total oil, and the most abundant constituents were dibutyl phthalate (21.79 %), eucalyptol (20.14 %) and myrtenyl acetate (15.56 %). The results showed that volatile organic compounds (VOCs) released by A. cana significantly inhibited seedling growth of Amaranthus retroflexus L. and Poa annua L., and 80 g of fresh stems and leaves of A. cana in a 1.5 L airtight container almost completely suppressed the seed germination of both plants. Meanwhile, 5 µg/mL essential oil completely inhibited the seed germination of A. retroflexus, Medicago sativa L., P. annua and Echinochloa crusgalli L. Pesticidal testing revealed that the essential oil had strong behavioral avoidance and lethal effects on Aphis pomi DeGeer. Five microliters of essential oil/Petri dish treatment resulted in an 84.5 % mortality rate after 12 h, and the mortality rate reached nearly 100 % after 48 h. This report is the first one on the chemical composition as well as the biological activity of the essential oil of A. cana, and our results indicate that the oil is valuable in terms of being further exploited as a bioherbicide/insecticide.

Chemical and Biological Evaluation of Essential Oils from Cardamom Species.

To highlight the importance of the spices in the Mediterranean diet, the aim of the paper was to study the essential oil compositions and to clarify the potential differences in the biological activities of the three cardamom species. In the study, we compared the phytochemical profiles and biological activities of essential oils from Elettaria cardamomum, Aframomum corrorima and Amomum subulatum. The oils were analyzed using the GC and GC/MS techniques and were mainly constituted of the oxygenated monoterpenes which represents 71.4%, 63.0%, and 51.0% of all compounds detected in E. cardamomum, A. corrorima and A. subulatum essential oils, respectively, 1,8-cineole was the main common compound between the tree tested volatile oil. The essential oils showed significant antimicrobial activity against Gram-positive and Gram-negative microorganisms tested especially the fungal strains. The Ethiopian cardamom was the most active essential oil with fungal growth inhibition zone ranging from 12.67 to 34.33 mm, MICs values ranging from 0.048 to 0.19 mg/mL, and MBCs values from 0.19 to 1.75 mg/mL. The three tested essential oils and their main component (1,8-cineole) significantly increased the production of elastase and protease production, and motility in P. aeruginosa PAO1 in a dose dependent manner. In fact, at 10 mg/mL concentration, the three essential oils showed more than 50% of inhibition of elastolytic and proteolytic activities in P. aeruginosa PAO1. The same oils inhibited also the violacein production in C. violaceum strain. It was also noticed that at high concentrations, the A. corrorima essential oil significantly inhibited the germination of radish. A thorough knowledge of the biological and safety profiles of essential oils can produce applications of economic importance.

Synthesis of a new allelopathic agent from the biotransformation of ent-15α-hydroxy-16-kauren-19-oic acid with Fusarium proliferatum.

The use of kaurane diterpenes as substrates in fungal biotransformation to achieve bioactive compounds has been widely reported. In this work, the natural product kaurenoic acid, a diterpene widely distributed in the plant Kingdom, was chemically converted into ent-15α-hydroxy-kaur-16-en-19-oic acid (1). Substrate 1 was subjected to biotransformation by the fungus Fusarium proliferatum, furnishing a new derivative, ent-2α,15α-dihydroxy-kaur-16-en-19-oic acid (2). The structure of metabolite 2 was deduced on the basis of spectroscopy and MS data. Derivative 2 showed allelopathic activity on germination and growth of root and stem of lettuce (Lactuca sativa), inhibiting 100% of germination and growth of roots and stem, at higher concentration assayed (10-4 mol/L).

Evaluation of the Allelopathic Potential of Leaf, Stem, and Root Extracts of Ocotea pulchella Nees et Mart.

Despite the increase in recent decades in herbicide research on the potential of native plants, current knowledge is considered to be low. Very few studies have been carried out on the chemical profile or the biological activity of the Brazilian savanna (Cerrado) species. In the study reported here, the allelopathic activity of AcOEt and MeOH extracts of leaves, stems, and roots from Ocotea pulchella Nees was evaluated. The extracts were assayed on etiolated wheat coleoptiles. The AcOEt leaf extract was the most active and this was tested on standard target species (STS). Lycopersicon esculentum and Lactuca sativa were the most sensitive species in this test. A total of eleven compounds have been isolated and characterized. Compounds 1, 2, 4, and 6 have not been identified previously from O. pulchella and ocoteol (9) is reported for the first time in the literature. Eight compounds were tested on wheat coleoptile growth, and spathulenol, benzyl salicylate, and benzyl benzoate showed the highest activities. These compounds showed inhibitory activity on L. esculentum. The values obtained correspond to the activity exhibited by the extract and these compounds may therefore be responsible for the allelopathic activity shown by O. pulchella.

Bio-guided optimization of the ultrasound-assisted extraction of compounds from Annona glabra L. leaves using the etiolated wheat coleoptile bioassay.

A bio-guided optimization of the extraction of bioactive components from Annona glabra leaves has been developed using the etiolated wheat coleoptile bioassay as the control method. The optimization of an ultrasound-assisted extraction of bioactive compounds using allelopathy results as target values has been carried out for the first time. A two-level fractional factorial experimental design was applied to optimize the ultrasound-assisted extraction. The solvent was the extraction variable that had the most marked effect on the resulting bioactivity of the extracts in the etiolated wheat coleoptile bioassay. Extraction time, extraction temperature and the size of the ultrasonic probe also influenced the bioactivity of the extracts. A larger scale extraction was carried out in the next step in the allelopathic study, i.e., the isolation of compounds from the bioactive extract and chemical characterization by spectroscopic techniques, including NMR. Eight compounds were isolated and identified from the active extracts, namely two steroids (ß-sistosterol and stigmasterol), five diterpenes with the kaurane skeleton (ent-kaur-16-en-19-oic acid, ent-19-methoxy-19-oxokauran-17-oic acid, annoglabasin B, ent-17-hydroxykaur-15-en-19-oic acid and ent-15ß,16ß-epoxy-17-hydroxy-kauran-19-oic acid) and the acetogenin asimicin. The most active compound was annoglabasin B, which showed inhibition with values of -95% at 10(-3) M, -87% at 5×10(-4) M and greater than -70% at 10(-4) M in the etiolated wheat coleoptile bioassay.