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15 pages, 832 KiB

Open AccessArticle

Generation of Aurachin Derivatives by Whole-Cell Biotransformation and Evaluation of Their Antiprotozoal Properties

by Sebastian Kruth, Cindy J.-M. Zimmermann, Katharina Kuhr, Wolf Hiller, Stephan Lütz, Jörg Pietruszka, Marcel Kaiser and Markus Nett

Molecules 2023, 28(3), 1066; https://doi.org/10.3390/molecules28031066 - 20 Jan 2023

Cited by 1 | Viewed by 1918

Abstract

The natural product aurachin D is a farnesylated quinolone alkaloid, which is known to possess activity against the causative agent of malaria, Plasmodium spp. In this study, we show that aurachin D inhibits other parasitic protozoa as well. While aurachin D had only [...] Read more.

The natural product aurachin D is a farnesylated quinolone alkaloid, which is known to possess activity against the causative agent of malaria, Plasmodium spp. In this study, we show that aurachin D inhibits other parasitic protozoa as well. While aurachin D had only a modest effect on Trypanosoma brucei rhodesiense, two other trypanosomatids, T. cruzi and Leishmania donovani, were killed at low micromolar and nanomolar concentrations, respectively, in an in vitro assay. The determined IC₅₀ values of aurachin D were even lower than those of the reference drugs benznidazole and miltefosine. Due to these promising results, we set out to explore the impact of structural modifications on the bioactivity of this natural product. In order to generate aurachin D derivatives with varying substituents at the C-2, C-6 and C-7 position of the quinolone ring system, we resorted to whole-cell biotransformation using a recombinant Escherichia coli strain capable of aurachin-type prenylations. Quinolone precursor molecules featuring methyl, methoxy and halogen groups were fed to this E. coli strain, which converted the substrates into the desired analogs. None of the generated derivatives exhibited improved antiprotozoal properties in comparison to aurachin D. Obviously, the naturally occurring aurachin D features already a privileged structure, especially for the inhibition of the causative agent of visceral leishmaniasis. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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19 pages, 2435 KiB

Open AccessArticle

New Benzofuran Oligomers from the Roots of Eupatorium heterophyllum Collected in China

by Yiming Hu, Yoshinori Saito, Yosuke Matsuo, Xun Gong and Takashi Tanaka

Molecules 2022, 27(24), 8856; https://doi.org/10.3390/molecules27248856 - 13 Dec 2022

Cited by 2 | Viewed by 1207

Abstract

The chemical constituents of two root samples of Eupatorium heterophyllum DC. collected in Yunnan Province, China, were investigated. Five new oligomeric benzofurans (1–5), nine new benzofuran/dihydrobenzofuran derivatives, and a new thymol analog were isolated, and their structures were determined [...] Read more.

The chemical constituents of two root samples of Eupatorium heterophyllum DC. collected in Yunnan Province, China, were investigated. Five new oligomeric benzofurans (1–5), nine new benzofuran/dihydrobenzofuran derivatives, and a new thymol analog were isolated, and their structures were determined using extensive spectroscopic techniques, such as 1D and 2D NMR spectroscopy and DFT calculations of the CD spectra. Most of the new compounds, including oligomeric benzofurans (1–5), were obtained from only one of the root samples. Furthermore, this is the first example that produces oligomeric benzofurans in this plant. These results imply that diversification of secondary metabolites in E. heterophyllum is ongoing. Plausible biosynthetic pathways for 1–5 are also proposed. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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13 pages, 2598 KiB

Open AccessArticle

Characterization of Conyza bonariensis Allelochemicals against Broomrape Weeds

by Antonio Cala Peralta, Gabriele Soriano, Jesús G. Zorrilla, Marco Masi, Alessio Cimmino and Mónica Fernández-Aparicio

Molecules 2022, 27(21), 7421; https://doi.org/10.3390/molecules27217421 - 01 Nov 2022

Cited by 5 | Viewed by 1718

Abstract

The study of allelopathic activity of plants and the isolation and characterization of the responsible allelochemicals can lead to the development of environment friendly alternative approaches to weed control. Conyza species are invasive weeds that use allelopathic activity as part of a successful [...] Read more.

The study of allelopathic activity of plants and the isolation and characterization of the responsible allelochemicals can lead to the development of environment friendly alternative approaches to weed control. Conyza species are invasive weeds that use allelopathic activity as part of a successful strategy to outcompete neighboring plants. Broomrape weeds are parasitic plants that use host-induced germination and the formation of a haustorium as strategies to infect host plants. The control of broomrape infection in most affected crops is limited or non-existing. In the current study, we investigated the allelopathic activity of Conyza bonariensis organic extracts in suicidal germination and radicle growth of four broomrape species (Orobanche crenata, Orobanche cumana, Orobanche minor and Phelipanche ramosa). A bioactivity-driven fractionation of Conyza bonariensis extracts led to the identification of two germination-inducing molecules and two growth-inhibitory compounds. The germination-inducing metabolites had species-specific activity being hispidulin active on seeds of O. cumana and methyl 4-hydroxybenzoate active in P. ramosa. The growth-inhibitory metabolites (4Z)-lachnophyllum lactone and (4Z,8Z)-matricaria lactone strongly inhibited the radicle growth of all parasitic weed species studied. Some structure–activity relationships were found as result of the study herein presented. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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20 pages, 4679 KiB

Open AccessArticle

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (Pr³⁺, Eu³⁺, Ho³⁺, Tm³⁺)

by Maria Michela Salvatore, Antonietta Siciliano, Alessia Staropoli, Francesco Vinale, Rosario Nicoletti, Marina DellaGreca, Marco Guida, Francesco Salvatore, Mauro Iuliano, Anna Andolfi and Gaetano De Tommaso

Molecules 2022, 27(19), 6468; https://doi.org/10.3390/molecules27196468 - 01 Oct 2022

Cited by 2 | Viewed by 1385

Abstract

Rare-earth elements (REEs) are in all respect a class of new contaminants that may have toxic effects on organisms and microorganisms and information on their interactions with natural ligands should be of value to predict and control their diffusion in natural environments. In [...] Read more.

Rare-earth elements (REEs) are in all respect a class of new contaminants that may have toxic effects on organisms and microorganisms and information on their interactions with natural ligands should be of value to predict and control their diffusion in natural environments. In the current study, we investigate interactions of tripositive cations of praseodymium, europium, holmium, and thulium with harzianic acid (H₂L), a secondary metabolite produced by selected strains of fungi belonging to the Trichoderma genus. We applied the same techniques and workflow previously employed in an analogous study concerning lanthanum, neodymium, samarium, and gadolinium tripositive cations. Therefore, in the current study, HPLC-ESI-HRMS experiments, circular dichroism (CD), and UV-Vis spectrophotometric absorption data, as well as accurate pH measurements, were applied to characterize bonding interactions between harzianic acid and Pr³⁺, Eu³⁺, Ho³⁺, and Tm³⁺ cations. Problems connected to the low solubility of harzianic acid in water were overcome by employing a 0.1 M NaClO₄/(CH₃OH + H₂O 50/50 w/w) mixed solvent. For Pr³⁺, Ho³⁺, and Tm³⁺, only the mono complexes PrL⁺, HoL⁺, and TmL⁺ were detected and their formation constant determined. Eu³⁺ forms almost exclusively the bis complex

{EuL}_{2}^{-}

for which the corresponding formation constant is reported; under our experimental conditions, the mono complex EuL⁺ is irrelevant. Combining the results of the present and previous studies, a picture of interactions of harzianic acid with rare-earth cations extending over 8 of the 17 REEs can be composed. In order to complement chemical information with toxicological information, a battery of bioassays was applied to evaluate the effects of praseodymium, europium, holmium, and thulium tripositive cations on a suite of bioindicators including Aliivibrio fischeri (Gram-negative bacterium), Raphidocelis subcapitata (green alga), and Daphnia magna (microcrustacean), and median effective concentration (EC50) values of Pr³⁺, Eu³⁺, Ho³⁺, and Tm³⁺ for the tested species were assessed. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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12 pages, 1732 KiB

Open AccessArticle

New 11-Methoxymethylgermacranolides from the Whole Plant of Carpesium divaricatum

by Tao Zhang, Haixin Zhang, Chunyu Lin, Lu Fu and Zhongmei Zou

Molecules 2022, 27(18), 5991; https://doi.org/10.3390/molecules27185991 - 14 Sep 2022

Viewed by 1081

Abstract

Eight new 11-methoxymethylgermacranolides (1–8) were isolated from the ethanol extract of the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by detailed spectroscopic analysis. The absolute configuration of 1 [...] Read more.

Eight new 11-methoxymethylgermacranolides (1–8) were isolated from the ethanol extract of the whole plant of Carpesium divaricatum. The planar structures and relative configurations of the new compounds were determined by detailed spectroscopic analysis. The absolute configuration of 1 was established by electronic circular dichroism (ECD) spectrum and X-ray crystallographic analysis, and the stereochemistry of the new compounds 2–8 were determined by similar ECD data with 1. The absolute configurations of 5 and 7 were further confirmed by using quantum chemical electronic circular dichroism (ECD) calculations. Compound 4 exhibited weak cytotoxicity against MCF-7 cells. Compound 8 could potently decrease PGE2 productions in LPS-induced RAW 264.7 cells. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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12 pages, 984 KiB

Open AccessArticle

Trichoderma Enzymes for Degradation of Aflatoxin B1 and Ochratoxin A

by Irene Dini, Vittoria Alborino, Stefania Lanzuise, Nadia Lombardi, Roberta Marra, Anna Balestrieri, Alberto Ritieni, Sheridan L. Woo and Francesco Vinale

Molecules 2022, 27(12), 3959; https://doi.org/10.3390/molecules27123959 - 20 Jun 2022

Cited by 14 | Viewed by 2262

Abstract

The contamination of agricultural products with mycotoxins causes risks to animal and human health and severe economic losses. Mycotoxicoses can be reduced by preventing fungal infection using chemical and biological approaches. The chemical strategies can release toxic molecules; therefore, strategies for biological control [...] Read more.

The contamination of agricultural products with mycotoxins causes risks to animal and human health and severe economic losses. Mycotoxicoses can be reduced by preventing fungal infection using chemical and biological approaches. The chemical strategies can release toxic molecules; therefore, strategies for biological control are being evaluated, such as using nontoxic fungi and their metabolites. This work evaluated the effect of exoenzymes produced by the beneficial fungus Trichoderma afroharzianum strain T22 in degrading Aflatoxin B1 (AFB1) and Ochratoxin A (OTA). The ability of Trichoderma to produce hydrolases was stimulated by using different inducing substrates. The highest AFB1 and OTA degradation activity was obtained using a medium containing lyophilized mushrooms and crude fiber. The T. afroharzianum T22’s ability to reduce mycotoxins may be attributed to peroxidase enzymes. This study showed that T.afroharzianum strain T22 or its peroxidase supplementation could represent a sustainable strategy for the degradation of AFB1 and OTA in feed and food products. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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17 pages, 3400 KiB

Open AccessArticle

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (La³⁺, Nd³⁺, Sm³⁺, Gd³⁺)

by Gaetano De Tommaso, Maria Michela Salvatore, Antonietta Siciliano, Alessia Staropoli, Francesco Vinale, Rosario Nicoletti, Marina DellaGreca, Marco Guida, Francesco Salvatore, Mauro Iuliano and Anna Andolfi

Molecules 2022, 27(6), 1959; https://doi.org/10.3390/molecules27061959 - 17 Mar 2022

Cited by 3 | Viewed by 1741

Abstract

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H₂L), [...] Read more.

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H₂L), a Trichoderma secondary metabolite, of a selection of tripositive rare-earth cations Ln³⁺ (Ln³⁺ = La³⁺, Nd³⁺, Sm^3+, and Gd³⁺) was investigated at 25 °C, and in a CH₃OH/0.1 M NaClO₄ (50/50 w/w) solvent, using mass spectrometry, circular dichroism, UV–Vis spectrophotometry, and pH measurements. Experimental data can be satisfactorily explained by assuming, for all investigated cations, the formation of a mono-complex (LnL⁺) and a bis-complex (LnL₂⁻). Differences were found between the formation constants of complexes of different Ln³⁺ cations, which can be correlated with ionic radius. Since gadolinium is the element that raises the most concern among lanthanide elements, its effects on organisms at different levels of biological organization were explored, in the presence and absence of harzianic acid. Results of ecotoxicological tests suggest that harzianic acid can decrease gadolinium biotoxicity, presumably because of complex formation with Gd³⁺. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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14 pages, 2332 KiB

Open AccessArticle

Isolation of a Novel Polyketide from Neodidymelliopsis sp.

by Melissa M. Cadelis, Hugo Gordon, Alex Grey, Soeren Geese, Daniel R. Mulholland, Bevan S. Weir, Brent R. Copp and Siouxsie Wiles

Molecules 2021, 26(11), 3235; https://doi.org/10.3390/molecules26113235 - 27 May 2021

Cited by 7 | Viewed by 3506

Abstract

Fungi have become an invaluable source of bioactive natural products, with more than 5 million species of fungi spanning the globe. Fractionation of crude extract of Neodidymelliopsis sp., led to the isolation of a novel polyketide, (2Z)-cillifuranone (1) and [...] Read more.

Fungi have become an invaluable source of bioactive natural products, with more than 5 million species of fungi spanning the globe. Fractionation of crude extract of Neodidymelliopsis sp., led to the isolation of a novel polyketide, (2Z)-cillifuranone (1) and five previously reported natural products, (2E)-cillifuranone (2), taiwapyrone (3), xylariolide D (4), pachybasin (5), and N-(5-hydroxypentyl)acetamide (6). It was discovered that (2Z)-cillifuranone (1) was particularly sensitive to ambient temperature and light resulting in isomerisation to (2E)-cillifuranone (2). Structure elucidation of all the natural products were conducted by NMR spectroscopic techniques. The antimicrobial activity of 2, 3, and 5 were evaluated against a variety of bacterial and fungal pathogens. A sodium [1-¹³C] acetate labelling study was conducted on Neodidymelliopsis sp. and confirmed that pachybasin is biosynthesised through the acetate polyketide pathway. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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15 pages, 1519 KiB

Open AccessArticle

Changes in Human Erythrocyte Membrane Exposed to Aqueous and Ethanolic Extracts from Uncaria tomentosa

by Piotr Duchnowicz, Radosław Pilarski, Jaromir Michałowicz and Bożena Bukowska

Molecules 2021, 26(11), 3189; https://doi.org/10.3390/molecules26113189 - 26 May 2021

Cited by 7 | Viewed by 2437

Abstract

Uncaria tomentosa (Willd.) DC is a woody climber species originating from South and Central America that has been used in the therapy of asthma, rheumatism, hypertension, and blood purification. Our previous study showed that U. tomentosa extracts altered human erythrocyte shape, which could [...] Read more.

Uncaria tomentosa (Willd.) DC is a woody climber species originating from South and Central America that has been used in the therapy of asthma, rheumatism, hypertension, and blood purification. Our previous study showed that U. tomentosa extracts altered human erythrocyte shape, which could be due to incorporation of the compounds contained in extracts into the erythrocyte membrane. The aim of the present study was to determine how the compounds contained in U. tomentosa extracts incorporate into the human erythrocyte membrane. The study has assessed the effect of aqueous and ethanolic extracts from leaves and bark of U. tomentosa on the osmotic resistance of the human erythrocyte, the viscosity of erythrocyte interior, and the fluidity of erythrocyte plasma membrane. Human erythrocytes were incubated with the studied extracts in the concentrations of 100, 250, and 500 µg/mL for 2, 5, and 24 h. All extracts tested caused a decrease in erythrocyte membrane fluidity and increased erythrocyte osmotic sensitivity. The ethanolic extracts from the bark and leaves increased viscosity of the erythrocytes. The largest changes in the studied parameters were observed in the cells incubated with bark ethanolic extract. We consider that the compounds from U. tomentosa extracts mainly build into the outer, hydrophilic monolayer of the erythrocyte membrane, thus protecting the erythrocytes against the adverse effects of oxidative stress. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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18 pages, 1352 KiB

Open AccessArticle

Effect of Salt Stress on Growth and Metabolite Profiles of Cape Gooseberry (Physalis peruviana L.) along Three Growth Stages

by Daissy Monroy-Velandia and Ericsson Coy-Barrera

Molecules 2021, 26(9), 2756; https://doi.org/10.3390/molecules26092756 - 07 May 2021

Cited by 6 | Viewed by 2482

Abstract

Colombia is the main producer of cape gooseberry (Physalis peruviana L.), a plant known for its various consumption practices and medicinal properties. This plant is generally grown in eroded soils and is considered moderately tolerant to unfavorable conditions, such as nutrient-poor soils [...] Read more.

Colombia is the main producer of cape gooseberry (Physalis peruviana L.), a plant known for its various consumption practices and medicinal properties. This plant is generally grown in eroded soils and is considered moderately tolerant to unfavorable conditions, such as nutrient-poor soils or high salt concentrations. Most studies conducted on this plant focus on fruit production and composition because it is the target product, but a small number of studies have been conducted to describe the effect of abiotic stress, e.g., salt stress, on growth and biochemical responses. In order to better understand the mechanism of inherent tolerance of this plant facing salt stress, the present study was conducted to determine the metabolic and growth differences of P. peruviana plants at three different BBCH-based growth substages, varying salt conditions. Hence, plants were independently treated with two NaCl solutions, and growth parameters and LC-ESI-MS-derived semi-quantitative levels of metabolites were then measured and compared between salt treatments per growth substage. A 90 mM NaCl treatment caused the greatest effect on plants, provoking low growth and particular metabolite variations. The treatment discrimination-driving feature classification suggested that glycosylated flavonols increased under 30 mM NaCl at 209 substages, withanolides decreased under 90 mM NaCl at 603 and 703 substages, and up-regulation of a free flavonol at all selected stages can be considered a salt stress response. Findings locate such response into a metabolic context and afford some insights into the plant response associated with antioxidant compound up-regulation. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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Review

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27 pages, 760 KiB

Open AccessReview

A Concise Profile of Gallic Acid—From Its Natural Sources through Biological Properties and Chemical Methods of Determination

by Dorota Wianowska and Małgorzata Olszowy-Tomczyk

Molecules 2023, 28(3), 1186; https://doi.org/10.3390/molecules28031186 - 25 Jan 2023

Cited by 12 | Viewed by 2926

Abstract

Nature is a valuable source of anti-oxidants that have a health-promoting effect by inhibiting various undesirable changes leading to cell degradation and, consequently, potential disease ailments. One of them is gallic acid which has been used as a healing agent since ancient times. [...] Read more.

Nature is a valuable source of anti-oxidants that have a health-promoting effect by inhibiting various undesirable changes leading to cell degradation and, consequently, potential disease ailments. One of them is gallic acid which has been used as a healing agent since ancient times. Currently, due to various beneficial properties, this compound is considered to be one of the main phenolic acids of great importance in numerous industries. It is commonly used as a substance protecting against the harmful effects of UV radiation, an astringent in cosmetic preparations, and a preservative in food products. Therefore, gallic acid is now deemed essential for both human health and industry. Increasingly better methods of its isolation and analysis are being developed, and new solutions are being sought to increase its production. This review, presenting a concise characterization of gallic acid, updates the knowledge about its various biological activities and methods used for its isolation and determination, including chromatographic and non-chromatographic methods. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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45 pages, 10006 KiB

Open AccessReview

The Genus Cladosporium: A Rich Source of Diverse and Bioactive Natural Compounds

by Maria Michela Salvatore, Anna Andolfi and Rosario Nicoletti

Molecules 2021, 26(13), 3959; https://doi.org/10.3390/molecules26133959 - 28 Jun 2021

Cited by 42 | Viewed by 4147

Abstract

Fungi are renowned as one of the most fruitful sources of chemodiversity and for their ubiquitous occurrence. Among the many taxonomic groupings considered for the implications deriving from their biosynthetic aptitudes, the genus Cladosporium stands out as one of the most common in [...] Read more.

Fungi are renowned as one of the most fruitful sources of chemodiversity and for their ubiquitous occurrence. Among the many taxonomic groupings considered for the implications deriving from their biosynthetic aptitudes, the genus Cladosporium stands out as one of the most common in indoor environments. A better understanding of the impact of these fungi on human health and activities is clearly based on the improvement of our knowledge of the structural aspects and biological properties of their secondary metabolites, which are reviewed in the present paper. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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42 pages, 440 KiB

Open AccessReview

Secondary Metabolites from Artemisia Genus as Biopesticides and Innovative Nano-Based Application Strategies

by Bianca Ivănescu, Ana Flavia Burlec, Florina Crivoi, Crăița Roșu and Andreia Corciovă

Molecules 2021, 26(10), 3061; https://doi.org/10.3390/molecules26103061 - 20 May 2021

Cited by 36 | Viewed by 5424

Abstract

The Artemisia genus includes a large number of species with worldwide distribution and diverse chemical composition. The secondary metabolites of Artemisia species have numerous applications in the health, cosmetics, and food sectors. Moreover, many compounds of this genus are known for their antimicrobial, [...] Read more.

The Artemisia genus includes a large number of species with worldwide distribution and diverse chemical composition. The secondary metabolites of Artemisia species have numerous applications in the health, cosmetics, and food sectors. Moreover, many compounds of this genus are known for their antimicrobial, insecticidal, parasiticidal, and phytotoxic properties, which recommend them as possible biological control agents against plant pests. This paper aims to evaluate the latest available information related to the pesticidal properties of Artemisia compounds and extracts and their potential use in crop protection. Another aspect discussed in this review is the use of nanotechnology as a valuable trend for obtaining pesticides. Nanoparticles, nanoemulsions, and nanocapsules represent a more efficient method of biopesticide delivery with increased stability and potency, reduced toxicity, and extended duration of action. Given the negative impact of synthetic pesticides on human health and on the environment, Artemisia-derived biopesticides and their nanoformulations emerge as promising ecofriendly alternatives to pest management. Full article

(This article belongs to the Special Issue Natural Secondary Metabolites II)

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