Multitarget anti-parasitic activities of isoquinoline alkaloids isolated from Hippeastrum aulicum (Amaryllidaceae)

BACKGROUND

Chagas disease and leishmaniasis affect a significant portion of the Latin American population and still lack efficient treatments. In this context, natural products emerge as promising compounds for developing more effective therapies, aiming to mitigate side effects and drug resistance. Notably, species from the Amaryllidaceae family emerge as potential reservoirs of antiparasitic agents due to the presence of diverse biologically active alkaloids.

PURPOSE

To assess the anti-Trypanosoma cruzi and anti-Leishmania infantum activity of five isolated alkaloids from Hippeastrum aulicum Herb. (Amaryllidaceae) against different life stages of the parasites using in silico and in vitro assays. Furthermore, molecular docking was employed to evaluate the interaction of the most active alkaloids.

METHODS

Five natural isoquinoline alkaloids isolated in suitable quantities for in vitro testing underwent preliminary in silico analysis to predict their potential efficacy against Trypanosoma cruzi (amastigote and trypomastigote forms) and Leishmania infantum (amastigote and promastigote forms). The in vitro antiparasitic activity and mammalian cytotoxicity were investigated with a subsequent comparison of both analysis (in silico and in vitro) findings. Additionally, this study employed the molecular docking technique, utilizing cruzain (T. cruzi) and sterol 14α-demethylase (CYP51, L. infantum) as crucial biological targets for parasite survival, specifically focusing on compounds that exhibited promising activities against both parasites.

RESULTS

Through computational techniques, it was identified that the alkaloids haemanthamine (1) and lycorine (8) were the most active against T. cruzi (amastigote and trypomastigote) and L. infantum (amastigote and promastigote), while also revealing unprecedented activity of alkaloid 7‑methoxy-O-methyllycorenine (6). The in vitro analysis confirmed the in silico tests, in which compound 1 presented the best activities against the promastigote and amastigote forms of L. infantum with half-maximal inhibitory concentration (IC50) 0.6 µM and 1.78 µM, respectively. Compound 8 exhibited significant activity against the amastigote form of T. cruzi (IC50 7.70 µM), and compound 6 demonstrated activity against the trypomastigote forms of T. cruzi and amastigote of L. infantum, with IC50 values of 89.55 and 86.12 µM, respectively. Molecular docking analyses indicated that alkaloids 1 and 8 exhibited superior interaction energies compared to the inhibitors.

CONCLUSION

The hitherto unreported potential of compound 6 against T. cruzi trypomastigotes and L. infantum amastigotes is now brought to the forefront. Furthermore, the acquired dataset signifies that the isolated alkaloids 1 and 8 from H. aulicum might serve as prototypes for subsequent structural refinements aimed at the exploration of novel leads against both T. cruzi and L. infantum parasites.

The Anti-Cholinesterase Potential of Fifteen Different Species of Narcissus L. (Amaryllidaceae) Collected in Spain

Narcissus L. is a renowned plant genus with a notable center of diversity and is primarily located in the Mediterranean region. These plants are widely recognized for their ornamental value, owing to the beauty of their flowers; nonetheless, they also hold pharmacological importance. In Europe, pharmaceutical companies usually use the bulbs of Narcissus pseudonarcissus cv. Carlton to extract galanthamine, which is one of the few medications approved by the FDA for the palliative treatment of mild-to-moderate symptoms of Alzheimer's disease. The purpose of this study was to evaluate the potential of these plants in Alzheimer's disease. The alkaloid extract from the leaves of different species of Narcissus was obtained by an acid-base extraction work-up -procedure. The biological potential of the samples was carried out by evaluating their ability to inhibit the enzymes acetyl- and butyrylcholinesterase (AChE and BuChE, respectively). The species N. jacetanus exhibited the best inhibition values against AChE, with IC50 values of 0.75 ± 0.03 µg·mL-1, while N. jonquilla was the most active against BuChE, with IC50 values of 11.72 ± 1.15 µg·mL-1.

Ligand fishing approach to explore Amaryllidaceae alkaloids as potential antiviral candidates targeting SARS-CoV-2 Nsp4

Ligand fishing, also described as affinity-based assay, represents a convenient and efficient approach to separate potential ligands from complex matrixes or chemical libraries. This approach contributes to the identification of lead compounds that can bind to a specific target. In the context of COVID-19, the search for novel therapeutic agents is crucial. Small molecule-based antiviral drugs, such as Amaryllidaceae alkaloids, have been described as potential candidates because they can inhibit RNA viruses. Among various SARS-CoV-2 proteins, Nsp3, Nsp4, and Nsp6 play a crucial role in the pathogenicity of the virus and are attractive targets for developing COVID-19 treatments. These proteins are responsible for the replication/transcription complex (RTC) within double-membrane vesicles (DMVs), and their inhibition disrupts the virus's infectious cycle. Herein, we have successfully expressed and immobilized the SARS-CoV-2 Nsp4 protein on magnetic beads (Nsp4-MBs) and employed a ligand fishing assay to screen a collection of ten Amaryllidaceae-based alkaloids and applied to Hippeastrum aulicum extract. Remarkably, four out of ten alkaloids, namely 2-α-7-dimethoxyhomolycorine (6), haemanthamine (5), albomaculine (8), and tazettine (9), exhibited selective affinities for Nsp4. Albomaculine (8) and haemanthamine (5) were also identified from extract by the affinity assay. These findings highlight the potential of these alkaloids as model compounds for future drug discovery studies aimed at developing therapeutic interventions against SARS-CoV-2 infections.

Anti-Candida, docking studies, and in vitro metabolism-mediated cytotoxicity evaluation of Eugenol derivatives

The high morbidity and mortality rates of Candida infections, especially among immunocompromised patients, are related to the increased resistance rate of these species and the limited therapeutic arsenal. In this context, we evaluated the anti-Candida potential and the cytotoxic profile of eugenol derivatives. Anti-Candida activity was evaluated on C. albicans and C. parapsilosis strains by minimum inhibitory concentration (MIC), scanning electron microscopy (SEM), and molecular docking calculations at the site of the enzyme lanosterol-14-α-demethylase active site, responsible for ergosterol formation. The cytotoxic profile was evaluated in HepG2 cells, in the presence and absence of the metabolizing system (S9 system). The results indicated compounds 1b and 1d as the most active ones. The compounds have anti-Candida activity against both strains with MIC ranging from 50 to 100 μg ml^-1 . SEM analyses of 1b and 1d indicated changes in the envelope architecture of both C. albicans and C. parapsilosis like the ones of eugenol and fluconazole, respectively. Docking results of the evaluated compounds indicated a similar binding pattern of fluconazole and posaconazole at the lanosterol-14-α-demethylase binding site. In the presence of the S9 system, compound 1b showed the same cytotoxicity profile as fluconazole (1.08 times) and compound 1d had 1.23 times increase in cytotoxicity. Eugenol and other evaluated compounds showed a significant increase in cytotoxicity. Our results suggest compound 1b as a promising starting point candidate to be used in the design of new anti-Candida agent prototypes.

Synthesis and Phytotoxic Evaluation of Isatin Derivatives Supported by 3D-QSAR Study

Concerned about weed infestation, a major threat to food production and herbicide resistance that interferes in the mechanism of action of the main herbicides, we have synthesized eight isatin derivatives using the "Click Chemistry" approach through copper-catalyzed azide-alkyne cycloadditions (CuAAC). Sixteen isatin derivatives were evaluated for their phytotoxic activity against the seed culture of the model plants, Lactuca sativa and Allium cepa. Six of them showed phytotoxic activity similar to the positive control, trifluralin. Hypocotyl length measurement analysis in L. sativa revealed that triazole derivative 8 is more active than trifluralin. For A. cepa, root length measurement analyses revealed that 3, 10, 14, 16, and 17 were similar to the positive control trifluralin. Three-dimensional quantitative structure-activity relationship (3D-QSAR) comparative molecular field analysis (CoMFA) model construction using the acetolactate synthase (ALS) crystallographic structure displayed pk_i values of predicted inhibitory activity and contour maps revealing sterically bulky groups for 11, the CF₃ group in ortho, and for 17, Br in ortho, favoring the inhibitory ALS activity.

(R)-(+)-Lasiodiplodin isolated from the endophytic fungus Sordaria tamaensis exhibits potent antimycobacterial and anti-inflammatory activities in vitro and in vivo: a dual approach for the treatment of severe pulmonary tuberculosis

OBJECTIVES

This study aimed to evaluate endophytic fungi isolated from Tocoyena bullata and Humiria balsamifera plant species for their antimycobacterial and anti-inflammatory activities, focusing on severe pulmonary tuberculosis cases which are often associated with exacerbated inflammation.

METHODS

Mycobacterium suspensions were incubated with the samples for 5 days. RAW 264.7 macrophages stimulated with LPS were also incubated with them for 24 h to assess the inhibition of inflammatory mediator production and cytotoxicity. C57BL/6 mice were infected with Mtb M299 and treated for 15 days with lasiodiplodin (Lasio).

KEY FINDINGS

Endophytic fungus Sordaria tamaensis, obtained from T. bullata, was the most promising. Its ethanolic extract impaired mycobacterial growth with MIC50 (µg/ml): 1.5 ± 0.6 (BCG), 66.8 ± 0.1 (H37Rv) and 80.0 ± 0.1 (M299). (R)-(+)-Lasio showed MIC50 92.2 ± 1.8 µg/ml (M299). In addition, Lasio was able to inhibit NO, IL-1β and TNF-α production and was not cytotoxic for macrophages. M. tuberculosis-infected C57BL/6 animals treated by Lasio reduced the number of acid-fast bacilli, lung pathology, leucocyte influx and proinflammatory cytokine production in the lungs. The class IIa fructose 1,6-bisphosphate aldolase was the predicted hypothetical target of Lasio.

CONCLUSIONS

(R)-(+)-Lasio stood out as a promising anti-TB compound, exhibiting anti-inflammatory and antimycobacterial effects, as well as low cytotoxicity.

Thymol as an Interesting Building Block for Promising Fungicides against Fusarium solani

The semisynthesis of 15 new thymol derivatives was achieved through Williamson synthesis and copper-catalyzed azide-alkyne cycloaddition (CuAAC) approaches. The reaction of CuAAC using the "Click Chemistry" strategy, in the presence of an alkynyl thymol derivative and commercial or prepared azides, provided nine thymol derivatives under microwave irradiation. This procedure reduces reaction time and cost. All molecular entities were elucidated by ¹H and ¹³C NMR, IR, and HRMS data. These derivatives were evaluated in vitro for their fungicidal activity against Fusarium solani sp. Among the nine triazolic thymol derivatives obtained, seven of them were found to have moderated antifungal activity. In contrast, naphthoquinone/thymol hybrid ether 2b displayed activity comparable with that of the commercial fungicide thiabendazole. The structure-activity relationship for the most active compound 2b was discussed, and the mode of action was predicted by a possible binding to the fungic ergosterol and interference of osmotic balance of K⁺ into the extracellular medium.

Mesoporous molecularly imprinted polymer core@shell hybrid silica nanoparticles as adsorbent in microextraction by packed sorbent for multiresidue determination of pesticides in apple juice

In this work, we report the synthesis of a mesoporous molecularly imprinted polymer on the surface of silica nanoparticles (core@mMIP) to be applied as adsorbent in microextraction by packed sorbent (MEPS) for selective determination of pesticides in apple juice. The core@mMIP was properly characterized, showing good adhesion of the polymer to the silica core. The best extraction conditions were: 200 µL of ultrapure water as washing solvent, 150 µL of acetonitrile as eluent, 100 µL of sample at pH 2.5, five draw-eject cycles and 8 mg of adsorbent. Thereby, recoveries of 96.12 ± 1.05%, 76.88 ± 6.18% and 76.18 ± 5.57% were obtained for pyriproxyfen (PPX), deltamethrin (DTM) and etofenprox (ETF), respectively. After validation, the method presented linearity in the range of 0.02-10 µg mL^-1 (r > 0.99), limit of detection of 0.005 µg mL^-1, satisfactory selectivity, and proper precision and accuracy. The method was successfully applied real samples of processed and fresh apple juice.

Acetylcholinesterase inhibitory activity, anti-inflammatory, and neuroprotective potential of Hippeastrum psittacinum (Ker Gawl.) herb (Amaryllidaceae)

Hippeastrum psittacinum, Amaryllidaceae, is used in traditional medicine as a purgative, aphrodisiac, and anticough remedy. The ethanol extract (EE) and alkaloid-rich fractions (ARF) from H. psittacinum bulbs were evaluated for their acetylcholinesterase (AChE) inhibition. The EE cytotoxic and anti-inflammatory effects in RAW 264.7 cells, and the neuroprotective and genotoxic activities in SH-SY5Y cells, were also estimated. Fifteen alkaloids were identified in the EE by gas chromatography-mass spectrometry. ARFs were less active for AChE inhibition than EE. The viability of both cell lines was higher than 70% with EE concentrations below 25 μg/mL. The EE decreased nitrite release in RAW cells stimulated with lipopolysaccharide, showing values of 83, 67, and 53% at 6.25, 12.5, and 25 μg/mL, respectively. Furthermore, the EE partially protected SH-SY5Y cells from hydrogen peroxide-mediated deleterious effects by approximately 50% at the same concentrations. The micronucleus assays showed that the extract caused chromosomal missegregation at concentrations above 12.5 μg/mL. The in silico analyses showed that some alkaloids presented properties of permeation of the blood-brain barrier and the intestine. Our findings present new evidence of the potential of H. psittacinum potential as an AChE inhibitor, as well as an anti-inflammatory and neuroprotective agent.

Tucumã (Astrocaryum aculeatum) extract: phytochemical characterization, acute and subacute oral toxicity studies in Wistar rats

Natural products are often used by the population to treat and/or prevent several disorders. Tucumã is an Amazonian fruit widely consumed by local population and no in vivo toxicity studies regarding its safety are available in the literature to date. Therefore, the phytochemical characterization, acute and repeated dose 28-day oral toxicities of crude extract of tucumã's pulp (CETP) in Wistar rats were evaluated. For the CETP preparation, tucumã pulp was crushed and placed into sealed amber glass jars containing absolute ethanol solution for extraction. CETP phytochemical analyses evidenced the presence of carotenoids, flavonoids, unsaturated and satured fatty acids, and triterpenes. In the acute toxicity, female rats from the test group were treated with CETP at single dose of 2000 mg/kg. For the repeated dose toxicity, CETP was administered to male and female rats at doses of 200, 400 and 600 mg/kg, for 28 days. Body weight was recorded during the experiment and blood, liver and kidney were collected for further analysis. No mortality or toxicity signs were observed during the studies. CETP was classified as safe (category 5, OECD guide), in acute toxicity. In repeated dose study was observed alterations in some biochemical parameters, as well as in oxidative damage and enzymatic activity. Histopathological findings showed renal damage in male rats at higher dose. The data obtained suggest that CETP did not induced toxicity after exposure to a single or repeated doses in female rats. However, in males may be considered safe when given repeatedly in low doses.

Novel [6]-gingerol Triazole Derivatives and their Antiproliferative Potential against Tumor Cells

BACKGROUND

Effective cancer treatment is a major public health challenge. The limitations of current therapies and their adverse effects reduce the efficacy of treatment, leading to significant mortality rates worldwide. Moreover, natural product chemistry occupies a prominent role in the search for new treatment alternatives, by contributing a spectrum of chemical structures that may potentially yield new bioactive compounds. The compound [6]-gingerol (1) is the main active substance in ginger (Zingiber officinale) and several studies have shown it to produce beneficial effects, including antitumor activity.

OBJECTIVE

This work aims to obtain new gingerol derivatives with cytotoxic activity.

METHODS

[6]-gingerol was isolated and its derivatives were produced using click chemistry, obtaining eight new compounds. All chemical structures were determined by means of IR, NMR and HRMS data, and cytotoxicity was evaluated in the HCT 116 (colon carcinoma) and MCF-7 (breast carcinoma) cell lines at concentrations of 5 µmol L-1 and 50 µmol L-1.

RESULTS

At 50 µmol L-1, more than 70% inhibition of cell growth was achieved with compounds 2e, 2g against HCT 116, and 2b, 2d, 2e, 2f and 2g against MCF-7.

CONCLUSION

The obtained compounds showed only moderate cytotoxic activity. However, the products with substituents occupying the meta position in relation to the triazole ring showed increased cytotoxic properties. The brominated compound (2g) showed the strongest activity, inhibiting cell proliferation by 87%.

Isoquinoline alkaloids reduce beta-amyloid peptide toxicity in Caenorhabditis elegans

Alzheimer's disease (AD) is a multifactorial health problem widespread over the world. Regarding the historical importance of the alkaloids in the central nervous system pharmacology they remain as promising drug candidates against AD. Seven alkaloids from Amaryllidaceae and Fabaceae were evaluated in vivo, in vitro and in silico targets related to the AD pathophysiology. Erythraline and erysodine showed the greatest potential compared to Memantine, a drug currently used in AD therapy, by delaying the Aβ_1-42-induced paralysis in the transgenic strain CL2006 Caenorhabditis elegans, an alternative model to assess the impairment of beta-amyloid peptide deposition. The in vitro inhibition of the acetylcholinesterase was observed for the first time for Erythrina alkaloids; however Lycorine was the most active. Docking simulation contributed to comprehend this potential by showing a hydrophobic interaction between acetylcholinesterase and Lycorine in the amino acid residue TRP 84 as well as hydrogen bonds with TRY 121 and ASP 72.

Profiling of acetylcholinesterase inhibitory alkaloids from some Crinum, Habranthus and Zephyranthes species by GC-MS combined with multivariate analyses and in silico studies

Acetylcholinesterase (AChE) inhibitors remain the class of drugs used for the treatment of Alzheimer disease (AD). For the aim of discovering new sources of potent AChE inhibitors, a combined AChE-inhibitory activity together with alkaloid profiles by GC-MS, combined with multivariate statistical analysis for biomarkers determination and in silico studies were attempted. Strategy was applied on leaves, roots and bulbs of six aquatic and terrestrial Amaryllidaceae species. Thirty alkaloids were identified and the AChE inhibitory activities of the extracts were tested by in-vitro Ellman method. Principal bioactive markers were discovered by correlating AChE inhibitory activity with chemical fingerprints via PLS and OPLS modeling which revealed that galanthamine, lycoramine, caranine, tazettine and N-demethylgalanthamine were the most bio-significant markers. Furthermore, the molecular docking was performed to illustrate binding orientations of the top scoring alkaloids in the active site of human acetylcholinesterase. Suggested strategy revealed that, beside galanthamine, caranine, N-demethylgalanthamine, and lycoramine are promising AChE inhibitors.

Evaluation of physicochemical properties as supporting information on quality control of raw materials and veterinary pharmaceutical formulations

This study aimed to show that the physicochemical proprieties obtained by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and scanning electronic microscopy (SEM) can be useful tools for evaluating the quality of active pharmaceutical ingredients (APIs) and pharmaceutical products. In addition, a simple, sensitive, and efficient method employing HPLC-DAD was developed for simultaneous determination of lidocaine (LID), ciprofloxacin (CFX) and enrofloxacin (EFX) in raw materials and in veterinary pharmaceutical formulations. Compounds were separated using a Gemini C₁₈ (250 mm × 4.6 mm, 5 µm) Phenomenex^® column, at a temperature of 25 °C, with a mobile phase containing 10 mM of phosphoric acid (pH 3.29): acetonitrile (85.7:14.3, v/v) and a flow rate of 1.5 mL/min. Physicochemical characterization by TG, FTIR, and SEM of raw materials of LID, CFX, and EFX provided information useful for the evaluation, differentiation, and qualification of raw materials. Finally, the HPLC method was proved to be useful for evaluation of raw material and finished products, besides satisfying the need for an analytical method that allows simultaneous determination of EFX, CFX, and LID, which can also be extended to other matrices and applications.

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FTIR, TGA, and SEM are useful tools for the evaluation of the quality of APIs.

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A RP-HPLC method was developed and validated for the determination of LID, CFX, EFX.

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The proposed RP-HPLC method showed precise and accurate results in quality control.

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This method can be applied to the analysis of veterinary pharmaceutical products.

Hippeastrum reticulatum (Amaryllidaceae): Alkaloid Profiling, Biological Activities and Molecular Docking

The Amaryllidaceae family has proven to be a rich source of active compounds, which are characterized by unique skeleton arrangements and a broad spectrum of biological activities. The aim of this work was to perform the first detailed study of the alkaloid constituents of Hippeastrum reticulatum (Amaryllidaceae) and to determine the anti-parasitological and cholinesterase (AChE and BuChE) inhibitory activities of the epimers (6α-hydroxymaritidine and 6β-hydroxymaritidine). Twelve alkaloids were identified in H. reticulatum: eight known alkaloids by GC-MS and four unknown (6α-hydroxymaritidine, 6β-hydroxymaritidine, reticulinine and isoreticulinine) by NMR. The epimer mixture (6α-hydroxymaritidine and 6β-hydroxymaritidine) showed low activity against all protozoan parasites tested and weak AChE-inhibitory activity. Finally, a molecular docking analysis of AChE and BuChE proteins showed that isoreticulinine may be classified as a potential inhibitory molecule since it can be stabilized in the active site through hydrogen bonds, π-π stacking and hydrophobic interactions.

Taraxerol 4-Methoxybenzoate, an in vitro Inhibitor of Photosynthesis Isolated from Pavonia multiflora A. St-Hil. (Malvaceae)

A phytochemical study of Pavonia multiflora A. St-Hil. (Malvaceae) led to the isolation through chromatographic techniques of 10 secondary metabolites: vanillic acid (1), ferulic acid (2), p-hydroxybenzoic acid (3), p-coumaric acid (4), loliolide (5), vomifoliol (6), 4,5-dihydroblumenol A (7), 3-oxo-α-ionol (9), blumenol C (10), and taraxerol 4-methoxybenzoate (8), the latter being a novel metabolite. Their structures were identified by (1) H- and (13) C-NMR, using one- and two-dimensional techniques, and X-ray crystallography. In this work, we report the effect of compounds 5 and 8 on several photosynthetic activities in an attempt to search for new compounds as potential herbicide agents that affect photosynthesis. Both compounds inhibited the electron flow from H2 O to methyl viologen; therefore, they act as Hill reaction inhibitors. Using polarographic techniques and studies of the fluorescence of chlorophyll a, the interaction sites of these compounds were located at photosystem II.

Analysis of Bioactive Amaryllidaceae Alkaloid Profiles in Lycoris Species by GC-MS

The genus Lycoris, a group of Amaryllidaceae plants distributed in temperate regions of Eastern Asia, is already known for containing representative alkaloids typical of this botanical family with a wide range of biological activities (for example, lycorine and galanthamine). In the present work, the alkaloid profiles of nine species, L. albiflora, L. aurea, L. chinensis, L. haywardii, L. incarnata, L. longituba, L. radiata, L. sprengeri, and L. squamigera, and one variety ( L. radiata var. pumila) have been evaluated by GC-MS. Structures belonging to the lycorine-, homolycorine-, haemanthamine-, narciclasine-, tazettine-, montanine- and galanthamine-series were identified and quantified, with galanthamine- and lycorine-type alkaloids predominating and usually showing a high relative abundance in comparison with other alkaloids of the extracts. Interestingly, L. longituba revealed itself to be a potential commercial source of bioactive alkaloids. In general terms, our results are consistent with the alkaloid profiles reported in the literature for previously studied species.

Analysis of bioactive Amaryllidaceae alkaloid profiles in Lycoris species by GC-MS

The genus Lycoris, a group of Amaryllidaceae plants distributed in temperate regions of Eastern Asia, is already known for containing representative alkaloids typical of this botanical family with a wide range of biological activities (for example, lycorine and galanthamine). In the present work, the alkaloid profiles of nine species, L. albiflora, L. aurea, L. chinensis, L. haywardii, L. incarnata, L. longituba, L. radiata, L. sprengeri, and L. squamigera, and one variety (L. radiata var. pumila) have been evaluated by GC-MS. Structures belonging to the lycorine-, homolycorine-, haemanthamine-, narciclasine-, tazettine-, montanine- and galanthamine-series were identified and quantified, with galanthamine- and lycorine-type alkaloids predominating and usually showing a high relative abundance in comparison with other alkaloids of the extracts. Interestingly, L. longituba revealed itself to be a potential commercial source of bioactive alkaloids. In general terms, our results are consistent with the alkaloid profiles reported in the literature for previously studied species.