Antibacterial activities of Ligaria cuneifolia and Jodina rhombifolia leaf extracts against phytopathogenic and clinical bacteria

The Argentine mistletoes Ligaria cuneifolia (Ruiz & Pav.) Tiegh (Loranthaceae) and Phoradendron liga (Gillies ex Hook. & Arn.) Eichler (Santalaceae). Thirty years of research

Ligaria cuneifolia (Ruiz & Pav.) Tiegh (Loranthaceae) and Phoradendron liga (Gillies ex Hook. & Arn.) Eichler (Santalaceae) are regarded as Argentine mistletoes based on their similarities with the European counterpart, Viscum album L. (Santalaceae). These two species are the most used medicinal plants to treat high blood pressure in the Argentinian population. To provide scientific grounds to their traditional use and therapeutic potential, they were selected as herbal drug candidates. The main findings would support the anti-hypertensive action, the anticholesterolemic and antioxidant features of L. cuneifolia, and immunomodulatory properties for both species. Quercetin-O-glycosides, galloyl glycosides, and proanthocyanidins are present in L. cuneifolia while P. liga shows C-glycosyl flavones and 3-deoxyproanthocyanidins. This review summarizes the phytochemical characterization, medicinal properties and reveals promising results warranting future efforts for further investigation.

nor 3′-Demethoxyisoguaiacin from Larrea tridentata Is a Potential Alternative against Multidrug-Resistant Bacteria Associated with Bovine Mastitis

Bovine mastitis is one of the most common diseases in dairy cows, and it causes significant economic losses in dairy industries worldwide. Gram-positive and Gram-negative bacteria can cause bovine mastitis, and many of them have developed antimicrobial resistance. There is an urgent need for novel therapeutic options to treat the disease. Larrea tridentata-derived compounds represent an important potential alternative treatment. The aim of the present study was to isolate and characterize antibacterial compounds from Larrea tridentata against multidrug-resistant bacteria associated with bovine mastitis. The L. tridentata hydroalcoholic extract (LTHE) exhibited antibacterial activity. The extract was subjected to a bipartition, giving an aqueous fraction (moderate antibacterial activity) and an organic fraction (higher antibacterial activity). Chromatographic separation of the organic fraction enabled us to obtain four active sub-fractions. Chemical analyses through HPLC techniques were conducted for the LTHE, fractions, and sub-fraction Ltc1-F3, from which we isolated two compounds, characterized by ¹H and ¹³C NMR analyses. Compound nor-3 demethoxyisoguaiacin exhibited the best antibacterial activity against the evaluated bacteria (MIC: 0.01–3.12 mg/mL; MBC: 0.02–3.12 mg/mL). The results indicated that nor-3 demethoxyisoguaiacin can be used as an alternative treatment for multidrug-resistant bacteria associated with mastitis.

Antibacterial Potential of Caesalpinia coriaria (Jacq) Willd Fruit against Aeromonas spp. of Aquaculture Importance

Simple Summary

Aquaculture remains an important source of food, however, aquaculture systems are affected by different factors including the appearance of resistant or multiresistant bacteria to antimicrobials. An alternative in the search for new treatments for these bacteria is plant extracts. The aim of the present study was to determine the antibacterial activity of Caesalpinia coriaria fruit hydroalcoholic extract and gallic acid over Aeromonas hydrophila, Aeromonas veronii, and Aeromonas dhakensis to identify new molecules for the treatment of diseases caused by Aeromona spp. The hydroalcoholic extract of Caesalpinia coriaria and its fractions have antibacterial activity against Aeromonas hydrophila, Aeromonas veronii, and Aeromonas dhakensis and could be alternatives for the treatment of diseases caused by the genus Aeromonas.

Abstract

Aquaculture is an important source of food and livelihood for hundreds of millions of people around the world, however, aquaculture systems are affected by different factors, among them the appearance of resistant or multiresistant bacteria to antimicrobials. The secondary metabolites of plants have been proposed as alternatives for the treatment of these bacteria. The aim of the present study was to determine the antibacterial activity of Caesalpinia coriaria fruit hydroalcoholic extract and gallic acid over Aeromonas hydrophila, Aeromonas veronii,  and Aeromonas dhakensis to identify new molecules for the treatment of diseases caused by Aeromonas spp. The C. coriaria fruit hydroalcoholic extract (HECc) was obtained by hydroalcoholic maceration and subjected to bipartition with ethyl acetate and water to obtain an aqueous fraction (Ac-FrCc) and an organic fraction (Ac-FrEtCc); gallic acid was purchased commercially. The Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), MBC/MIC ratio, and cytotoxicity of HECc, its fractions, and gallic acid were determined. The results indicate that HECc fractions (Ac-FrCc and Ac-FrEtCc) and gallic acid have bactericidal activity against A. hydrophila and A. dhakensis, but only gallic acid showed bactericidal activity against A. veronii. The HECc and Ac-FrCc showed no toxicity, Ac-FrEtCc showed low toxicity, and gallic acid showed medium toxicity. The HECc, Ac-FrCc, and Ac-FrEtCc may be alternatives for the treatment of diseases caused by the genus Aeromonas, however, in vivo assays are necessary to corroborate these results.

Dynamics of Polyphenol Biosynthesis by Calli Cultures, Suspension Cultures and Wild Specimens of the Medicinal Plant Ligaria cuneifolia (Ruiz & Pav.) Tiegh. (Loranthaceae). Analysis of Their Biological Activity

Ligaria cuneifolia (R. et P.) Tiegh. (Loranthaceae) is a South American hemiparasitic species with antioxidant, antitumoral, antimicrobial, and antilipidemic activities attributed to its polyphenolic content. We studied the polyphenolic pattern of L. cuneifolia during different phenological stages: flowering, fruiting, and post-fruiting. The highest total phenolic content was found in stems at post-fruiting (214 ± 12.1 mg gallic acid eq·g^-1 DW) and fruiting (209 ± 13.7 mg gallic acid eq·g^-1 DW), followed by post-fruiting leaves (207 ± 17.5 mg gallic acid eq·g^-1 DW). Flavonoids accumulated at higher levels in leaves and hydroxycinnamic acids in leaves at flowering and post-fruiting. The polyphenolic pattern was similar between organs from wild plants and in vitro cultures, although at a significantly lower level in the latter ones. The performance of calli growing under a 16 h photoperiod in a modified White medium with 1-naphthalene acetic acid (2.50 μM) and Kinetin (9.20 μM) was better than in the dark. When calli grew in media only with auxins (IAA, NAA, and 2,4-D, all at 2.50 µM concentration), its growth and polyphenolic content improved. Cell suspensions with 2.50 µM NAA and 9.20 µM KIN grew slowly and produced very small amounts of polyphenols. As for the antioxidant activity, it was detected in all samples (approximately 1000 µmol trolox eq·g^-1 DW) except fruits, where a lower value was found (328 µmol trolox eq·g^-1 DW). In vitro cultures have the lowest antioxidant activity when compared to methanolic extracts from organs of wild specimens. Finally, antimutagenic or mutagenic activity in wild plants and in vitro culture extracts was not detected by the Ames test.

Exploring Phytochemicals for Combating Antibiotic Resistance in Microbial Pathogens

Antibiotic resistance or microbial drug resistance is emerging as a serious threat to human healthcare globally, and the multidrug-resistant (MDR) strains are imposing major hurdles to the progression of drug discovery programs. Newer antibiotic-resistance mechanisms in microbes contribute to the inefficacy of the existing drugs along with the prolonged illness and escalating expenditures. The injudicious usage of the conventional and commonly available antibiotics in human health, hygiene, veterinary and agricultural practices is proving to be a major driver for evolution, persistence and spread of antibiotic-resistance at a frightening rate. The drying pipeline of new and potent antibiotics is adding to the severity. Therefore, novel and effective new drugs and innovative therapies to treat MDR infections are urgently needed. Apart from the different natural and synthetic drugs being tested, plant secondary metabolites or phytochemicals are proving efficient in combating the drug-resistant strains. Various phytochemicals from classes including alkaloids, phenols, coumarins, terpenes have been successfully demonstrated their inhibitory potential against the drug-resistant pathogens. Several phytochemicals have proved effective against the molecular determinants responsible for attaining the drug resistance in pathogens like membrane proteins, biofilms, efflux pumps and bacterial cell communications. However, translational success rate needs to be improved, but the trends are encouraging. This review highlights current knowledge and developments associated challenges and future prospects for the successful application of phytochemicals in combating antibiotic resistance and the resistant microbial pathogens.

Impact of Moderate Cold and Salt Stress on the Accumulation of Antioxidant Flavonoids in the Leaves of Two Capsicum Cultivars

The horticultural production of bell peppers generates large quantities of residual biomass. Abiotic stress stimulates the production of protective flavonoids, so the deliberate application of stress to the plants after fruit harvest could provide a strategy to valorize horticultural residuals by increasing flavonoid concentrations, facilitating their industrial extraction. Here we exposed two Capsicum cultivars, a chilli and a bell pepper, to cold and salt stress and combinations thereof to determine their valorization potential. Noninvasive image-based phenotyping and multiparametric fluorescence measurements indicated that all stress treatments inhibited plant growth and reduced the leaf chlorophyll fluorescence index, with the chilli cultivar showing greater sensitivity. The fluorescence-based FLAV index allowed the noninvasive assessment of foliar luteolin glycosides. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis showed that moderate cold increased the levels of two foliar antioxidant luteolin glycosides in both cultivars, with bell pepper containing the highest amounts (induced to maximum 5.5 mg g^-1 DW cynaroside and 37.0 mg g^-1 DW graveobioside A) after combined stress treatment. These data confirm the potential of abiotic stress for the valorization of residual leaf biomass to enhance the industrial extraction of antioxidant and bioactive flavonoids.

Fatty Acids from Hermetia illucens Larvae Fat Inhibit the Proliferation and Growth of Actual Phytopathogens

The rapid increase of plant diseases caused by bacterial phytopathogens calls for an urgent search for new antibacterials. Antimicrobial compounds of natural origin stand up as frontiers in the attempts of the antibiotic overuse replacement. With this in mind, the Hermetia illucens (H. illucens) larvae have recently gained attention as a promising approach to fulfill this need. This study aimed to isolate the active constituents of H. illucens larvae fat and to estimate its antimicrobial capacity. We discovered the best composition of extracting solution retaining the pronounced antimicrobial activity of the extract. Using gas chromatography-mass spectrometry (GC-MS), we identified the unique natural array of fatty acids as the major constituents of the acidified water-methanol extract (AWME) as having new antimicrobial potency. In standard turbidimetric assay, the minimum inhibitory concentration (MIC) of the AWME was 0.78 mg/mL after 24 h of incubation for all five tested phytopathogenic bacteria strains: Pantoea agglomerans, Xanthomonas campestris, Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, and Dickeya solani. The minimum bactericidal concentration (MBC) ranged from 0.78 to 1.56 mg/mL against all tested strains after 24 h of incubation. The inhibition zone size of AWME (INZ) at 50 mg/mL concentration was in the range 12.2 ± 0.56 to 19.0 ± 0.28 mm, while zone size for the positive control (penicillin-streptomycin) (5000 IU/mL-5000 µg/mL) was in the scale of 20.63 ± 0.53 to 24.0 ± 0.35 mm as revealed by standard disk diffusion assay. For the first time, our findings indicated the substantial antibacterial potential of AWME of H. illucens larvae fat against these actual phytopathogens, thus paving the way for further research to determine the mechanism of action in crop protection.

Antioxidant Activity of Flavonoid Rich Fraction of Ligaria cuneifolia (Loranthaceae)

Ligaria cuneifolia (Ruiz & Pav.) Tiegh. (Loranthaceae), the 'Argentine mistletoe', is a hemiparasite species largely used in folk medicine. The aim of this study was to evaluate the antioxidant activity using in vitro, ex vivo, and in vivo methods. A screening of phenolics was performed by UV spectroscopy on different fractions. The antioxidant capacity was evaluated in vitro by the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH^. ) assay on a crude extract (CE), ethyl acetate fraction (EAF), and aqueous fraction (AF). The results suggest that EAF concentrates the antioxidant capacity and was selected for further analysis. Capillary electrophoresis was employed to monitor the individual antioxidant capacity and the potential contributors to this effect. Ex vivo assays showed an efficient inhibition of tert-butyl hydroperoxide-induced rat liver phospholipid oxidation, as well as rat brain autoxidation, and H₂ O₂ -induced DNA damage in blood monocytes. In vivo, the topical application of EAF significantly decreased skin chemiluminescence in a mice model.

Effect of parasitism of Lernaea cyprinacea on tadpoles of the invasive species Lithobates catesbeianus

The introduction of invasive species is one of the greatest threats currently faced by natural ecosystems, causing ecological imbalances between native populations and transmission of a variety of diseases. We reported the interaction between two exotic species given by the parasitic infestation of the copepod Lernaea cyprinacea in the early stages of the development of the American bullfrog Lithobates catesbeianus in the central area of Argentina. In this paper we analysed the leukocyte profile of parasitized and non-parasitized tadpoles of L. catesbeianus with L. cyprinacea and their body condition (BC) as biomarkers of the health status of organisms. A total of 27 tadpoles of L. catesbeianus were analysed (12 non-parasitized and 15 parasitized). The lower BC recorded in parasitized organisms show a lower health status in these tadpoles, which could be affecting the metamorphosis and therefore impact at the population level. Leukocyte response of L. catesbeianus tadpoles to the parasitism of L. cyprinacea was found. Mature and immature lymphocyte frequencies and hematocrit were higher in parasitized compared to non-parasitized tadpoles, which is a typical response to the presence of parasites. However, eosinophils and monocytes were recorded at high frequencies in not parasitized tadpoles, which could be due to the important role played by these leucocytes in the metamorphosis of frogs. The results of this study constitute a first antecedent on leukocyte profile in aquatic stages of anurans during an ectoparasitosis and its possible implications for environmental health. The parasitism of L. cyprinacea influences the biology of the American bullfrog at both the individual and population levels. Parasitized individuals are not killed directly by the parasite, but they can create conditions for secondary infections, growth retardation, behavioral changes and, ultimately, reduce populations.

Bioactivities of Flavonoids from Lopezia racemosa

Lopezia racemosa Cav. (Onagraceae) has been used in Mexican traditional medicine to alleviate stomachache, biliary colic, urine retention, stomach cancer, and skin, dental, buccal, and urinary infections. The objective of this study was to determine the bioactivities of specific parts of the plant to scientifically confirm its traditional use. Aerial parts and flowers were macerated and subsequently extracted with hexane, chloroform, and methanol. This study was focused on the analysis of polar components, and thus the methanolic fractions were selected for further investigations. These fractions were evaluated for their antimicrobial activity using a panel of bacterial Gram-positive and -negative strains, as well as fungal strains, including filamentous fungi and yeasts. In addition, the cytotoxic activity of the extract was assessed by MTT using the human-derived monocytic THP-1 and the normal human fibroblast cell lines. Various fractions showed antimicrobial activity against various pathogens, although the most relevant were against Pseudomonas aeruginosa and Trichophyton mentagrophytes. No inhibition of yeasts was recorded. Only four fractions showed cytotoxic effects when the human-derived THP-1 and fibroblast cells were assessed. The four flavonoids isolated from the extract were luteolin, luteolin-6-C-hexoside, luteolin-8-C-hexoside, and hyperoside. The biological activities presented in this study validate some traditional uses of the plant.

Identification of Antibacterial Phenolics in Selected Plant Species from Mexican Cloud Forest by Mass Spectrometry Dereplication

Fifteen plant species from a protected cloud forest (CF) in Veracruz, Mexico, were screened for their in vitro capacity to inhibit the growth of the phytopathogenic bacteria Chryseobacterium sp., Pseudomonas cichorii, Pectobacterium carotovorum and Pantoea stewartii, causal agents of damage to crops like 'chayote', lettuce, potato and corn. As a result, the bioactivity of Turpinia insignis and Leandra cornoides is reported for the first time against Chryseobacterium sp. and P. cichorii. In addition, 24 and 18 compounds not described for these species were dereplicated by an UPLC/MS-MS method, respectively. The identified compounds included simple phenols, hydroxycinnamic acids, flavonoids and coumarins. The antibacterial assay of 12 of them demonstrated the bacteriostatic effect of vanillin, trans-cinnamic acid, scopoletin and umbelliferone against Chryseobacterium sp. These findings confirm for the first time the value of the CF plants from Veracruz as sources of bioactive natural products with antimicrobial properties against phytopathogenic bacteria.

Antifungal activity and cytotoxicity of extracts and triterpenoid saponins obtained from the aerial parts of Anagallis arvensis L

ETHNOPHARMACOLOGICAL RELEVANCE

Anagallis arvensis L. (Primulaceae) is used in argentinean northwestern traditional medicine to treat fungal infections. We are reporting the isolation and identification of compounds with antifungal activity against human pathogenic yeast Candida albicans, and toxicity evaluation.

AIM OF THE STUDY

to study the antifungal activity of extracts and purified compounds obtained form A. arvensis aerial parts, alone and in combinations with fluconazole (FLU), and to study the toxicity of the active compounds.

MATERIALS AND METHODS

Disk diffusion assays were used to perform an activity-guided isolation of antifungal compounds from the aerial parts of A. arvensis. Broth dilution checkerboard and viable cell count assays were employed to determine the effects of samples and combinations of FLU + samples against Candida albicans. The chemical structures of active compounds were elucidated by spectroscopic analysis. Genotoxic and haemolytic effects of the isolated compounds were determined.

RESULTS

Four triterpenoid saponins (1-4) were identified. Anagallisin C (AnC), exerted the highest inhibitory activity among the assayed compounds against C. albicans reference strain (ATCC 10231), with MIC-0 =1µg/mL. The Fractional Inhibitory Concentration Index (FICI=0.129) indicated a synergistic effect between AnC (0.125µg/mL) and FLU (0.031µg/mL) against C. albicans ATCC 10231. AnC inhibited C. albicans 12-99 FLU resistant strain (MIC-0 =1µg/mL), and the FICI=0.188 indicated a synergistic effect between AnC (0.125µg/mL) and fluconazole (16µg/mL). The combination AnC+ FLU exerted fungicidal activity against both C. albicans strains. AnC exerted inhibitory activity against C. albicans ATCC 10231 sessile cells (MIC₅0=0.5µg/mL and MIC₈₀=1µg/mL) and against C. albicans 12-99 sessile cells (MIC₅0=0.75µg/mL and MIC₈₀=1.25µg/mL). AnC exerted haemolytic effect against human red blood cells at 15µg/mL and did not exerted genotoxic effect on Bacillus subtilis rec strains.

CONCLUSIONS

The antifungal activity and lack of genotoxic effects of AnC give support to the traditional use of A. arvensis as antifungal and makes AnC a compound of interest to expand the available antifungal drugs.

Development of a novel dual CD-MEKC system for the systematic flavonoid fingerprinting of Ligaria cuneifolia (R. et P.) Tiegh.-Loranthaceae-extracts

The present work deals with the development and validation of a novel dual CD-MEKC system for the systematic flavonoid fingerprinting of Ligaria cuneifolia (R. et P.) Tiegh.-Loranthaceae-extracts. The BGE consisted of 20 mM pH 8.3 borate buffer, 50 mM SDS, a dual CD system based on the combination of 5 mM β-CD and 2% w/v S-β-CD, and 10% v/v methanol. The proposed method has been successfully applied to the comparative analysis of extracts from aerial parts and different hosts, geographical areas, and extraction procedures in order to establish the flavonoid fingerprint of L. cuneifolia. The method was validated according to international guidelines. LOD and LOQ, intra and interday precision, and linearity were determined for catechin, epicatechin, procyanidin B2, rutin, quercetin-3-O-glucoside, quercetin-3-O-xyloside, quercetin-3-O-rhamnoside, quercetin-3-O-arabinofuranoside, quercetin-3-O-arabinopyranoside, and quercetin. The CD-MEKC methodology emerges as a suitable alternative to the traditional HPLC for quality control, fingerprinting, and standardization of L. cuneifolia extracts from different sources.

General Overview of Phenolics from Plant to Laboratory, Good Antibacterials or Not

The emergence and rapid development of seriously drug-resistant pathogens have created the greatest danger to public health and made the treatment of infectious diseases ineffective; to control the antibiotic-resistant microbes, the discovery of new effective antibacterials with new mechanisms of action against bacteria remains an urgent task to control the bacterial resistance. The paucity of infections in wild plants supports the role of innate defense system of plants. Many researchers nominate the natural extracts to act against bacterial resistance mechanisms, and the majority of them have now been focused on the combination of plant extracts and antibiotics to define the availability of resistance modification agents. Only very few numbers of natural products are successful to reach experiments circle beyond the in vitro assays. Phenols and phenolic acids could serve as good candidates to the natural antibacterial arsenal. The pyrogallol-based compounds are more potent than others such as catechol or resorcinol, gallic acid, and the hydroxycinnamic acid (ferulic acid) are destructing the bacterial cell wall of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, leading to leakage of cellular contents. These compounds have stronger activity against Gram-positive microorganisms, and some of them showed good synergism with antibiotics, for example, pentagalloylglucopyranose, is shown a synergism with penicillin G against methicillin-resistant S. aureus, another example is the interesting synergism between epicatechin gallate and oxacillin where the minimal inhibitory concentrations of oxacillin reduced around 500 times by the addition of epicatechin gallate to the antibiotic.

Identification and Characterization of Bioactive Compounds Targeting UropathogenicEscherichia colifrom Sanjin Tablets

Sanjin Tablets are completely natural preparation with significant efficacy in treating urinary tract infection. To identify the bioactive compounds from Sanjin Tablets, we separated components capable of binding to the soluble proteins of uropathogenicEscherichia coli(UPEC) by affinity binding and characterized their identities using liquid chromatography-mass spectrometry (LC-MS) analysis. Our study discovered eight compounds withE. coliprotein-binding capabilities, and all these compounds were tracked back to the original natural ingredients of Sanjin Tablets. These compounds presented essentially no antibacteria activity, indicating that they affect UPEC by means other than directly killing the cells. Further molecular modeling analysis predicted molecular targets for these compounds and mapped the residues potentially involved in compound-target interactions. All the predicted targets turned out to be critical proteins regulating the metabolisms ofE. coli, suggesting that these compounds may affect metabolic pathways in UPEC and inhibit pathogenesis. These data will benefit future design of drugs with higher efficacy and specificity on targeting pathogenic bacteria.