Therapeutic Potential of Plants as Anti-microbials for Drug Discovery

Unraveling antiviral efficacy of multifunctional immunomodulatory triterpenoids against SARS-COV-2 targeting main protease and papain-like protease

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may be over, but its variants continue to emerge, and patients with mild symptoms having long COVID is still under investigation. SARS-CoV-2 infection leading to elevated cytokine levels and suppressed immune responses set off cytokine storm, fatal systemic inflammation, tissue damage, and multi-organ failure. Thus, drug molecules targeting the SARS-CoV-2 virus-specific proteins or capable of suppressing the host inflammatory responses to viral infection would provide an effective antiviral therapy against emerging variants of concern. Evolutionarily conserved papain-like protease (PLpro) and main protease (Mpro) play an indispensable role in the virus life cycle and immune evasion. Direct-acting antivirals targeting both these viral proteases represent an attractive antiviral strategy that is also expected to reduce viral inflammation. The present study has evaluated the antiviral and anti-inflammatory potential of natural triterpenoids: azadirachtin, withanolide_A, and isoginkgetin. These molecules inhibit the Mpro and PLpro proteolytic activities with half-maximal inhibitory concentrations (IC50) values ranging from 1.42 to 32.7 μM. Isothermal titration calorimetry (ITC) analysis validated the binding of these compounds to Mpro and PLpro. As expected, the two compounds, withanolide_A and azadirachtin, exhibit potent anti-SARS-CoV-2 activity in cell-based assays, with half-maximum effective concentration (EC50) values of 21.73 and 31.19 μM, respectively. The anti-inflammatory roles of azadirachtin and withanolide_A when assessed using HEK293T cells, were found to significantly reduce the levels of CXCL10, TNFα, IL6, and IL8 cytokines, which are elevated in severe cases of COVID-19. Interestingly, azadirachtin and withanolide_A were also found to rescue the decreased type-I interferon response (IFN-α1). The results of this study clearly highlight the role of triterpenoids as effective antiviral molecules that target SARS-CoV-2-specific enzymes and also host immune pathways involved in virus-mediated inflammation.

Investigation of bioactive components responsible for the antibacterial and anti-biofilm activities of Caroxylon volkensii by LC-QTOF-MS/MS analysis and molecular docking

Caroxylon volkensii is a wild desert plant of the family Amaranthaceae. This study represents the first report of the metabolomic profiling of C. volkensii by liquid chromatography quadrupole-time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS). The dereplication study of its secondary metabolites led to the characterization of 66 known compounds. These compounds include catecholamines, tyramine derivatives, phenolic acids, triterpenoids, flavonoids, and others. A new tyramine derivative, alongside other known compounds, was reported for the first time in the Amaranthaceae family. The new derivative and the first-reported compounds were putatively identified through MS/MS fragmentation data. Given the notorious taxonomical challenges within the genus Salsola, to which C. volkensii previously belonged, our study could offer a valuable insight into its chemical fingerprint and phylogenetic relationship to different Salsola species. The antibacterial potential of C. volkensii methanolic extract (CVM) against Pseudomonas aeruginosa was screened. The minimum inhibitory concentration (MIC) of CVM ranged from 32 to 256 μg mL-1. The anti-quorum sensing potential of CVM resulted in a decrease in the percentage of strong and moderate biofilm-forming isolates from 47.83% to 17.39%. It revealed a concentration-dependent inhibitory activity on violacein formation by Chromobacterium violaceum. Moreover, CVM exhibited an in vivo protective potential against the killing capacity of P. aeruginosa isolates. A molecular docking study revealed that the quorum-sensing inhibitory effect of CVM can be attributed to the binding of tyramine conjugates, ethyl-p-digallate, and isorhamnetin to the transcriptional global activator LasR.

Investigation of phytochemical composition and bioactivity evaluation of extracts from Myrsine umbellata Mart

The objective of the study was to carry out phytochemical prospection through colorimetric tests to determine the groups of secondary metabolites and also to determine the total content of phenolic compounds (TPC) present in plant extracts methanol (ME), ethyl acetate (EAE), hexane (HE) and dichloromethane (DE) from the leaves of Myrsine umbellata, as well as to investigate the antimicrobial activity against twelve standard ATCC strains by the broth microdilution technique; the antioxidant potential by the DPPH method and the ABTS method and the antibiofilm potential on the biofilm biomass of standard bacteria by the crystal violet technique and tetrazolium salt reduction (MTT) assay. Phytochemical prospection detected the presence of saponins, steroids, alkaloids, anthocyanins, anthocyanidins, flavonoids, and tannins. The results of the quantitative phytochemical estimation revealed a higher content of total phenolics in DE (280.24 ± 0.037 µM GAE g ext. -1) followed by ME (159.01 ± 0.031 µM GAE g ext. -1). The ME showed the best biological activities when compared to the other extracts tested. We observed antimicrobial activity against Gram-positive Staphylococcus epidermidis strain (MIC 3.12 and MBC 6.25), antioxidant percentage of 92.58% against the DPPH radical and 420.31 µM Trolox g ext. -1 against the ABTS radical, finally showed antibiofilm action against Gram-positive strain Staphylococcus aureus, with eradication of the biomass in 92.58%. The results suggest that EM from M. umbellata represents an alternative source of plant bioactives for the development of natura products.

Chemical Diversity and Medicinal Potential of Vitex negundo L.: From Traditional Knowledge to Modern Clinical Trials

BACKGROUND

In Vedic context, Nirgundi (V. negundo) has been utilized for its anti-inflammatory, analgesic, and wound-healing properties. It has been employed to alleviate pain, treat skin conditions, and address various ailments. The plant's leaves, roots, and seeds have all found applications in traditional remedies. The knowledge of Nirgundi's medicinal benefits has been passed down through generations, and it continues to be a part of Ayurvedic and traditional medicine practices in India.

DISPEL: database for ascertaining the best medicinal plants to cure human diseases

Medicinal plants are anticipated to be one of the most valuable resources for the remedial usage in the treatment of various ailments. The data on key medicinal plants and their therapeutic efficacy against various ailments are quite scattered and not available on a single platform. Moreover, currently there is no means/mechanism of finding the best medicinal plant(s) from numerous plants known to cure any disease. DISPEL (Diseases Plants Eliminate) is a compendium of medicinal plants available across the world that are used to cure infectious as well as non-infectious diseases in humans. The association of a medicinal plant with a disease it cures is hereby referred to as 'medicinal plant-disease cured' linkage. The DISPEL database hosts ∼60 000 'medicinal plant-disease cured' linkages encompassing ∼5500 medicinal plants and ∼1000 diseases. This platform provides interactive and detailed visualization of medicinal plants, diseases and their relations using comprehensible network graph representation. The user has the freedom to search the database by specifying the name of disease(s) as well as the scientific/common name(s) of plant. Each 'medicinal plant-disease cured' relation is scored based on the availability of any medicine/product derived from that medicinal plant, information about active compound(s), knowledge regarding the part of plant that is effective and number of distinct articles/books/websites confirming the effectiveness of the medicinal plant. The user can find the best plant(s) that can be used to cure any desired disease(s). The DISPEL database is the first step towards generating the 'most-effective' combination of plants to cure a disease since it delineates as well as ranks all the therapeutic medicinal plants for that disease. The combination of best medicinal plants can then be used to conduct clinical trials and thus pave the way for their use in clinics for treatment of diseases. Database URL https://compbio.iitr.ac.in/dispel.

Inhibition of the norA gene expression and the NorA efflux pump by the tannic acid

The NorA efflux pump of Staphylococcus aureus is known to play a major role in the development of resistance against quinolone drugs by reducing their concentration inside target pathogens. The objective of this study was to evaluate the ability of tannic acid to inhibit the gene expression of the NorA efflux pump in Staphylococcus aureus and to evaluate the in silico effect on the pump. Efflux pump inhibition was evaluated by fluorimetry. The checkerboard method evaluates the effect of the test substance in combination with an antimicrobial at different concentrations. To gene expression evaluation NorA the assay was performed using: a sub-inhibitory concentration preparation (MIC/4) of the antibiotic; a sub-inhibitory concentration preparation (MIC/4) of the antibiotic associated with tannic acid at a sub-inhibitory concentration (MIC/4). In this study, docking simulations were performed by the SWISSDOCK webserver. The ability of tannic acid to inhibit the NorA efflux pump can be related to both the ability to inhibit the gene expression of this protein, acting on signaling pathways involving the ArlRS membrane sensor. As well as acting directly through direct interaction with the NorA protein, as seen in the approach and in silico and in vitro per checkerboard method and fluorimetry of bromide accumulated in the cell.

Interaction of Laurusides 1 and 2 with the 3C-like Protease (Mpro) from Wild-Type and Omicron Variant of SARS-CoV-2: A Molecular Dynamics Study

Laurus nobilis (bay laurel) is a natural source of biological compounds, and some of its extracts and phytocompounds are also endowed with antiviral activity toward the family of the severe acute respiratory syndrome (SARS)-associated β-coronaviruses. Some glycosidic laurel compounds such as laurusides were proposed as inhibitors of important protein targets of SARS-CoV-2, which clearly recalls their potential as anti-COVID-19 drugs. Due to the frequent genomic variations of the β-coronaviruses and the consequent importance of evaluating a new drug candidate with respect to the variants of the target β-coronavirus, we decided to investigate at an atomistic level the molecular interactions of the potential laurel-derived drugs laurusides 1 and 2 (L01 and L02, respectively) toward a well-conserved and crucial target, the 3C-like protease (Mpro), using the enzymes of both the wild-type of SARS-CoV-2 and of the more recent Omicron variant. Thus, we performed molecular dynamic (MD) simulations of laurusides—SARS-CoV-2 protease complexes to deepen the knowledge on the stability of the interaction and compare the effects of the targeting among the two genomic variants. We found that the Omicron mutation does not significantly impact the lauruside binding and that L02 connects more stably with respect to L01 in the complexes from both variants, even though both compounds prevalently interact within the same binding pocket. Although purely in silico, the current study highlights the potential role of bay laurel phytocompounds in the antiviral and specifically anti-coronavirus research and shows their potential binding toward Mpro, corroborating the important commitment of bay laurel as functional food and disclosing novel scenarios of lauruside-based antiviral therapies.

Therapeutic Potential of Flavonoids and Tannins in Management of Oral Infectious Diseases-A Review

Medicinal plants are rich sources of valuable molecules with various profitable biological effects, including antimicrobial activity. The advantages of herbal products are their effectiveness, relative safety based on research or extended traditional use, and accessibility without prescription. Extensive and irrational usage of antibiotics since their discovery in 1928 has led to the increasing expiration of their effectiveness due to antibacterial resistance. Now, medical research is facing a big and challenging mission to find effective and safe antimicrobial therapies to replace inactive drugs. Over the years, one of the research fields that remained the most available is the area of natural products: medicinal plants and their metabolites, which could serve as active substances to fight against microbes or be considered as models in drug design. This review presents selected flavonoids (such as apigenin, quercetin, kaempferol, kurarinone, and morin) and tannins (including oligomeric proanthocyanidins, gallotannins, ellagitannins, catechins, and epigallocatechin gallate), but also medicinal plants rich in these compounds as potential therapeutic agents in oral infectious diseases based on traditional usages such as Agrimonia eupatoria L., Hamamelis virginiana L., Matricaria chamomilla L., Vaccinium myrtillus L., Quercus robur L., Rosa gallica L., Rubus idaeus L., or Potentilla erecta (L.). Some of the presented compounds and extracts are already successfully used to maintain oral health, as the main or additive ingredient of toothpastes or mouthwashes. Others are promising for further research or future applications.

Simultaneous Optimization of Phenolic Compounds and Antioxidant Abilities of Moroccan Pimpinella anisum Extracts Using Mixture Design Methodology

Pimpinella anisum (anise) is a dense vegetal matrix with considerable amounts of bioactive components known for its pharmacological properties. The optimization of extraction constitutes an important key to improving efficacy and avoiding wasting time. Within this framework, the present study was designed to select the most appropriate extractor solvent mixture to extract phenolic and flavonoids using Mixture Design Methodology. The concerned responses were the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant ability examined by 2,2-diphenyl-l-picrylhydrazyl (DPPH) assay. Before mixture design optimization, a screening of solvents was conducted on ten polar and nonpolar solvents to choose the best solvents that give a maximum of total phenolic compounds. This first step has shown that water, ethanol and methanol were the best-used solvents. Later, an augmented centroid design investigated the solvent system’s optimization. The results of simultaneous optimization have shown that the ternary mixture containing 44% of water, 22% of ethanol and 34% of methanol was the most appropriate for simultaneous maximization of TPC, TFC and antioxidant activity with 18.55 mg GAE/g, 7.16 mg QE/g and 0.56 mg/mL, respectively. Our results have shown that using mixture design as an optimization technique was an excellent way to choose the most suitable mixture to extract bioactive compounds, which may represent a promising method of multi-purpose extraction, especially in the pharmaceutical and food sectors.

Ethnobotanical Survey of Plants Used by Subsistence Farmers in Mitigating Cabbage and Spinach Diseases in OR Tambo Municipality, South Africa

Annually, significant crop losses are reported due to diseases caused by phytopathogens. Most subsistence farmers cannot afford the high cost of chemical treatments thereby resulting in the increasing dependence on plant extracts to manage crop diseases. In this study, we documented plants used for the management of cabbage and spinach diseases in OR Tambo Municipality, Eastern Cape Province. An ethnobotanical survey using semi-structured questionnaires was used to document plants and plant parts used by the subsistence farmers in managing cabbage and spinach diseases. Semi-structured questionnaires were administered to 41 consenting subsistence farmers from November to December in 2021, using snowball sampling. The collected data were subjected to descriptive statistical and ethnobotanical analyses. A total of 17 plants belonging to 10 families were identified by the participants as being used in mitigating cabbage and spinach diseases. Tulbaghia violacea, Aloe ferox, and Capsicum annuum had the highest use value of 0.32 each, whereas Tulbaghia violacea had the highest relative frequency of citation of 0.39. This current study revealed the importance of plants in managing crop diseases in local communities. It provides baseline data for future pharmacological evaluations in authenticating the efficacies of the identified plants in managing crop diseases.

Natural acylated flavonoids: their chemistry and biological merits in context to molecular docking studies

Acylated flavonoids are widely distributed natural dietary bioactives with several health attributes. A large diversity of acylated flavonoids with interesting biological potentialities were reported. Of these, 123 compounds with potential antimicrobial, antiparasitic, anti-inflammatory, anti-nociceptive, analgesic and anti-complementary effects were selected from several databases. Based upon these data, the possible mechanistic evidence for their effects were reported. Generally, aromatic acyls i.e., galloyl derivatives appeared to improve efficacy through enhancement of the binding affinities to molecular targets due to plenty of donating and accepting centers. Docking simulations conducted by Molecular Operating Environment (MOE) of acylated flavonoids revealed that compound 12 is at the top of the list into the antibacterial target DNA gyrase subunit B (GyrB), from E. coli, followed by compounds 10, 4 and 23. Compounds 81, 88, 96, 92, 99, 100, 102 and 103 have the strongest binding affinities into Human matrix metallopeptidase (MMP) 2 and 9 catalytic domains. Compound 103 exerted the most balanced predicted dual MMP-2/MMP-9 inhibition action. Compound 95 recorded the strongest binding affinity into metabotropic glutamate receptor (mglur1) with the lowest energy conformer. The data presented in this review suggests that these candidate acylated flavonoids ought to be considered in future drug developments especially as anti-inflammatory and antimicrobial agents.

A Systematic Review on Antimicrobial and Antiparasitic Activity of Eurycoma longifolia Jack (Tongkat Ali)

Eurycoma longifolia or Tongkat Ali (family: Simaroubaceae) has the potential to be utilised as an antimicrobial and antiparasitic agent that correlated with its traditional use to treat jaundice, malaria, antiseptic agent, and many more. This review is aimed at systematically sieving through articles regarding the antimicrobial and antiparasitic activity of E. longifolia. A total of 123 studies have been found using suitable keywords and manually searched from previous studies through the four databases. After title screening and abstract examination, 56 articles were excluded due to duplication and not meeting the acceptance criteria. 67 articles were assessed on full-text accessibility, 31 studies remained, and this number decreased to 20 articles after a careful examination of the full-text articles. Among the 20 articles selected, 17 articles proved the potential of E. longifolia as an antimicrobial and antiparasitic agent efficiently. 2 selected articles showed partial positive results, which specified specific microorganisms tested. In contrast, another 1 article gave a completely negative result. As for the conclusion, current studies highlighted by this review may shed light on the future direction of studies concerning E. longifolia as a novel antimicrobial and antiparasitic agent. However, more research should be done in the future focusing on the efficiency of E. longifolia for veterinary medicine utilisation.

Multiple health benefits of curcumin and its therapeutic potential

Turmeric, or Curcuma longa as it is formally named, is a multifunctional plant with numerous names. It was dubbed "the golden spice" and "Indian saffron" not only for its magnificent yellow color, but also for its culinary use. Turmeric has been utilized in traditional medicine since the dawn of mankind. Curcumin, demethoxycurcumin, and bisdemethoxycurcumin, which are all curcuminoids, make up turmeric. Although there have been significant advancements in cancer treatment, cancer death and incidence rates remain high. As a result, there is an increasing interest in discovering more effective and less hazardous cancer treatments. Curcumin is being researched for its anti-inflammatory, anti-cancer, anti-metabolic syndrome, neuroprotective, and antibacterial properties. Turmeric has long been used as a home remedy for coughs, sore throats, and other respiratory problems. As a result, turmeric and its compounds have the potential to be used in modern medicine to cure a variety of diseases. In this current review, we highlighted therapeutic potential of curcumin and its multiple health benefits on various diseases.

HPLC-DAD Based Polyphenolic Profiling and Evaluation of Pharmacological Attributes of Putranjiva roxburghii Wall

The current study was intended to explore the phytochemical profiling and therapeutic activities of Putranjiva roxburghii Wall. Crude extracts of different plant parts were subjected to the determination of antioxidant, antimicrobial, antidiabetic, cytotoxic, and protein kinase inhibitory potential by using solvents of varying polarity ranges. Maximum phenolic content was notified in distilled water extracts of the stem (DW-S) and leaf (DW-L) while the highest flavonoid content was obtained in ethyl acetate leaf (EA-L) extract. HPLC-DAD analysis confirmed the presence of various polyphenols, quantified in the range of 0.02 ± 0.36 to 2.05 ± 0.18 μg/mg extract. Maximum DPPH scavenging activity was expressed by methanolic extract of the stem (MeOH-S). The highest antioxidant capacity and reducing power was shown by MeOH-S and leaf methanolic extract (MeOH-L), respectively. Proficient antibacterial activity was shown by EA-L extract against Bacillus subtilis and Escherichia coli. Remarkable α-amylase and α-glucosidase inhibition potential was expressed by ethyl acetate fruit (EA-F) and n-Hexane leaf (nH-L) extracts, respectively. In case of brine shrimp lethality assay, 41.67% of the extracts (LC₅₀ < 50 µg/mL) were considered as extremely cytotoxic. The test extracts also showed mild antifungal and protein kinase inhibition activities. The present study explores the therapeutic potential of P. roxburghii and calls for subsequent studies to isolate new bioactive leads through bioactivity-guided isolation.

Hydrolyzable tannins (ellagitannins), flavonoids, pentacyclic triterpenes and their glycosides in antimycobacterial extracts of the ethnopharmacologically selected Sudanese medicinal plant Combretum hartmannianum Schweinf

In Sudanese traditional medicine, decoctions, macerations, and tonics of the stem and root of Combretum hartmannianum are used for the treatment of persistent cough, a symptom that could be related to tuberculosis (TB). To verify these traditional uses, extracts from the stem wood, stem bark, and roots of C. hartmannianum were screened for their growth inhibitory effects against Mycobacterium smegmatis ATCC 14468. Methanol Soxhlet and ethyl acetate extracts of the root gave the strongest effects (MIC 312.5 and 625 µg/ml, respectively). HPLC-UV/DAD and UHPLC/QTOF-MS analysis of the ethyl acetate extract of the root led to the detection of 54 compounds, of which most were polyphenols and many characterized for the first time in C. hartmannianum. Among the major compounds were terflavin B and its two isomers, castalagin, corilagin, tellimagrandin I and its derivative, (S)-flavogallonic acid dilactone, punicalagin, and methyl-ellagic acid xylopyranoside. In addition, di-, tri- and tetra-galloyl glucose, combregenin, terminolic acid, cordifoliside D, luteolin, and quercetin-3-O-galactoside-7-O-rhamnoside-(2→1)-O-β-D-arabinopyranoside were characterized. Luteolin gave better growth inhibition against M. smegmatis (MIC 250 µg/ml) than corilagin, ellagic acid, and gallic acid (MIC 500-1000 µg/ml). Our study justifies the use of C. hartmannianum in Sudanese folk medicine against prolonged cough that could be related to TB infection. This study demonstrates that C. hartmannianum should be explored further for new anti-TB drug scaffolds and antibiotic adjuvants.

Herbal plants as immunity modulators against COVID-19: A primary preventive measure during home quarantine

The novel coronavirus or severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is a deadly virus which has spread globally and claimed millions of lives. This novel virus transmits mainly through droplets and close human contact. It’s impact in different countries varies depending on geographical location, climatic conditions, food habits, and cultural activities. Several precautionary measures, as well as many medicines, are applied in different combinations to limit the spread of infection. This results in a preliminary relief of people infected in the first stage of infection. An alternative approach has been introduced which proposes natural herbs, which have minimal or no side effects, and improve overall immunity. Some essential herbs with their immunomodulatory effects are mentioned in this article along with suggestions for improved immunity and protection.

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.

Antimicrobial Activity of Extracts from the Humiria balsamifera (Aubl)

Humiria balsamifera (Aubl), commonly known as "mirim", is a plant of the Humiriaceae family, which consists of 39 species divided between eight genera: Duckesia, Endopleura, Humiria, Humiriastrum, Hylocara, Sacoglottis, Schistostemon, and Vantenea. This study aimed to characterize H. balsamifera extracts by LC-MS/MS and evaluate their antimicrobial potential through in vitro and in vivo assays. The leaves and stem bark of H. balsamifera were collected and dried at room temperature and then ground in a knife mill. The extracts were prepared with organic solvents in order to increase the polarity index (hexane, ethyl acetate, and methanol). The antimicrobial effects of these extracts were evaluated against the following bacterial strains: Escherichia coli ATCC 25922, Listeria monocytogenes ATCC 15313, Salmonella enterica Typhimurium ATCC 14028, and Staphylococcus aureus ATCC 6538. The best activity was observed in the ethyl acetate (EALE = 780 µg/mL), methanol (MLE = 780 µg/mL), and hexane (HLE = 1560 µg/mL) leaf extracts against S. aureus. Considering the results for both antimicrobial and antibiofilm activities, the EALE extract was chosen to proceed to the infection assays, which used Tenebrio molitor larvae. The EALE treatment was able to extend the average lifespan of the larvae (6.5 days) in comparison to S. aureus-infected larvae (1 day). Next, the samples were characterized by High-Performance Liquid Chromatography coupled to a mass spectrometer, allowing the identification of 11 substances, including seven flavonoids, substances whose antimicrobial activity is already well-reported in the literature. The number of bioactive compounds found in the chemical composition of H. balsamifera emphasizes its significance in both traditional medicine and scientific research that studies new treatments based on substances from the Brazilian flora.

Natural products targeting the synthesis of β(1,3)-D-glucan and chitin of the fungal cell wall. Existing drugs and recent findings

BACKGROUND

During the last three decades systemic fungal infections associated to immunosuppressive therapies have become a serious healthcare problem. Clinical development of new antifungals is an urgent requirement. Since fungal but not mammalian cells are encased in a carbohydrate-containing cell wall, which is required for the growth and viability of fungi, the inhibition of cell wall synthesizing machinery, such as β(1,3)-D-glucan synthases (GS) and chitin synthases (CS) that catalyze the synthesis of β(1-3)-D-glucan and chitin, respectively, represent an ideal mode of action of antifungal agents. Although the echinocandins anidulafungin, caspofungin and micafungin are clinically well-established GS inhibitors for the treatment of invasive fungal infections, much effort must still be made to identify inhibitors of other enzymes and processes involved in the synthesis of the fungal cell wall.

PURPOSE

Since natural products (NPs) have been the source of several antifungals in clinical use and also have provided important scaffolds for the development of semisynthetic analogues, this review was devoted to investigate the advances made to date in the discovery of NPs from plants that showed capacity of inhibiting cell wall synthesis targets. The chemical characterization, specific target, discovery process, along with the stage of development are provided here.

METHODS

An extensive systematic search for NPs against the cell wall was performed considering all the articles published until the end of 2020 through the following scientific databases: NCBI PubMed, Scopus and Google Scholar and using the combination of the terms "natural antifungals" and "plant extracts" with "fungal cell wall".

RESULTS

The first part of this review introduces the state of the art of the structure and biosynthesis of the fungal cell wall and considers exclusively those naturally produced GS antifungals that have given rise to both existing semisynthetic approved drugs and those derivatives currently in clinical trials. According to their chemical structure, natural GS inhibitors can be classified as 1) cyclic lipopeptides, 2) glycolipids and 3) acidic terpenoids. We also included nikkomycins and polyoxins, NPs that inhibit the CS, which have traditionally been considered good candidates for antifungal drug development but have finally been discarded after enduring unsuccessful clinical trials. Finally, the review focuses in the most recent findings about the growing field of plant-derived molecules and extracts that exhibit activity against the fungal cell wall. Thus, this search yielded sixteen articles, nine of which deal with pure compounds and seven with plant extracts or fractions with proven activity against the fungal cell wall. Regarding the mechanism of action, seven (44%) produced GS inhibition while five (31%) inhibited CS. Some of them (56%) interfered with other components of the cell wall. Most of the analyzed articles refer to tests carried out in vitro and therefore are in early stages of development.

CONCLUSION

This report delivers an overview about both existing natural antifungals targeting GS and CS activities and their mechanisms of action. It also presents recent discoveries on natural products that may be used as starting points for the development of potential selective and non-toxic antifungal drugs.

Antimicrobial, antioxidant activity and phytochemical prospection of Eugenia involucrata DC. leaf extracts

The species Eugenia involucrata DC. is a plant native to Brazil and is traditionally used for intestinal problems, however, little research has documented about its biological potential and phytochemical profile. Thus, the objective of this study was to carry out preliminary phytochemical prospecting, antimicrobial and antioxidant potential of E. involucrata extracts. Using the E. involucrata leaves, aqueous and organic extracts were obtained using the following solvents (ethanol, methanol, hexane, acetone, dichloromethane and ethyl acetate). The phytochemical prospecting detected the presence of saponins, steroids, flavonoids and tannins in the extracts. Ethanolic and methanolic extracts presented antimicrobial activity for most of the bacterial strains tested, as well as for yeast Candida albicans, with concentrations between 3.12 and 50 mg/mL. The ethanolic and metanolic extract presented high free radical sequestration potential (>90%). The methanol extract showed an IC50 value statistically equal to that found for the commercial antioxidant BHT (p <0.05). The crude extracts obtained with ethanol and methanol were the most promising. These results suggest that methanolic, ethanolic and aqueous extracts are a promising source of natural bioactive.

Antimicrobial Activities of Satureja khuzestanica Jamzad; A Review

Satureja khuzestanica Jamzad is a species native to Iran and is highly important in Southwestern regions. It belongs to the Lamiaceae family and grows in different climates. A number of pharmacological properties such as analgesic, anti-inflammatory, anticancer, anti-thyroid, antioxidant, and diuretic have been attributed to this plant. In recent years, a wide range of biological properties, extract, and essential oil of Satureja khuzestanica has been studied by researchers. In the present study, Scopus, SID, ISI, Google Scholar, and PubMed indices were used to extract research articles. No publication time constraint was considered, and the keyword "Satureja khuzestanica" was used to search articles. All extracted articles were examined by two expert researchers and those on the biologic and fundamental science properties of this plan entered the study. Results showed that S. khuzestanica has extensive research and medicinal applications. Considering the economic and medical importance of S. khuzestanica, it is hoped that more extensive studies can be conducted in the future on the use of compounds and derivatives of this plant in order to obtain herbal medications to treat pathogens in human and animal.

Interactions with Microbial Proteins Driving the Antibacterial Activity of Flavonoids

Flavonoids are among the most abundant natural bioactive compounds produced by plants. Many different activities have been reported for these secondary metabolites against numerous cells and systems. One of the most interesting is certainly the antimicrobial, which is stimulated through various molecular mechanisms. In fact, flavonoids are effective both in directly damaging the envelope of Gram-negative and Gram-positive bacteria but also by acting toward specific molecular targets essential for the survival of these microorganisms. The purpose of this paper is to present an overview of the most interesting results obtained in the research focused on the study of the interactions between flavonoids and bacterial proteins. Despite the great structural heterogeneity of these plant metabolites, it is interesting to observe that many flavonoids affect the same cellular pathways. Furthermore, it is evident that some of these compounds interact with more than one target, producing multiple effects. Taken together, the reported data demonstrate the great potential of flavonoids in developing innovative systems, which can help address the increasingly serious problem of antibiotic resistance.

Aucklandia lappa Causes Membrane Permeation of Candida albicans

Candida albicans is a major fungal pathogen in humans. In our previous study, we reported that an ethanol extract from Aucklandia lappa weakens C. albicans cell wall by inhibiting synthesis or assembly of both (1,3)-β-D-glucan polymers and chitin. In the current study, we found that the extract is involved in permeabilization of C. albicans cell membranes. While uptake of ethidium bromide (EtBr) was 3.0% in control cells, it increased to 7.4% for 30 min in the presence of the A. lappa ethanol extract at its minimal inhibitory concentration (MIC), 0.78 mg/ml, compared to uptake by heat-killed cells. Besides, leakage of DNA and proteins was observed in A. lappa-treated C. albicans cells. The increased uptake of EtBr and leakage of cellular materials suggest that A. lappa ethanol extract induced functional changes in C. albicans cell membranes. Incorporation of diphenylhexatriene (DPH) into membranes in the A. lappa-treated C. albicans cells at its MIC decreased to 84.8%, after 60 min of incubation, compared with that of the controls, indicate that there was a change in membrane dynamics. Moreover, the anticandidal effect of the A. lappa ethanol extract was enhanced at a growth temperature of 40°C compared to that at 35°C. The above data suggest that the antifungal activity of the A. lappa ethanol extract against C. albicans is associated with synergistic action of membrane permeabilization due to changes in membrane dynamics and cell wall damage caused by reduced formation of (1,3)-β-D-glucan and chitin.

Antimicrobial flavonoids as a potential substitute for overcoming antimicrobial resistance

BACKGROUND

Infectious diseases are the leading cause of death in 21^st century due to antimicrobial resistance and scarcity of new molecules to undertake rising infections. There could be a multiple reasons behind antimicrobial resistance whether it is increased drug metabolism or bacterial endotoxins. The demand of effective medication is increasing day by day to treat microbial infections and combat antimicrobial resistance. In recent years most of the synthetic antimicrobials developed resistance so natural products could provide better options to fulfill this demand. There has been increasing interest in the research on flavonoids because various flavonoids were found to be effective against pathogenic microorganisms.

OBJECTIVE

The objective of this article will be to explore antimicrobial activity of flavonoids with special focus on their possible mechanism of action.

METHODS

The article reviewed recent literature related to flavonoids with antimicrobial activity, which were isolated from various sources and the compounds showing fairly good activity against tested microbial species were discussed.

RESULTS

By throughout literature review it has been found that flavonoids show antimicrobial effect by inhibiting virulence factors, efflux pump, biofilm formation, membrane disruption, cell envelop synthesis, nucleic acid synthesis, and bacterial motility inhibition.

CONCLUSION

Most of the antimicrobial drugs available now a days are ineffective due to development of resistance to them. Flavonoids have the potential to overcome this emerging crisis as this class of natural products showed the antimicrobial activity by different mechanisms than those of conventional drugs, so flavonoid could be an effective treatment of pathogenic infections.

Aucklandia lappa Causes Cell Wall Damage in Candida albicans by Reducing Chitin and (1,3)-β-D-Glucan

The fungal cell wall is a major target of antifungals. In this study, we report the antifungal activity of an ethanol extract from Aucklandia lappa against Candida albicans. We found that the extract caused cell wall injury by decreasing chitin synthesis or assembly and (1,3)-β-D-glucan synthesis. A sorbitol protection assay demonstrated that the minimum inhibitory concentration (MIC) of the A. lappa extract against C. albicans cells increased eight-fold from 0.78 to 6.24 mg/ml in 72 h. Cell aggregates, which indicate damage to the cell wall or membrane, were commonly observed in the A. lappatreated C. albicans cells through microscopic analysis. In addition, the relative fluorescence intensities of the C. albicans cells incubated with the A. lappa extract for 3, 5, and 6 h were 92.1, 84.6, and 79.8%, respectively, compared to the controls, estimated by Calcofluor White binding assay. This result indicates that chitin content was reduced by the A. lappa treatment. Furthermore, synthesis of (1,3)-β-D-glucan polymers was inhibited to 84.3, 79.7, and 70.2% of that of the control treatment following incubation of C. albicans microsomes with the A. lappa extract at a final concentration equal to its MIC, 2× MIC, and 4× MIC, respectively. These findings suggest that the A. lappa ethanol extract may aid the development of a new antifungal to successfully control Candida-associated disease.

Flavonoids with antibacterial and antioxidant potentials from the stem bark of Uapaca heudelotti

Two flavonol glycosides; U1: naringenin-7-O-glucoside and U2: kaempferol-3-O-glucoside were isolated for the first time, from ethyl acetate fraction of the stem bark of a traditional medicinal plant called Uapaca heudelotti. IR and NMR spectroscopy were used to elucidate the structures of the isolated compound. The two compounds were active against the 7 tested microorganisms; Escherichia coli, Bacillus subtilis, Salmonella typhi, Streptococcus pyogenes, Klebsiella pneumoniae, Staphylococcus aureus and Proteus mirabilis. The zones of inhibition of the compounds ranged from 16 to 23 mm. The MIC value was as low as 6.25 μg/mL against Salmonella typhi, Streptococcus pyogenes, and Bacillus subtilis. The radical scavenging activity of compound U1 and U2 was 80 and 85 % at 240 μg/mL, while that of the standard drug was 98% at 240 μg/mL. The results show an existent possibility of using the plant for the treatment of microbial diseases.

Evaluation of antimicrobial activity of chondrillasterol isolated from Vernonia adoensis (Asteraceae)

BACKGROUND

Bacteria have developed resistance to most of the current antibiotics. There is evidence suggesting that plant-derived compounds have a potential for interacting with biological processes. One of the plants commonly used in African ethnomedicine is Vernonia adoensis from the Asteraceae family. The leaves of the plant have been reported to have antimicrobial activity. Hence, the aim of this study was to isolate the bioactive compounds from the leaf extract and evaluate their antibacterial activity on Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa. In addition, the effect of the isolated compound on biofilms of P. aeruginosa was determined.

METHODS

Isolation of phytochemicals from the leaves of V. adoensis was done using column chromatography. Preparative TLC was used to further isolate mixed compounds in the fractions. Nuclear magnetic resonance spectroscopy and mass spectrometry was used to identify the isolated pure compounds. The broth microdilution assay was carried out to evaluate the antibacterial activity of the isolated compound on P. aeruginosa, S. aureus and K. pneumoniae. Crystal violet staining technique was used to evaluate the effect of the isolated compound on biofilms of P. aeruginosa.

RESULTS

The compound isolated from V. adoensis was identified as chondrillasterol. Chondrillasterol exhibited 25, 38 and 65% inhibition of growth on S. aureus, K. pneumoniae and P. aeruginosa respectively. At 1.6 μg/mL chondrillasterol completely disrupted mature biofilm of P. aeruginosa while at 100 μg/mL the compound completely inhibited formation of biofilms of the bacteria.

CONCLUSION

Chondrillasterol isolated from V. adoensis has antibacterial properties against S. aureus, K. pneumoniae and P. aeruginosa. The compound also has biofilm inhibition and disruption activity against P. aeruginosa biofilms. Thus, the active phytochemical could be a useful template for the development of new antimicrobial agents with both antibacterial and antibiofilm activity.

Influence of Medicinal Plant Extracts on the Growth of Oral Pathogens Streptococcus Mutans and Lactobacillus Acidophilus: An In-Vitro Study

AIM:

This study investigated the antibacterial efficacy of five plant extracts, as well as the combinations of the two most effective plant, extracts either with or without commercial varnish (MI varnish) on the in vitro growth of Streptococcus mutans and Lactobacillus acidophilus in comparison to MI varnish using agar disk diffusion and broth dilution methods.

METHODS:

Methanolic extractions of five plants (Cinnamon, Turmeric, Ginger, Clove and Black seed,) were tested against the growth of the two oral pathogens. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for the two most effective extracts, and their combinations with different ratios were evaluated against the growth of the two oral pathogens, followed by incorporating the two effective plants or each into commercial MI varnish to be assessed against the oral pathogens in comparison to MI varnish.

RESULTS:

Only Cinnamon and Clove produced inhibition zones against Streptococcus mutans and Lactobacillus acidophilus growth. MIC for the two plants showed equal antimicrobial activity against Streptococcus mutans, while Cinnamon had a higher sensitivity to Lactobacillus acidophilus than Clove. A mixture of Cinnamon and Clove in a ratio 1:2 exhibited the highest antibacterial activity. Integration the mixture of both plants into MI varnish in a ratio of 1:1:1 presented the highest antibacterial activity. Meanwhile, the lowest one was recorded for the MI varnish alone.

CONCLUSION:

Methanolic extract of Cinnamon and Clove has considerable antimicrobial activity against Streptococcus mutans and Lactobacillus acidophilus and a new tool for minimally invasive and adhesive dentistry avenues.

Molecular insight into the therapeutic potential of phytoconstituents targeting protein conformation and their expression

BACKGROUND

Native protein conformation is essential for the functional activity of the proteins and enzymes. Defects in conformation or alterations in expression of the proteins have been reported in various diseases.

PURPOSE

The aim of this study is to review the molecular insight into the therapeutic potential of phytoconstituents targeting protein conformations or expressions.

METHODS

Published literatures were searched in PubMed, Scopus, Web of Science; Article published till Dec 2017 were extracted. The literature was assessed from the Central University of Rajasthan, India. Present study evaluate article based on the role of active plant constituents on the conformation and expression of the different proteins.

RESULTS

Plant components play their role either at the molecular level or cellular level and exhibit antibacterial, antiviral, anti-neurodegenerative and other activities. Plant active compounds isolated from different plants may either stabilize or destabilize the conformation of proteins or alter expression level of the protein involved in these diseases, therefore, can play a significant role in preventing diseases caused by the alteration in these proteins.

CONCLUSION

In the present article, we have reviewed the molecular mechanism of plant active compounds, their target proteins, methods of extraction and identification, and their biological significances. Therefore, a proper understanding of the effect of these herbal molecules on the concerned proteins may help to develop new herbal-based therapeutics for various diseases.

Wound Healing Activity of Plants from the Convolvulaceae Family

Significance: Compounds derived from plants are gaining importance for the treatment of several diseases. Many plants from the Convolvulaceae family contain compounds that have demonstrated wound healing and antidiabetic activity. Such compounds can be effectively used as a part of treatments to promote wound healing in diabetics and used in combination with antimicrobial therapy to reduce the likelihood of drug resistance and allergic reactions. Novel strategies for developing herbal formulations such as nanoparticles and adhesive patches can improve the delivery of plant-based therapeutic agents. Recent Advances: Studies have confirmed the antidiabetic and wound healing activities of Merremia tridentata, Argyreia speciosa, and Ipomoea batatas, whereas Evolvulus alsinoides, Evolvulus nummularius, Argyreia cuneata, and Ipomoea carnea have wound healing activity. Critical Issues: Drug resistance is a major problem associated with antimicrobial therapy and can affect wound healing processes. Phytoconstituents can facilitate healing processes and reduce reliance on antibiotics. Future Directions: Plants from the Convolvulaceae family have had frequent traditional uses, and all plants selected for this study have antimicrobial, antidiabetic, and wound healing properties. Detailed phytochemical studies of these plants can help develop novel wound healing therapies.

Polypyrrole/tannin biobased nanocomposite with enhanced electrochemical and physical properties

In this research, tannin (TA) extracted from Acacia mangium and a cationic surfactant, cetyltrimethylammonium bromide (CTAB), were used to modify and enhance the physical and electrochemical properties of a polypyrrole (PPy) composite. Brunauer–Emmett–Teller (BET) analysis presented a higher degree of surface area and porosity for the PPy/TA/CTAB nanocomposite. A highly porous and rod like structure with a lumpy surface was observed for PPy/TA prepared in the presence of CTAB by Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Cyclic voltammograms of the modified SPE electrode using PPy/TA/CTAB displayed an enhanced current response compared to the electrode modified with only PPy or PPy/TA. Electrochemical Impedance Spectroscopy (EIS) exhibited a lower value of charge transfer resistance (R_ct) and higher electron transfer for the modified electrode, making the nanocomposite a promising candidate for biosensor application.

Tannin (TA) extracted from Acacia mangium and a cationic surfactant, cetyltrimethylammonium bromide (CTAB), were used to modify and enhance the physical and electrochemical properties of polypyrrole (PPy) composite.

Lupinifolin from Albizia myriophylla wood: A study on its antibacterial mechanisms against cariogenic Streptococcus mutans

OBJECTIVE

To determine the anti-Streptococcus mutans mechanisms of action of lupinifolin from Albizia myriophylla Benth. (Fabaceae) wood and provide scientific evidence to support the traditional use of the plant against dental caries.

METHODS

The minimum inhibitory concentration (MIC) was evaluated using the broth micro-dilution method. The effects of lupinifolin on bactericidal activity, bacterial cell walls, and membranes were investigated by time-kill, lysis, and leakage assays, respectively. Electron microscopy was utilized to observe any cell morphological changes caused by the compound. Localization of lupinifolin in S. mutans was detected using the thin layer chromatography technique.

RESULTS

The MIC range of lupinifolin against S. mutans (n=6) was 2-4 μg/ml. This compound displayed bactericidal effects on S. mutans ATCC 25175 by 90-99.9% killing at 4MIC-16MIC after 8-24 hours. Lupinifolin-treated cells demonstrated no lysis. However, significant cytoplasmic leakage through the bacterial membrane was observed after treatment with lupinifolin at 4MIC-16MIC. As revealed by ultrastructural analysis, lupinifolin produced some changes in bacterial cell walls and membranes. Moreover, the compound was observed in the cytoplasmic fraction of the lupinifolin-treated cells. These results suggest that lupinifolin can enter the cell of bacteria but does not accumulate in the cell envelope and subsequently disrupts the integrity of the cytoplasmic membrane, leading to cell death.

CONCLUSION

The scientific evidence from this study offers valuable insights into the potential role of lupinifolin in pharmaceutical and antibiotic applications and supports the therapeutic effects of A. myriophylla, which has traditionally been used as an alternative treatment for dental caries.

Antimicrobial activity of different sodium and potassium salts of carboxylic acid against some common foodborne pathogens and spoilage-associated bacteria

Cleaning and disinfection represent the most important activities associated with the elimination of dirt and microorganisms at food processing plants. Improper procedures may lead to cross contamination of food leading to its spoilage or even the transmission of foodborne pathogens. Several strategies have been used in order to achieve a good disinfection of surfaces and products; nevertheless, microbial resistance to common-use-products has developed lately. Due to this fact, the development of new non-toxic-food compatible chemical agents that reduce the impact of foodborne pathogens and spoilage causing microorganisms is desirable for the food industry. The objective of the present study was to evaluate the antimicrobial activity of different sodium and potassium salts of aliphatic and aromatic carboxylic acid on the growth of common food spoilage and pathogenic microorganisms. Growth curves were determined for Leuconostoc mesenteroides, Lactobacillus plantarum, Enterococcus faecalis, Candida albicans, Pseudomonas aeruginosa, Salmonella Enteritidis, and Listeria monocytogenes in contact with different concentrations of carboxylic acid salts. The inhibitory effect of both aliphatic and aromatic carboxylic acid salts, in accordance with concentration levels, was 100>50>25mg/ml. The inhibitory effect of aliphatic salts was butanoic>hexanoic> octanoic>decanoic and, benzoic>gallic>caffeic acid salts for aromatic salts. In general, sodium salts were more inhibitory than potassium salts (p≤0.05).

Inhibition of biofilm formation in Mycobacterium smegmatis by Parinari curatellifolia leaf extracts

Background

Tuberculosis (TB) is a serious public health problem worldwide. Mycobacterium tuberculosis (M. tuberculosis) grows as drug tolerant pellicles. Agents that inhibit biofilm formation in M. tuberculosis have the potential to reduce the disease treatment period and improve the quality of tuberculosis chemotherapy. Parinari curatellifolia (P. curatellifolia) leaf extracts are claimed to treat symptoms similar to tuberculosis in ethnomedicinal practices. Mycobacterium smegmatis (M. smegmatis) is a surrogate organism used in antimycobacterial drug discovery assays. In this study, the effect of the leaf extracts of P. curatellifolia on M. smegmatis growth and biofilm formation was investigated in order to determine the basis of its use in traditional medicinal use.

Methods

Phytochemicals from P. curatellifolia leaves were prepared using a mixture of 50% dichloromethane (DCM): 50% methanol and by serial exhaustive extraction using different solvents of decreasing polarity. The solvents were used in the following order, hexane > dichloromethane > ethyl acetate > acetone >ethanol > methanol > water. The micro-broth dilution method was used as an antimycobacterial susceptibility test to screen for the extract that effectively inhibited M. smegmatis growth and biofilm formation. Biofilm quantification was performed by staining the biofilms with crystal violet and determining the amount of the stain using a spectrophotometer. In addition, the effects of combining the most active extract with kanamycin were also investigated.

Results

The minimum inhibitory concentrations (MIC) of the extracts were found to be 6.2 μg/ml for the acetone extract, 12.5 μg/ml for both the ethanol and the total extract and 50 μg/ml for both the methanol and ethyl acetate extracts. The ethanol extract, dichloromethane extract and water extract were the only extracts that effectively inhibited biofilm formation in M. smegmatis. Combining the ethanol extract with kanamycin enhanced the effect of the ethanol extract in terms of inhibition of biofilm formation.

Conclusions

P. curatellifolia leaves contain phytochemicals that have the potential to be used both as antimycobacterial and anti-biofilm formation compounds.

Examination of Endogenous Peptides in Medicago truncatula Using Mass Spectrometry Imaging

Plant science is an important, rapidly developing area of study. Within plant science, one area of study that has grown tremendously with recent technological advances, such as mass spectrometry, is the field of plant-omics; however, plant peptidomics is relatively underdeveloped in comparison with proteomics and metabolomics. Endogenous plant peptides can act as signaling molecules and have been shown to affect cell division, development, nodulation, reproduction, symbiotic associations, and defense reactions. There is a growing need to uncover the role of endogenous peptides on a molecular level. Mass spectrometric imaging (MSI) is a valuable tool for biological analyses as it allows for the detection of thousands of analytes in a single experiment and also displays spatial information for the detected analytes. Despite the prediction of a large number of plant peptides, their detection and imaging with spatial localization and chemical specificity is currently lacking. Here we analyzed the endogenous peptides and proteins in Medicago truncatula using matrix-assisted laser desorption/ionization (MALDI)-MSI. Hundreds of endogenous peptides and protein fragments were imaged, with interesting peptide spatial distribution changes observed between plants in different developmental stages.

In vitro antimicrobial activity of five essential oils on multidrug resistant Gram-negative clinical isolates

Aim/Background:

The emergence of drug-resistant pathogens has drawn attention on medicinal plants for potential antimicrobial properties. The objective of the present study was the investigation of the antimicrobial activity of five plant essential oils on multidrug resistant Gram-negative bacteria.

Materials and Methods:

Basil, chamomile blue, origanum, thyme, and tea tree oil were tested against clinical isolates of Acinetobacter baumannii (n = 6), Escherichia coli (n = 4), Klebsiella pneumoniae (n = 7), and Pseudomonas aeruginosa (n = 5) using the broth macrodilution method.

Results:

The tested essential oils produced variable antibacterial effect, while Chamomile blue oil demonstrated no antibacterial activity. Origanum, Thyme, and Basil oils were ineffective on P. aeruginosa isolates. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration values ranged from 0.12% to 1.50% (v/v) for tea tree oil, 0.25-4% (v/v) for origanum and thyme oil, 0.50% to >4% for basil oil and >4% for chamomile blue oil. Compared to literature data on reference strains, the reported MIC values were different by 2SD, denoting less successful antimicrobial activity against multidrug resistant isolates.

Conclusions:

The antimicrobial activities of the essential oils are influenced by the strain origin (wild, reference, drug sensitive, or resistant) and it should be taken into consideration whenever investigating the plants’ potential for developing new antimicrobials.

Inhibition of Helicobacter pylori growth and its colonization factors by Parthenium hysterophorus extracts

ETHNOPHARMACOLOGICAL RELEVANCE

Parthenium hysterophorus (Asteraceae) is a traditional medicinal plant used to treat gastrointestinal disorders, such as gastritis. Helicobacter pylori have been described as the etiological agent of gastritis, peptic ulcer, as well as gastric adenocarcinoma. 50% of the world's population is infected with this bacterium and the current therapy fails due to the increment in antibiotic resistance; therefore, it is necessary to find new approaches to control H. pylori infection, either by its eradication or by preventing the bacterial colonization.

AIM OF THE STUDY

To investigate the effect of P. hysterophorus extracts on H. pylori growth and upon its colonization-related factors.

MATERIALS AND METHODS

Five different polarity extracts from roots and aerial parts of P. hysterophorus were evaluated in vitro against H. pylori growth by the broth dilution method. Anti-colonization activities were determined as follows: motility in soft agar plates, urease activity by ammonia colorimetrical quantification, and adherence of FITC labeled H. pylori to AGS cells by fluorometrical measurement.

RESULTS

Organic extracts inhibited H. pylori growth. Particularly, the dichloromethane extract from roots showed a MIC of 15.6 µg/ml while the aqueous extracts showed low or null activity. There is a direct correlation between antibacterial activity and inhibition of motility. Urease activity was partially inhibited by organic extracts, at best 46%, except for the roots dichloromethane extract which reached 74% of inhibition with 500 µg/ml (IC50=136.4 µg/ml). Plant extracts inhibited adherence in different ranges but the dichloromethane-methanol ones possessed the highest effect, with a 70% maximal inhibition at 1mg/ml.

CONCLUSION

The results indicate that some P. hysterophorus extracts have various biological activities that could act synergistically against H. pylori. This work contributes to the ethnomedical knowledge of this species and underlines the potential of some organic extracts as a good source for the isolation of bioactive compounds.

Antibacterial and antiviral evaluation of sulfonoquinovosyldiacylglyceride: a glycolipid isolated from Azadirachta indica leaves

Assessment of antibacterial as well as antiherpes virus activity of sulfonoquinovosyldiacylglyceride (SQDG), a glycolipid, isolated from the leaves of Azadirachta indica has been described. Antimicrobial activity was evaluated against Gram-positive, Gram-negative bacteria and herpes simplex virus. SQDG showed significant inhibitory activity against Salmonella typhi and two isolates of Shigella dysenteriae with MIC values 32 μg ml(-1) , while three isolates of Salm. typhi, Escherichia coli and Vibrio cholerae were inhibited at 64 μg ml(-1) and have shown zone diameter ranging from 6.2 to 12.3 mm. The growth kinetics study of SQDG on Salm. typhi and Sh. dysenteriae revealed that the growths were completely inhibited at their MIC values within 24 h of exposure. Interestingly, SQDG inhibits herpes simplex virus (HSV) type 1 and 2 with the EC50 of 9.1 and 8.5 μg ml(-1) , compared with acyclovir (2.2 and 2.8 μg ml(-1) against HSV-1 and HSV-2). The selectivity index (SI) was found to be 12.4 against HSV-1 and 13.41 with HSV-2. Furthermore, the expression of proinflammatory cytokines of HSV-infected and SQDG-treated macrophages using ELISA kit revealed that SQDG significantly downregulated the production of TNF-α, IL-1β, IL-12 and IL-6.

SIGNIFICANCE AND IMPACT OF THE STUDY

The water-soluble metabolite sulfonoquinovosyldiacylglyceride (SQDG) isolated from Azadirachta indica (Neem) possess significant antibacterial as well as anti-HSV activity. The efficacies as well as the solubility factor of SQDG substantiate a greater attention for its use as phytotherapeutic drug for controlling microbial infections as most consumers have better acceptance of phytomedicines than synthetic drugs.

Snake venom PLA2s inhibitors isolated from Brazilian plants: synthetic and natural molecules

Ophidian envenomation is an important health problem in Brazil and other South American countries. In folk medicine, especially in developing countries, several vegetal species are employed for the treatment of snakebites in communities that lack prompt access to serum therapy. However, the identification and characterization of the effects of several new plants or their isolated compounds, which are able to inhibit the activities of snake venom, are extremely important and such studies are imperative. Snake venom contains several organic and inorganic compounds; phospholipases A₂ (PLA₂s) are one of the principal toxic components of venom. PLA₂s display a wide variety of pharmacological activities, such as neurotoxicity, myotoxicity, cardiotoxicity, anticoagulant, hemorrhagic, and edema-inducing effects. PLA₂ inhibition is of pharmacological and therapeutic interests as these enzymes are involved in several inflammatory diseases. This review describes the results of several studies of plant extracts and their isolated active principles, when used against crude snake venoms or their toxic fractions. Isolated inhibitors, such as steroids, terpenoids, and phenolic compounds, are able to inhibit PLA₂s from different snake venoms. The design of specific inhibitors of PLA₂s might help in the development of new pharmaceutical drugs, more specific antivenom, or even as alternative approaches for treating snakebites.

Oxalis corniculata (Oxalidaceae) leaf extract exerts in vitro antimicrobial and in vivo anticolonizing activities against Shigella dysenteriae 1 (NT4907) and Shigella flexneri 2a (2457T) in induced diarrhea in suckling mice

In this study, the extract of a green leafy vegetable Oxalis corniculata (Oxalidaceae) was evaluated for its in vitro antibacterial and in vivo anti colonizing effect against common intestinal pathogenic bacteria. Methanolic extract (80%) of Oxalis corniculata (Oxalidaceae) leaf contained a polyphenol content of 910 mg gallic acid equivalent per gram of dry weight and the yield was 8%. The flavonoid content was 2.353 g quercetin equivalent per 100 g of the extract. In vitro studies indicated that the extract inhibited numerous pathogenic bacteria like Staphylococcus aureus (ATCC 25922), Escherichia coli (ATCC 25923), Shigella dysenteriae 1 (NT4907), Shigella flexneri 2a (2457T), Shigella boydii 4 (BCH612), and Shigella sonnie phase I (IDH00968). The minimum inhibitory concentration (MIC) against E. coli (ATCC 25923) was minimal (0.08 mg/mL), whereas MIC against S. flexneri 2a (2457T) was higher (0.13 mg/mL). A suckling mouse model was developed which involved challenging the mice intragastrically with S. flexneri 2a (2457T) and S. dysenteriae 1 (NT4907) to study the anticolonization activity. It was revealed that the extract was more potent against S. dysenteriae 1 (NT4907) as compared to S. flexneri 2a (2457T). It was also found that simultaneous administration of extract along with bacterial inoculums promoted good anticolonization activity. Significant activity was observed even when treated after 3 h of bacterial inoculation.