Antimicrobial activity of the crude extracts and compounds from Ficus chlamydocarpa and Ficus cordata (Moraceae)

A metabolomics approach for the evaluation of Ficus benghalensis female in vivo reproductive effects relative to its metabolite fingerprint as determined via UPLC-MS and GC-MS

ETHNOPHARMACOLOGICAL RELEVANCE

Ficus benghalensis, commonly known as Banyan Fig, is the national tree of India and its aerial roots are used traditionally to treat female reproductive disorders. However, despite this traditional use, no pharmacological evidence could be traced supporting this use. Additionally, no comprehensive metabolite profiling was reported for F. benghalensis aerial roots.

AIM OF THE STUDY

This study attempts to justify biochemically the traditional use of F. benghalensis aerial roots in treatment of female reproductive disorders and in relation to its secondary metabolite profile.

MATERIALS AND METHODS

Total ethanol extract (TEE) and subfractions [petroleum ether (PEF), chloroform (CHF), ethyl acetate (EAF) and n-butanol (BUF] were prepared from air-dried powdered aerial roots of F. benghalensis. Detailed in-vivo investigation of the hormonal activity and action mechanism of the total ethanol extract and subfractions was carried out through evaluation of estrogenic and gonadotropic activities. The estrogenic activity was evaluated on ovariectomized immature female rats through estimating uterine weight, vaginal cornification and serum estradiol level along with histological examination of uteri. The gonadotropic activity was measured by assay of follicle stimulating hormone (FSH) and luteinizing hormone (LH) like activities. Total follicular and corpora lutea counts in immature female rats were used to determine FSH and LH like activities, respectively in addition to histological picture of the genitalia. Comprehensive non-targeted metabolite profiling was carried out for the TEE and subfractions using UPLC-HRMS in negative and positive ionization modes. UPLC-MS fingerprint was subjected to principal component analysis (PCA) and partial least squares analyses to correlate the bioactivities to specific chemical constituents in F. benghalensis different subfractions. GC-MS was further used for non-polar silylated fractions.

RESULTS

Results revealed that only the non-polar PEF and CHF displayed moderate estrogenic and FSH-like activities but with no LH-like activity. Metabolites profiling via (UPLC-HRMS) and multivariate PCA analysis enabled identification and comparison of various chemical classes in F. benghalensis extract and fractions. The active non-polar fractions revealed nearly similar metabolites profile being composed of isoflavonoids, triterpenes, sterols, fatty acids and cyclic peptides. In contrast, polar fractions were more abundant in apocarotenoids, fatty acyl amides, hydroxybenzoates and hydroxycinnamates in addition to two lignans. PLS analysis revealed strong correlation between hydroxylated fatty acids and pyranoisoflavones with estrogenic and FSH-like activities. GC-MS analysis was further employed for non-polar fractions profiling revealing for their enrichment in fatty acids/esters, terpenes, organic acids and phenolics.

CONCLUSION

This is the first study to rationalize the use of F. benghalensis aerial root traditionally in treatment of gynecological disorders, revealing that the petroleum ether and chloroform non-polar subfractions of F. benghalensis showed estrogenic and FSH-like activity with absence of LH-like activity. This biological activity could possibly be attributed to its metabolites profile of isoflavonoids, fatty acids, triterpenes, sterols and cyclic peptides identified via UPLC-MS and GC-MS techniques. Consequently, F. benghalensis aerial roots should be used with caution in traditional treatment of female infertility or other reproductive disorders.

Comparative LC-MS/MS-based molecular networking, DNA fingerprinting, and in vitro anti-Helicobacter pylori activity of three Egyptian Ficus cultivars

Ficus species (Moraceae) have been used for nutrition and traditional medicine, and plants from this family are phytochemically abundant and serve as a potential source of natural products. As a result of the inherent complexity of the plant metabolomes and the fact that these Ficus species chemical space has not yet been fully decoded, it is still difficult to characterize their phytochemistry. Therefore, this study, we suggest the use of the molecular networking to elucidate the chemical classes existing in leaves of three Ficus species (F. deltoidei Jack, F. drupacea Thunb and F. sycomorus L.) and highlight the importance of molecular networking in examining their chemotaxonomy . By using computational tools, 90 metabolites were annotated , including phenolic acids, flavonoids, furanocoumarins, fatty acids and terpenoids. Phenolic acids were detected as the main class present in the three studied species. Flavonoids-C-glycosides, flavonoids-O-glycosides and isoflavonoids were mainly present in F. drupacea and F. sycomorus, while furanocoumarins were proposed in F. sycomorus. Vomifoliol-based sesquiterpenes were proposed in F. deltoidei. The chemotaxonomic differentiation agreed with the DNA fingerprinting using SCOT and ISSR markers. F. deltoidei, in particular, had a divergent chemical fingerprint as well as a different genotype. Chemotype differentiation using chemical fingerprints, in conjunction with the proposed genetic markers, creates an effective identification tool for the quality control of the raw materials and products derived from those three Ficus species. As well, F. drupacea exploited the most potent inhibition of H. pylori with MIC of 7.81 µg/ mL compared with clarithromycin. Overall, molecular networking provides a promising approach for the exploration of the chemical space of plant metabolomes and the elucidation of chemotaxonomy.

Comparative analysis of antimicrobial compounds from endophytic Buergenerula spartinae from orchid

A rare fungal endophyte, identified as Buergenerula spartinae (C28), was isolated from the roots of Cymbidium orchids and was characterised and evaluated for its antimicrobial activities. Bio-guided fractionation revealed 4 fractions from B. spartinae (C28) having antibacterial activities against at least one bacterial pathogen tested (Bacillus cereus and Staphylococcus aureus). However, inhibitory activities were absent against pathogenic fungi (Ganoderma boninense, Pythium ultimum and Fusarium solani). Fraction 2 and fraction 4 of B. spartinae (C28) exhibited potent antibacterial activities against S. aureus (MIC: 0.078 mg/mL) and B. cereus (MIC: 0.313 mg/mL), respectively. LCMS analysis revealed the presence of antibacterial agents and antibiotics in fraction 2 (benoxinate, pyropheophorbide A, (-)-ormosanine and N-undecylbenzenesulfonic acid) and fraction 4 (kaempferol 3-p-coumarate, 6-methoxy naphthalene acetic acid, levofuraltadone, hinokitiol glucoside, 3-α(S)-strictosidine, pyropheophorbide A, 5'-hydroxystreptomycin, kanzonol N and 3-butylidene-7-hydroxyphthalide), which may be responsible for the antibacterial activities observed. Most of the bioactive compounds profiled from the antibacterial fractions were discovered for the first time from endophytic isolates (i.e. from B. spartinae (C28)). Buergenerula spartinae (C28) from Cymbidium sp. is therefore, an untapped resource of bioactive compounds for potential applications in healthcare and commercial industries.

Ethnopharmacological Potential of Phytochemicals and Phytogenic Products against Human RNA Viral Diseases as Preventive Therapeutics

RNA viruses have been the most destructive due to their transmissibility and lack of control measures. Developments of vaccines for RNA viruses are very tough or almost impossible as viruses are highly mutable. For the last few decades, most of the epidemic and pandemic viral diseases have wreaked huge devastation with innumerable fatalities. To combat this threat to mankind, plant-derived novel antiviral products may contribute as reliable alternatives. They are assumed to be nontoxic, less hazardous, and safe compounds that have been in uses in the beginning of human civilization. In this growing COVID-19 pandemic, the present review amalgamates and depicts the role of various plant products in curing viral diseases in humans.

In Vivo and In Silico Analgesic Activity of Ficus populifolia Extract Containing 2-O-β-D-(3',4',6'-Tri-acetyl)-glucopyranosyl-3-methyl Pentanoic Acid

Natural product-based structural templates have immensely shaped small molecule drug discovery, and new biogenic natural products have randomly provided the leads and molecular targets in anti-analgesic activity spheres. Pain relief achieved through opiates and non-steroidal anti-inflammatory drugs (NSAIDs) has been under constant scrutiny owing to their tolerance, dependency, and other organs toxicities and tissue damage, including harm to the gastrointestinal tract (GIT) and renal tissues. A new, 3',4',6'-triacetylated-glucoside, 2-O-β-D-(3',4',6'-tri-acetyl)-glucopyranosyl-3-methyl pentanoic acid was obtained from Ficus populifolia, and characterized through a detailed NMR spectroscopic analysis, i.e., ¹H-NMR, ¹³C-DEPT-135, and the 2D nuclear magnetic resonance (NMR) correlations. The product was in silico investigated for its analgesic prowess, COX-2 binding feasibility and scores, drug likeliness, ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties, possible biosystem's toxicity using the Discovery Studio^®, and other molecular studies computational software programs. The glycosidic product showed strong potential as an analgesic agent. However, an in vivo evaluation, though at strong levels of pain-relieving action, was estimated on the compound's extract owing to the quantity and yield issues of the glycosidic product. Nonetheless, the F. populifolia extract showed the analgesic potency in eight-week-old male mice on day seven of the administration of the extract's dose in acetic acid-induced writhing and hot-plate methods. Acetic acid-induced abdominal writhing for all the treated groups decreased significantly (p < 0.0001), as compared to the control group (n = 6) by 62.9%, 67.9%, and 70.9% of a dose of 100 mg/kg (n = 6), 200 mg/kg (n = 6), and 400 mg/kg (n = 6), respectively. Similarly, using the analgesia meter, the reaction time to pain sensation increased significantly (p < 0.0001), as compared to the control (n = 6). The findings indicated peripheral and central-nervous-system-mediated analgesic action of the product obtained from the corresponding extract.

Characterization and Isolation of the Major Biologically Active Metabolites Isolated from Ficus retusa and Their Synergistic Effect with Tetracycline against Certain Pathogenic-Resistant Bacteria

Globally, pathogenic microbes have reached a worrisome level of antibiotic resistance. Our work aims to identify and isolate the active components from the bioactive Ficus retusa bark extract and assess the potential synergistic activity of the most major compounds' constituents with the antibiotic tetracycline against certain pathogenic bacterial strains. The phytochemical screening of an acetone extract of F. retusa bark using column chromatography led to the identification of 10 phenolic components. The synergistic interaction of catechin and chlorogenic acid as the most major compounds with tetracycline was evaluated by checkerboard assay followed by time-kill assay, against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, and Salmonella typhi with fraction inhibitory concentration index values (FICI) of 0.38, 0.43, 0.38, 0.38, 0.38, and 0.75 for catechin and 0.38, 0.65, 0.38, 0.63, 0.38, and 0.75 for chlorogenic acid. The combination of catechin and chlorogenic acid with tetracycline significantly enhanced antibacterial action against gram-positive and gram-negative microorganisms; therefore, catechin and chlorogenic acid combinations with tetracycline could be employed as innovative and safe antibiotics to combat microbial resistance.

Chemical constituents from Ficus sur Forssk (Moraceae)

Phytochemical investigation of the aerial roots of Ficus sur, a Cameroonian medicinal plant, resulted in a previously undescribed cerebroside, suroside (1), in addition to its aglycon congener suramide (2). Moreover, six known natural products including alpinumisoflavone (3), wighteone metabolite (4), oleanolic acid (5), β-sitosterol (6), β-sitosterol-3-O-β-D-glucopyranoside (7), and epi-ѱ-taraxastanolone (8) were identified. The structures of the previously undescribed compounds were determined by analysis of 1D and 2D-NMR (One and two dimensional nuclear magnetic resonance), mass spectrometry, chemical conversion, and by comparison of these data with those from the literature. Wighteone metabolite (4) exhibited a weak cytotoxic activity against the human HepG2 hepatocellular carcinoma cells with an IC50 value of 51.9 µM.

Promising Antimycobacterial Activities of Flavonoids against Mycobacterium sp. Drug Targets: A Comprehensive Review

Tuberculosis (TB) caused by the bacterial pathogen Mycobacterium tuberculosis (Mtb) remains a threat to mankind, with over a billion of deaths in the last two centuries. Recent advancements in science have contributed to an understanding of Mtb pathogenesis and developed effective control tools, including effective drugs to control the global pandemic. However, the emergence of drug resistant Mtb strains has seriously affected the TB eradication program around the world. There is, therefore, an urgent need to develop new drugs for TB treatment, which has grown researchers’ interest in small molecule-based drug designing and development. The small molecules-based treatments hold significant potential to overcome drug resistance and even provide opportunities for multimodal therapy. In this context, various natural and synthetic flavonoids were reported for the effective treatment of TB. In this review, we have summarized the recent advancement in the understanding of Mtb pathogenesis and the importance of both natural and synthetic flavonoids against Mtb infection studied using in vitro and in silico methods. We have also included flavonoids that are able to inhibit the growth of non-tubercular mycobacterial organisms. Hence, understanding the therapeutic properties of flavonoids can be useful for the future treatment of TB.

Multifunctional roles and pharmacological potential of β-sitosterol: Emerging evidence toward clinical applications

Currently, available therapeutic medications are both costly as well as not entirely promising in terms of potency. So, new candidates from natural resources are of research interest to find new alternative therapeutics. A well-known combination is a β-sitosterol, a plant-derived nutrient with anticancer properties against breast, prostate, colon, lung, stomach, and leukemia. Studies have shown that β-sitosterol interferes with multiple cell signaling pathways, including cell cycle, apoptosis, proliferation, survival, invasion, angiogenesis, metastasis, anti-inflammatory, anticancer, hepatoprotective, antioxidant, cardioprotective, and antidiabetic effects have been discovered during pharmacological screening without significant toxicity. The pharmacokinetic profile of β-sitosterol has also been extensively investigated. However, a comprehensive review of the pharmacology, phytochemistry and analytical methods of β-sitosterol is desired. Because β-sitosterol is a significant component of most plant materials, humans use it for various reasons, and numerous β-sitosterol-containing products have been commercialized. To offset the low efficacy of β-sitosterol, designing β-sitosterol delivery for "cancer cell-specific" therapy holds great potential. Delivery of β-sitosterol via liposomes is a demonstration that has shown great promise. But further research has not progressed on the drug delivery of β-sitosterol or how it can enhance β-sitosterol mediated anti-inflammatory activity, thus making β-sitosterol an orphan nutraceutical. Therefore, extensive research on β-sitosterol as an anticancer nutraceutical is recommended.

Specialized Metabolites from the Allelopathic Plant Retama raetam as Potential Biopesticides

To cope with the rising food demand, modern agriculture practices are based on the indiscriminate use of agrochemicals. Although this strategy leads to a temporary solution, it also severely damages the environment, representing a risk to human health. A sustainable alternative to agrochemicals is the use of plant metabolites and plant-based pesticides, known to have minimal environmental impact compared to synthetic pesticides. Retama raetam is a shrub growing in Algeria’s desert areas, where it is commonly used in traditional medicine because of its antiseptic and antipyretic properties. Furthermore, its allelopathic features can be exploited to effectively control phytopathogens in the agricultural field. In this study, six compounds belonging to isoflavones and flavones subgroups have been isolated from the R. raetam dichloromethane extract and identified using spectroscopic and optical methods as alpinumisoflavone, hydroxyalpinumisoflavone, laburnetin, licoflavone C, retamasin B, and ephedroidin. Their antifungal activity was evaluated against the fungal phytopathogen Stemphylium vesicarium using a growth inhibition bioassay on PDA plates. Interestingly, the flavonoid laburnetin, the most active metabolite, displayed an inhibitory activity comparable to that exerted by the synthetic fungicide pentachloronitrobenzene, in a ten-fold lower concentration. The allelopathic activity of R. raetam metabolites against parasitic weeds was also investigated using two independent parasitic weed bioassays to discover potential activities on either suicidal stimulation or radicle growth inhibition of broomrapes. In this latter bioassay, ephedroidin strongly inhibited the growth of Orobanche cumana radicles and, therefore, can be proposed as a natural herbicide.

LC-HRMS Profiling and Antidiabetic, Antioxidant, and Antibacterial Activities of Acacia catechu (L.f.) Willd

Acacia catechu (L.f.) Willd is a profoundly used traditional medicinal plant in Asia. Previous studies conducted in this plant are more confined to extract level. Even though bioassay-based studies indicated the true therapeutic potential of this plant, compound annotation was not performed extensively. This research is aimed at assessing the bioactivity of different solvent extracts of the plant followed by annotation of its phytoconstituents. Liquid chromatography equipped with high resolution mass spectrometry (LC-HRMS) is deployed for the identification of secondary metabolites in various crude extracts. On activity level, its ethanolic extract showed the highest inhibition towards α-amylase and α-glucosidase with an IC₅₀ of 67.8 ± 1 μg/mL and 10.3 ± 0.1 μg/mL respectively, inspected through the substrate-based method. On the other hand, the plant extract showed an antioxidant activity of 23.76 ± 1.57 μg/mL, measured through radical scavenging activity. Similarly, ethyl acetate and aqueous extracts of A. catechu showed significant inhibition against Staphylococcus aureus with a zone of inhibition (ZoI) of 13 and 14 mm, respectively. With the LC-HRMS-based dereplication strategy, we have identified 28 secondary metabolites belonging to flavonoid and phenolic categories. Identification of these metabolites from A. catechu and its biological implication also support the community-based usage of this plant and its medicinal value.

Therapeutic Potential of Genus Pongamia and Derris: Phytochemical and Bioactivity

Genus Pongamia and Derris belong to the Leguminosae family and are reported synonymously in literature. Although many compounds have been isolated from different plant parts but seed oil is known to produce non-edible medicinally important furanoflavonoids. The seed oil, commonly known as Karanj oil in Ayurvedic and Siddha traditional systems of medicine, is reported for the treatment of various skin infections and psoriasis. Several phytopharmacological investigations have proved the medicinal potential of furanoflavonoids in the skin and other disorders. Not only furanoflavonoids but several other important phenolic constituents such as chalcones, dibenzoylmethanes, aurones, isoflavones, flavanone dihydroflavonol, flavans, pterocarpans, rotenoids, coumarins, coumestans, stilbenoids and peltygynoids and their glycosides have been reported for different biological activities including antihyperglycemic, anti-inflammatory, anticancer, insecticidal, anti-alzheimer's, gastro protective, antifungal, antibacterial, etc. In the present review, the phytochemistry and pharmacological activities of the genera Pongamia and Derris have been summarized.

Bark extract of Cassia sieberiana DC. (Caesalpiniaceae) displayed good antibacterial activity against MDR gram-negative phenotypes in the presence of phenylalanine-arginine β-naphthylamide

BACKGROUND

Multidrug-resistant (MDR) bacteria remain a major cause of morbidity and mortality globally. The present study was designed to investigate the in vitro antibacterial activities of crude methanol extract and constituents isolated by Column Chromatography (CC) from Cassia sieberiana bark (CSB) against ten MDR Gram-negative bacteria, as well as the mechanisms of action of the most active sample.

METHODS

The antibacterial activity of the tested samples (extract, the fractions and their compounds isolated by CC and the structures obtained by exploiting ¹H and ¹³C Nuclear magnetic resonance (NMR) spectra) in the presence and absence of an efflux pumps inhibitor, phenylalanine-arginine β-naphthylamide (PAβN), was evaluated using the micro-dilution method. The effects of the most active sample were evaluated on the cell growth kinetic and on the bacterial H⁺-ATPase proton pumps.

RESULTS

Phytochemical composition of the crude extract showed a rather selective distribution of secondary metabolites (presence of polyphenols, tannins, steroids, triterpenes, flavonoids, alkaloids, saponins and absence of anthocyanins, anthraquinones). The tested samples displayed different antibacterial activities with minimal inhibitory concentrations (MICs) ranging from 64 to 512 μg/mL. Crude extract (CS) and fraction CSc showed the highest inhibitory spectra, both inhibiting all of the studied bacteria except Enterobacter aerogenes EA27 strain. Fraction CSc exerted bactericidal effects on most bacteria meanwhile, crude extract (CS) and sub-fraction CSc2 exerted bacteriostatic effects. Compounds 1 (spectaline) and 2 (iso-6-cassine) inhibited the growth of 70% (Escherichia coli ATCC8739 and AG102, Klebsiella pneumoniae ATCC11296, Enterobacter aerogenes ATCC13048 and EA27, Providencia stuartii ATCC29916, Pseudomonas aeruginosa PA01) and 60% (Escherichia coli ATCC8739, Klebsiella pneumoniae ATCC11296 and KP55, Providencia stuartii ATCC29916, Pseudomonas aeruginosa PA01 and PA124) of bacteria respectively with MICs ranging from 128 to 512 μg/mL. In the presence of PAβN, the activities of crude extract CS, fraction CAc and sub-fraction CSc2 strongly increased on most bacteria strains as their MICs significantly decreased. Sub-fraction CSc2 inhibited the H⁺-ATPase proton pumps and altered growth kinetic of Escherichia coli ATCC8739.

CONCLUSION

The overall results justify the traditional use of C. sieberiana for the treatment of bacterial infections.

Larvicidal and antibacterial activity of aqueous leaf extract of Peepal (Ficus religiosa) synthesized nanoparticles

In this study, the zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) were synthesized using the aqueous leaf extract of Ficus religiosa (Peepal tree). The synthesized nanoparticles were tested as larvicides against the larvae of Anopheles stephensi. Further, the synthesized nanoparticles were tested as antibacterial agents against the Escherichia coli (gram negative) and Staphylococcus aureus (gram positive) bacteria. The synthesized nanoparticles were characterized with UV-visible spectroscopy, X-rays powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The larvicidal mortality was observed after 24 h and 48 h by probit analysis. The antibacterial activity was evaluated using the well diffusion method. The synthesized nanoparticles were irregular shape and varied size. The larvae of An. stephensi were found highly susceptible against the ZnO NPs than the TiO2 NPs and aqueous leaves extract. The highest mortality was observed in synthesized ZnO NPs against first to third instars of (LC50 50, 75, and 5 ppm) and 100% mortality in fourth instars of An. stephensi. The higher zone of inhibition was occurred against the E. coli. This report of present investigation revealed that the rapid biological synthesis of ZnO NPs and TiO2 NPs using aqueous leaf extract of F. religiosa would be effective potential larvicides for mosquito control as well as antimicrobial agents with eco-friendly approach.

A new polyketide from the bark of Hypericum roeperianum Schimp. (Hypericaceae)

The isolation and spectroscopic data of a hitherto undescribed polyketide (1) from Hypericum roeperianum Schimp. (Hypericaceae) together with six known compounds (2-7) is herein reported. The structure elucidation is based on extensive 1D- and 2D-NMR, infrared, UV and MS experiments. The structures of the known compounds were confirmed by comparison of their spectroscopic data with those of similar reported compounds in the literature. Some of the isolated compounds had a significant activity against a panel of multidrug-resistant bacterial strains.Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2019.1677655.

A Pharmacological Overview of Alpinumisoflavone, a Natural Prenylated Isoflavonoid

Over the last decade, several studies demonstrated that prenylation of flavonoids enhances various biological activities as compared to the respective nonprenylated compounds. In line with this, the natural prenylated isoflavonoid alpinumisoflavone (AIF) has been explored for a number of biological and pharmacological effects (therapeutic potential). In this review, we summarize the current information on health-promoting properties of AIF. Reported data evidenced that AIF has a multitherapeutic potential with antiosteoporotic, antioxidant and anti-inflammatory, antimicrobial, anticancer, estrogenic and antiestrogenic, antidiabetic, and neuroprotective properties. However, research on these aspects of AIF is not sufficient and needs to be reevaluated using more appropriate methods and methodology. Further series of studies are needed to confirm these pharmacological effects, and this review should lay the basis for the design of respective investigations. Overall, despite the drawbacks of studies recorded, AIF exhibits a potential as drug candidate.

Molecular Informatics Studies of the Iron-Dependent Regulator (ideR) Reveal Potential Novel Anti-Mycobacterium ulcerans Natural Product-Derived Compounds

Buruli ulcer is a neglected tropical disease caused by the bacterium Mycobacterium ulcerans. Its virulence is attributed to the dermo-necrotic polyketide toxin mycolactone, whose synthesis is regressed when its iron acquisition system regulated by the iron-dependent regulator (ideR) is deactivated. Interfering with the activation mechanism of ideR to inhibit the toxin’s synthesis could serve as a possible cure for Buruli ulcer. The three-dimensional structure of the ideR for Mycobacterium ulcerans was generated using homology modeling. A library of 832 African natural products (AfroDB), as well as five known anti-mycobacterial compounds were docked against the metal binding site of the ideR. The area under the curve (AUC) values greater than 0.7 were obtained for the computed Receiver Operating Characteristics (ROC) curves, validating the docking protocol. The identified top hits were pharmacologically profiled using Absorption, Distribution, Metabolism, Elimination and Toxicity (ADMET) predictions and their binding mechanisms were characterized. Four compounds with ZINC IDs ZINC000018185774, ZINC000095485921, ZINC000014417338 and ZINC000005357841 emerged as leads with binding energies of −7.7 kcal/mol, −7.6 kcal/mol, −8.0 kcal/mol and −7.4 kcal/mol, respectively. Induced Fit Docking (IFD) was also performed to account for the protein’s flexibility upon ligand binding and to estimate the best plausible conformation of the complexes. Results obtained from the IFD were consistent with that of the molecular docking with the lead compounds forming interactions with known essential residues and some novel critical residues Thr14, Arg33 and Asp17. A hundred nanoseconds molecular dynamic simulations of the unbound ideR and its complexes with the respective lead compounds revealed changes in the ideR’s conformations induced by ZINC000018185774. Comparison of the lead compounds to reported potent inhibitors by docking them against the DNA-binding domain of the protein also showed the lead compounds to have very close binding affinities to those of the potent inhibitors. Interestingly, structurally similar compounds to ZINC000018185774 and ZINC000014417338, as well as analogues of ZINC000095485921, including quercetin are reported to possess anti-mycobacterial activity. Also, ZINC000005357841 was predicted to possess anti-inflammatory and anti-oxidative activities, which are relevant in Buruli ulcer and iron acquisition mechanisms, respectively. The leads are molecular templates which may serve as essential scaffolds for the design of future anti-mycobacterium ulcerans agents.

Simultaneously down-regulation of multiplex branch pathways using CRISPRi and fermentation optimization for enhancing β-amyrin production in Saccharomyces cerevisiae

The production of β-amyrin in Saccharomyces cerevisiae is still low due to the inability of effectively regulating the endogenous metabolic pathway for competitive synthesis of β-amyrin precursors. In this study, we focused on two branches of β-amyrin synthetics pathway that consume β-amyrin precursors (2,3-oxidosqualene and cytosolic acetyl-CoA) and regulated related genes (ADH1, ADH4, ADH5, ADH6, CIT2, MLS2 and ERG7). We developed a CRISPRi method by constructing a multi-gRNA plasmid to down-regulate the seven genes simultaneously, which is reported for the first time in S. cerevisiae. The average transcription inhibition efficiency of the seven genes reached as high as 75.5%. Furthermore, by optimizing the fermentation condition (including pH, inoculum size, initial glucose concentration and feed of glucose or ethanol) and increasing extracellular transportation via supplying methyl-β-cyclodextrin, β-amyrin concentration of engineered strain SGibSdCg increased by 44.3% compared with the parent strain SGib, achieving 156.7 mg/L which was the highest concentration of β-amyrin reported in yeast. The one-step down-regulation of multiple genes using CRISPRi showed high efficiency and promising future in improving the yields of natural products.

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One step down-regulation of seven genes using CRISPRi was successfully realized in Saccharomyces cerevisiae.

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Highest reported yield of β-amyrin had obtained, which is 44.2% higher than initial strain.

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Exportation of intracellular β-amyrin was boosted by adding methyl-β-cyclodextrin.

Investigation of the anti-TB potential of selected propolis constituents using a molecular docking approach

Human tuberculosis (TB), caused by Mycobacterium tuberculosis, is the leading bacterial killer disease worldwide and new anti-TB drugs are urgently needed. Natural remedies have long played an important role in medicine and continue to provide some inspiring templates for drug design. Propolis, a substance naturally-produced by bees upon collection of plant resins, is used in folk medicine for its beneficial anti-TB activity. In this study, we used a molecular docking approach to investigate the interactions between selected propolis constituents and four ‘druggable’ proteins involved in vital physiological functions in M. tuberculosis, namely MtPanK, MtDprE1, MtPknB and MtKasA. The docking score for ligands towards each protein was calculated to estimate the binding free energy, with the best docking score (lowest energy value) indicating the highest predicted ligand/protein affinity. Specific interactions were also explored to understand the nature of intermolecular bonds between the most active ligands and the protein binding site residues. The lignan (+)-sesamin displayed the best docking score towards MtDprE1 (−10.7 kcal/mol) while the prenylated flavonoid isonymphaeol D docked strongly with MtKasA (−9.7 kcal/mol). Both compounds showed docking scores superior to the control inhibitors and represent potentially interesting scaffolds for further in vitro biological evaluation and anti-TB drug design.

Iron and iron oxide nanoparticles are highly toxic to Culex quinquefasciatus with little non-target effects on larvivorous fishes

The control of filariasis vectors has been enhanced in several areas, but there are main challenges, including increasing resistance to insecticides and lack of cheap and eco-friendly products. The toxicity of iron (Fe⁰) and iron oxide (Fe₂O₃) nanoparticles has been scarcely investigated yet. We studied the larvicidal and pupicidal activity of Fe⁰ and Fe₂O₃ nanoparticles against Culex quinquefasciatus. Fe⁰ and Fe₂O₃ nanoparticles produced by green (using a Ficus natalensis aqueous extract) and chemical nanosynthesis, respectively, were analyzed by UV-Vis spectrophotometry, FT-IR spectroscopy, XRD analysis, SEM, and EDX assays. In larvicidal and pupicidal experiments on Cx. quinquefasciatus, LC₅₀ of Fe⁰ nanoparticles ranged from 20.9 (I instar larvae) to 43.7 ppm (pupae) and from 4.5 (I) to 22.1 ppm (pupae) for Fe₂O₃ nanoparticles synthesized chemically. Furthermore, the predation efficiency of the guppy fish, Poecilia reticulata, after a single treatment with sub-lethal doses of Fe⁰ and Fe₂O₃ nanoparticles was magnified. Overall, this work provides new insights about the toxicity of Fe⁰ and Fe₂O₃ nanoparticles against mosquito vectors; we suggested that green and chemical fabricated nano-iron may be considered to develop novel and effective pesticides.

Use of herbal extract from Artemisia herba-alba (Shih) in pharmaceutical preparations for dental hygiene

Antibiotic resistance in bacterial species is opening new avenues to search for alternative modes of antimicrobial treatment, medicinal plant extracts being one among them. The aim of this study was to access the possibility of medicinal plant extract from Shih in the manufacture of pharmaceutical preparations for oral hygiene specifically for the prevention and treatment of dental caries due to Streptococcus mutans. Antimicrobial effects of crude organic extract of Shih on S. mutans isolated from the saliva were examined by taking S. mutans with culture media only (−ve control); S. mutans treated with the antibiotic gentamicin (+ve control) and S. mutans treated with Shih. Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) were Determination by Iodonitrotetrazolium chloride (INT) colorimetric assay Time-kill dynamic assay was performed using broth microdilution method. The metabolic reason behind the bacteriostatic and bactericidal effect were studied by measuring the glucose utilization by the microbes, pH as a measure of acid production, nucleic acids quantitation to check the DNA status and inhibition of water-insoluble glucan synthesis were undertaken. Shih MIC for S. mutans was at 2.5 mg/ml and MBC was 4 mg/ml. S. mutans bacterial population started reclining within 60 min of incubation with Shih at MBC. Utilization of added glucose was very high at MIC due to bacteria overcoming the stress, whereas at MBC its utilization was less. Accordingly pH also became acidic to 2.9 with MIC and 4.03 with MBC. There was a great degree of inhibition in the formation of nucleic acids indicating this crude extract interferes with DNA replication. Inhibition of glucan synthesis was to the tune of 45% as compared to control. Thus we conclude that Shih has potentially effective antibacterial activity hence it can be proposed as a potentially effective antiplaque and anticariogenic agent in the form of mouth wash or gum paint. However, the cytotoxicity of the extract needs to be evaluated in in-vitro and in-vivo conditions before it is considered as a safe antiplaque and anticariogenic agent.

Characterization of Anti-bacterial Compounds from the Seed Coat of Chinese Windmill Palm Tree (Trachycarpus fortunei)

The increasing of multidrug resistance in bacterial associated infections has impaired the current antimicrobial therapy and it forces the search for other alternatives. In this study, we aimed to find the in vitro antibacterial activity of seed coat of Trachycarpus fortunei against a panel of clinically important bacterial species. Ethanolic extracts of target tissues were fractionated through macro porous resin by column chromatography, using ethanol as an organic solvent with a concentration gradient of 0-100%, each along with 20% concentration increment. The minimum inhibitory (MIC) concentrations of all fractions were measured. It is found that 20% ethanolic fraction showed the most significant inhibition against tested bacterial species. All fractions were analyzed by Ultra-Performance Liquid Chromatography/mass spectrometry (UPLC/MS) and compounds were identified by comparing mass spectra with standard libraries. By pairing the identified compounds from different fractions with the antibacterial activity of each fraction, it was shown that compounds stearamide (7), 1-(4-Fluorophenyl)-2-(methylthio)-1H-imidazole-5-carboxylic acid (9) and 2,4,5 triacetoxybiphenyl (10) topped in the list for anti-bacterial activity. Further experiment with pure chemicals verified that compounds 9 and 10 have antibacterial activity against Gram-negative bacteria. Whereas, the lowest MIC value (39.06 μg/mL) was obtained by compound 10 against Staphylococcus epidermidis. Hence, the seed coat of T. fortunei with its antimicrobial spectrum could be a good candidate for further bactericidal research.

Chemotaxonomic Diversity of Three Ficus Species: Their Discrimination Using Chemometric Analysis and Their Role in Combating Oxidative Stress

BACKGROUND

Genus Ficus (Moraceae) constitutes more than 850 species and about 2000 varieties and it acts as a golden mine that could afford effective and safe remedies combating many health disorders.

OBJECTIVES

Discrimination of Ficus cordata, Ficus ingens, and Ficus palmata using chemometric analysis and assessment of their role in combating oxidative stress.

MATERIALS AND METHODS

Phytochemical profiling of the methanol extracts of the three Ficus species and their successive fractions was performed using high-performance liquid chromatography/electrospray ionization mass spectrometry. Their discrimination was carried out using the obtained spectral data applying chemometric unsupervised pattern-recognition techniques, namely, principal component analysis and hierarchical cluster analysis. In vitro hepatoprotective and antioxidant evaluation of the samples was performed using human hepatocellular carcinoma cells challenged by carbon tetrachloride (CCl4).

RESULTS

Altogether, 22 compounds belonging to polyphenolics, flavonoids, and furanocoumarins were identified in the three Ficus species. Aviprin is the most abundant compound in F. cordata while chlorogenic acid and psoralen were present in high percentages in F. ingens and F. palmata, respectively. Chemometric analyses showed that F. palmata and F. cordata are more closely related chemically to each other rather than F. ingens. The ethyl acetate fractions of all the examined species showed a marked hepatoprotective efficacy accounting for 54.78%, 55.46%, and 56.42% reduction in serum level of alanine transaminase and 56.82%, 54.16%, and 57.06% suppression in serum level of aspartate transaminase, respectively, at 100 μg/mL comparable to CCl4-treated cells.

CONCLUSION

Ficus species exhibited a no table antioxidant and hepatoprotective activity owing to their richness in polyphenolics and furanocoumarins.

SUMMARY

Ficus cordata, Ficus ingens, and Ficus palmata were analyzed using high-performance liquid chromatography/electrospray ionization mass spectrometry that revealed their richness with polyphenolics and furanocoumarinsDiscrimination of the three species was performed using spectral data coupled with chemometrics that showed that F. palmata and F. cordata are chemically related to each other rather than F. ingensIn vitro hepatoprotective and antioxidant evaluation was performed using human hepatocellular carcinoma cells. The ethyl acetate fractions of all the examined species showed a marked hepatoprotective efficacyFicus species exhibited notable activities due to polyphenolics and furanocoumarins. Abbreviations used: ALT: Alanine transaminase, AST: Aspartate transaminase, CCl4: Carbon tetrachloride, DMEM: Dulbecco's Modified Eagle's medium, DMSO: Dimethyl sulfoxide, EDTA: Ethylenediaminetetraacetic acid, FBS: Fetal bovine serum, FCA: Ficus cordata remaining aqueous fraction, FCB: Ficus cordata n-butanol fraction, FCE: Ficus cordata ethyl acetate fraction, FCP: Ficus cordata petroleum ether fraction, FCT: Ficus cordata total methanol extract, FIA: Ficus ingens remaining aqueous fraction, FIB: Ficus ingens n-butanol fraction, FIE: Ficus ingens ethyl acetate fraction, FIP: Ficus ingens petroleum ether fraction, FIT: Ficus ingens total methanol extract, FPA: Ficus palmata remaining aqueous fraction, FPB: Ficus palmata n-butanol fraction, FPE: Ficus palmata ethyl acetate fraction, FPP: Ficus palmata petroleum ether fraction, FPT: Ficus palmata total methanol extract, GSH: Reduced glutathione, HepG2 cells: Human hepatocellular carcinoma, HPLC-ESI-MS: High-performance liquid chromatography/electrospray ionization mass spectrometry, and SOD: Superoxide dismutase.

Potential of Central, Eastern and Western Africa Medicinal Plants for Cancer Therapy: Spotlight on Resistant Cells and Molecular Targets

Cancer remains a major health hurdle worldwide and has moved from the third leading cause of death in the year 1990 to second place after cardiovascular disease since 2013. Chemotherapy is one of the most widely used treatment modes; however, its efficiency is limited due to the resistance of cancer cells to cytotoxic agents. The present overview deals with the potential of the flora of Central, Eastern and Western African (CEWA) regions as resource for anticancer drug discovery. It also reviews the molecular targets of phytochemicals of these plants such as ABC transporters, namely P-glycoprotein (P-gp), multi drug-resistance-related proteins (MRPs), breast cancer resistance protein (BCRP, ABCG2) as well as the epidermal growth factor receptor (EGFR/ErbB-1/HER1), human tumor suppressor protein p53, caspases, mitochondria, angiogenesis, and components of MAP kinase signaling pathways. Plants with the ability to preferentially kills resistant cancer cells were also reported. Data compiled in the present document were retrieved from scientific websites such as PubMed, Scopus, Sciencedirect, Web-of-Science, and Scholar Google. In summary, plant extracts from CEWA and isolated compounds thereof exert cytotoxic effects by several modes of action including caspases activation, alteration of mitochondrial membrane potential (MMP), induction of reactive oxygen species (ROS) in cancer cells and inhibition of angiogenesis. Ten strongest cytotoxic plants from CEWA recorded following in vitro screening assays are: Beilschmiedia acuta Kosterm, Echinops giganteus var. lelyi (C. D. Adams) A. Rich., Erythrina sigmoidea Hua (Fabaceae), Imperata cylindrical Beauv. var. koenigii Durand et Schinz, Nauclea pobeguinii (Pobég. ex Pellegr.) Merr. ex E.M.A., Piper capense L.f., Polyscias fulva (Hiern) Harms., Uapaca togoensis Pax., Vepris soyauxii Engl. and Xylopia aethiopica (Dunal) A. Rich. Prominent antiproliferative compounds include: isoquinoline alkaloid isotetrandrine (51), two benzophenones: guttiferone E (26) and isoxanthochymol (30), the isoflavonoid 6α-hydroxyphaseollidin (9), the naphthyl butenone guieranone A (25), two naphthoquinones: 2-acetylfuro-1,4-naphthoquinone (4) and plumbagin (37) and xanthone V1 (46). However, only few research activities in the African continent focus on cytotoxic drug discovery from botanicals. The present review is expected to stimulate further scientific efforts to better valorize the African flora.

Antibacterial and antibiotic resistance modulatory activities of leaves and bark extracts of Recinodindron heudelotii (Euphorbiaceae) against multidrug-resistant Gram-negative bacteria

Background

Recinodindron heudelotii (Euphorbiaceae) is a plant used in Africa, particularly in Cameroon to treat various ailments including bacterial infections. In this study, we evaluated the extracts of the leaves (RHL) and bark (RHB) of R. heudelotii for their antibacterial and antibiotic resistance modulating activities against 29 Gram-negative bacteria, including multidrug-resistant (MDR) phenotypes.

Methods

The broth micro-dilution assay was used to evaluate the antibacterial activity, and the antibiotic resistance modulating effects of the plant extracts.

Results

RHL displayed the most important spectrum of activity with minimal inhibitory concentrations (MICs) values ranging from 256 to 1024 μg/mL against 75.86% of the 29 tested bacteria strains while RHB was not active. RHL also showed killing effects with minimal bactericidal concentrations (MBCs) ranging from 256 to 1024 μg/mL. The activities of tetracycline and kanamycin associated with RHL were improved on 88.89% and 77.78% of the tested MDR bacteria, at MIC/2 at MIC/4 respectively, with 2 to 16-folds decreasing of MIC. This suggests the antibiotic resistance modulating effects of these antibiotics.

Conclusion

The present study provides data indicating a possible use of the leaves extract of Recinodindron heudelotii alone or in association with common antibiotics in the fight against bacterial infections including those involving MDR bacteria.

IN VITRO EFFICACY OF EXTRACTS FROM PLANTS USED BY SMALL-HOLDER FARMERS IN THE TREATMENT OF DERMATOPHILOSIS IN CATTLE

Background:

Bovine dermatophilosis, an important skin disease of cattle caused by Dermatophilus congolensis, negatively impacts the livelihoods of small-holder farmers in Zimbabwe. This impact is through, morbidity, loss of draught animal power, costs incurred to manage the disease, losses associated with devalued damaged hides and the resultant culling of some of the affected cattle. Due to the inaccessibility of conventional drugs to manage bovine dermatophilosis, farmers have been reported to use local medicinal plants to manage the disease. The aim of the study was to evaluate the in vitro antimicrobial activities of three plants that small-holder farmers in Zimbabwe used to manage bovine dermatophilosis.

Methods:

Dried plant materials were ground into powder and extracted individually using, water, 80 % acetone and 80 % methanol. The antimicrobial properties of the plants were evaluated against two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and one Gram-positive (Staphylococcus aureus) reference bacterial strains. They were further evaluated against a field isolate of Dermatophilus congolensis. The assays used were the disc diffusion, minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC).

Results:

Acetone and methanol extracts had superior inhibitory activities than did those of water. Pterocarpus angolensis DC extracts had better inhibitory properties with absolute MIC values of 0.156 – 5 mg/ml, Cissus Quadrangularis L had MIC values in the range 0.156 – 5 mg/ml while that of Catunaregam spinosa Thunb, Terveng was 0.156 – 10 mg/ml. Dermatophilus congolensis was more sensitive to Pterocarpus angolensis DC average MIC = 0.63 mg/ml than to Cissus quadrangularis L average MIC = 1.25 mg/ml and Catunaregam. spinosa Thunb, Terveng average MIC = 2.08 mg/ml.

Conclusion:

These results suggest the potential antibacterial activities of extracts of the three plants and hence farmers are, in a way, justified in using the plants. Better results (lower MIC) could be obtained by extracting and evaluating pure active compounds of the plants.

Antibacterial activity of six medicinal Cameroonian plants against Gram-positive and Gram-negative multidrug resistant phenotypes

Background

Infectious diseases due to multidrug-resistant bacteria are one of the causes of treatment failures contributing to an increase in mortality and/or morbidity. In this study, we evaluated the antibacterial potential of different parts of six medicinal plants namely Alstonia boonei, Ageratum conyzoides, Croton macrostachys, Cassia obtusifolia, Catharanthus roseus and Paullinia pinnata against a panel of 36 multi-drug resistant (MDR) Gram-negative and Gram-positive bacteria.

Methods

Minimum Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) of the methanol extracts from different parts of the plants were determined using broth microdilution method; standard phytochemical methods were used for phytochemical screening.

Results

Several phytochemical classes such as polyphenols, sterols, triterpenes, alkaloids, flavonoids and saponins were identified in the plant extracts. MIC values obtained ranged from 64 to 1024 μg/mL. Leaves extract of Catharanthus roseus (86.11 %), Croton macrostachys (83.33 %) and Paullinia pinnata (80.55 %) displayed the best antibacterial spectra. The lowest MIC value of 64 μg/mL was obtained with the Paullinia pinnata stems extract and Cassia obtusifolia extract against the strain of Staphylococcus aureus MRSA8. Results also showed that the tested samples generally displayed bacteriostatic effects with MBC values obtained in only 3.35 % of the cases where plant extracts were active.

Conclusion

The results obtained at the end of this study demonstrate for the first time the antibacterial activity of the studied medicinal plants against MDR bacteria. The tested plants could be a reservoir of molecules to fight against MDR bacterial infections.

Antibacterial activities of the methanol extracts of Canarium schweinfurthii and four other Cameroonian dietary plants against multi-drug resistant Gram-negative bacteria

Bacterial infections are among the major cause of morbidity and mortality worldwide. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of five Cameroonian edible plants namely Colocasia esculenta, Triumfetta pentandra, Hibiscus esculentus, Canarium schweinfurthii and Annona muricata against a panel of 19 multidrug resistant Gram-negative bacterial strains. The liquid broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The preliminary phytochemical screening of the extracts was conducted according to the standard phytochemical methods. Results showed that all extracts contained compounds belonging to the classes of polyphenols, triterpenes and steroids, other classes of chemicals being selectively distributed. Canarium schweinfurthii extract showed the best activity with MIC values ranging from 64 to 1024 μg/mL against 89.5% of the 19 tested bacteria strains. MIC values below or equal to 1024 μg/mL were also recorded with Triumfetta pentandra, Annona muricata, Colocasia esculenta and Hibiscus esculentus extracts respectively against 15/19 (78.9%), 11/19 (57.9%), 10/19 (52.6%) and 10/19 (52.6%) tested bacteria. Extract from C. schweinfurthii displayed the lowest MIC value (64 μg/mL) against Escherichia coli AG100ATet. Finally, the results of this work provide baseline information for the use of C. esculenta, T. pentandra, H. esculentus, C. schweinfurthii and A. muricata in the treatment of bacterial infections including multidrug resistant phenotypes.

Cytotoxicity of seven naturally occurring phenolic compounds towards multi-factorial drug-resistant cancer cells

INTRODUCTION

In medical oncology, multi-drug resistance (MDR) of cancer cells continues to be a major impediment. We are in quest of novel anti-proliferative agents to overcome drug-resistant tumor cells.

METHODS

In the present study, we investigated the cytotoxicity of 7 naturally occurring phenolic compounds including two isoflavonoids alpinumisoflavone (1) and laburnetin (2), one biflavonoid amentoflavone (3), three lignans pycnanthulignene A (4), pycnanthulignene B (5), and syringaresinol (7) and one xanthone, euxanthone (6) against 9 drug-sensitive and MDR cancer cell lines. The resazurin reduction assay was used to evaluate the cytotoxicity of these compounds, whilst caspase-Glo assay was used to detect caspase activation. Cell cycle, mitochondrial membrane potential (MMP) and levels of reactive oxygen species (ROS) were all analyzed via flow cytometry.

RESULTS

The IC50 values for the investigational phenolics ranged from 5.91 µM (towards leukemia CEM/ADR5000 cells) to 65.65 µM (towards drug-resistant breast adenocarcinoma MDA-MB-231-BCRP cells) for 1, 27.63 µM (towards leukemia CCRF-CEM cells) to 107.57 µM (towards MDA-MB-231-pcDNA cells) for 2, from 5.84 µM (towards CEM/ADR5000 cells) to 65.32 µM (towards colon carcinoma HCT116 (p53(-/-)) cells) for 4 and 0.20 µM (towards CCRF-CEM cells) to 195.12 µM (towards leukemia CEM/ADR5000) for doxorubicin. Phenolics 3, 5, 6 and 7 displayed selectivity cytotoxic effects on cancer cells lines. Compounds 1 and 4 induced apoptosis in CCRF-CEM cells, mediated by loss of MMP and increase ROS production.

CONCLUSIONS

The studied phenolics and mostly isoflavonoid 1 and lignan 4 are potential cytotoxic natural products that deserve more investigations to develop novel antineoplastic drugs against multifactorial drug-resistant cancers.

Antimicrobial and antioxidant activity and chemical characterisation of Erythrina stricta Roxb. (Fabaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The bark of Erythrina stricta Roxb. (Fabaceae) has been used in Indian indigenous systems as a remedy for rheumatism, stomach-ache, asthma, dysentery, contact dermatitis, eczema and skin infections. However, there have been limited phytochemical or biological studies on the bark of E. stricta and there are no studies that align with its traditional medicinal uses.

AIM OF THE STUDY

The aim of this study was to assess the antimicrobial and antioxidant activity of the stem bark of E. stricta to support its topical use in the treatment of contact dermatitis, eczema and skin infections and to isolate and identify any bioactive compounds.

MATERIALS AND METHODS

MTT microdilution and disc diffusion assays were used to determine the antimicrobial activities of n-hexane, dichloromethane, ethyl acetate, methanol and water extracts of the bark of E. stricta. Column and preparative thin layer chromatography were used for the purification of the dichloromethane extract. The structures of the compounds isolated were elucidated by extensive 1D and 2D NMR spectroscopic techniques and comparison with published data. The antioxidant activities of the extracts were determined by DPPH free radical scavenging and FRAP assays and the antioxidant activity of the pure compounds by dot-blot and DPPH staining methods.

RESULTS

The dichloromethane, ethyl acetate, and n-hexane extracts showed the most significant activity with MIC values of 7.8µg/mL, 125µg/mL, and 125µg/mL against a sensitive strain of Staphylococcus aureus. The dichloromethane and ethyl acetate extracts also showed significant activity against Candida albicans with MIC values of 125µg/mL and 1mg/mL respectively. GC-MS analysis of the n-hexane extract showed the presence of the antibacterial and antifungal compounds β-caryophyllene, caryophyllene oxide, α-selinene, β-selinene, selin-11-en-4-α-ol, α-copaene and δ-cadenine. Phytochemical studies of the dichloromethane extract led to the isolation of the novel compound erynone (1), together with six known compounds; wighteone (2), alpinum isoflavone (3), luteone (4), obovatin (5), erythrinassinate B (6) and isovanillin (7). Luteone (4) exhibited the most significant antibacterial activity with minimum inhibitory quantity (MIQ) values of 1.88µg, 1.88µg and 3.75µg, respectively, against sensitive (MSSA) and resistant strains (MRSA and MDRSA) of S. aureus using a TLC bioautography assay. Erynone (1) exhibited the greatest DPPH free radical scavenging activity.

CONCLUSIONS

Seven compounds, including a new chromanone, were isolated from the antimicrobial dichloromethane extract of the stem bark of E. stricta. Six of the seven compounds showed antibacterial and/or antioxidant activities. These findings provide support for the customary (traditional and contemporary) use of E. stricta bark for the treatment of skin and wound infections.

Antibacterial activities of the methanol extracts of Albizia adianthifolia, Alchornea laxiflora, Laportea ovalifolia and three other Cameroonian plants against multi-drug resistant Gram-negative bacteria

In the last 10 years, resistance in Gram-negative bacteria has been increasing. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of six Cameroonian medicinal plants Albizia adianthifolia, Alchornea laxiflora, Boerhavia diffusa, Combretum hispidum, Laportea ovalifolia and Scoparia dulcis against a panel of 15 multidrug resistant Gram-negative bacterial strains. The broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The preliminary phytochemical screening of the extracts was conducted according to the reference qualitative phytochemical methods. Results showed that all extracts contained compounds belonging to the classes of polyphenols and triterpenes, other classes of chemicals being selectively distributed. The best antibacterial activities were recorded with bark and root extracts of A. adianthifolia as well as with L. ovalifolia extract, with MIC values ranging from 64 to 1024 μg/mL on 93.3% of the fifteen tested bacteria. The lowest MIC value of 64 μg/mL was recorded with A. laxiflora bark extract against Enterobacter aerogenes EA289.

Finally, the results of this study provide evidence of the antibacterial activity of the tested plants and suggest their possible use in the control of multidrug resistant phenotypes.

In vitro antibacterial activities of p-toluenesulfonyl-hydrazinothiazoles and hydrazinoselenazoles against multi-drug resistant Gram-negative phenotypes

BACKGROUND

Bacterial multidrug resistance (MDR) constitutes a major hurdle in the treatment of infectious diseases worldwide. The present study was designed to evaluate the antibacterial activities of synthetic p-toluenesulfonyl-hydrazinothiazoles against multidrug resistant Gram-negative bacteria.

METHODS

The broth microdilution method was used to determine the minimal inhibitory concentrations (MIC).

RESULTS

The results demonstrated that the best activities were obtained with hydrazinoselenazoles. p-Chloro-benzyliden-selenosemicarbazide, 4-methyl-2-[(4-chloro-benzyliden)-hydrazinyl]-1,3-selenazole, p-chloro-benzoyl-selenosemicarbazide and 4-chloromethyl-2-[(4-chlorobenziliden)-N-acetyl-hydrazinyl]-1,3-selenazole were more active than the choramphenicol on Klebsiella pneumoniae KP63. Tested alone, the lowest MIC value of 16 mg/L was obtained with p-methoxy-benzyliden-selenosemicarbazide against Enterobacter aerogenes ATCC13048, K. pneumoniae ATCC112296 and KP55. Tested in the presence of an efflux pump inhibitor, phenylalanine arginine β-naphthylamide (PAβN), the activity of p-chloro-benzyliden-selenosemicarbazide, 4-methyl-2-[(4-chloro-benzyliden)-hydrazinyl]-1,3-selenazole, p-chloro-benzoyl-selenosemicarbazide and p-methoxy-benzyliden-selenosemicarbazide significantly increased with MIC values below 10 mg/L obtained respectively on 43.8 %, 31.3 %, 62.5 % and 100 % of the 16 tested bacterial strains. The lowest MIC value of 0.5 mg/L in the presence of PAβN was recorded with p-chloro-benzoyl-selenosemicarbazide against Escherichia coli ATCC8739 and KP55 as well as p-methoxy-benzyliden-selenosemicarbazide against E. aerogenes KP55. p-Chloro-benzyliden-selenosemicarbazide and p-chloro-benzoyl-selenosemicarbazide contained the same pharmacophore as p-methoxy-benzyliden-selenosemicarbazide.

CONCLUSION

This study indicates that p-chloro-benzyliden-selenosemicarbazide, p-chloro-benzoyl-selenosemicarbazide and p-methoxy-benzyliden-selenosemicarbazide could be explored more to develop novel antimicrobial drugs to fight MDR bacterial infections.

Antibacterial and antibiotic-modifying activities of three food plants (Xanthosoma mafaffa Lam., Moringa oleifera (L.) Schott and Passiflora edulis Sims) against multidrug-resistant (MDR) Gram-negative bacteria

Background

The present study was designed to investigate the antibacterial activities of the methanol extract of three edible plants, namely Xanthosoma mafaffa, Moringa oleifera and Passiflora edulis and their synergistic effects with some commonly used antibiotics against MDR Gram-negative bacteria expressing active efflux pumps.

Methods

Broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of the extracts, as well as those of antibiotics in association with the extracts.

Results

The phytochemical test indicate that all tested crude extracts contained polyphenols, triterpenes and steroids whilst other phytochemical classes were selectively distributed. Extracts showed antibacterial activities with minimum inhibitory concentrations ranging from 128-1024 μg/mL on the majority of the 19 tested Gram-negative bacterial strains. Extract from the pericarp of P. edulis inhibited the growth of 89.5 % of the 19 tested bacterial strains, the lowest minimal inhibitory concentration (MIC) value of 128 μg/mL being recorded against Escherichia coli AG100 strain. In the presence of Phenylalanine-Arginine β-Naphtylamide (PAβN)], an efflux pump inhibitor (EPI), the activity of the extract from X. mafaffa increased on 40 % of tested strains. In combination with antibiotics, extracts of X. mafaffa, M. oleifera and pericarp of P. edulis showed synergistic effects with some antibiotics against more than 75 % of the tested bacteria.

Conclusion

The results of the present study indicate that the tested plants may be used in the treatment of bacterial infections including the multi-resistant bacteria.

Ngadjui B, Kuete V. Antibacterial activities of the methanol extracts and compounds from Erythrina sigmoidea against Gram-negative multi-drug resistant phenotypes

Background

In the present study, the methanol extracts from the leaves, as well as compounds namely sigmoidin I (1), atalantoflavone (2), bidwillon A (3), neocyclomorusin (4), 6α-hydroxyphaseollidin (5) and neobavaisoflavone (6) (from the bark extract) were tested for their activities against a panel of Gram-negative bacteria including multi-drug resistant (MDR) phenotypes.

Methods

Broth microdilution method was used to determine the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of the extracts as well as compounds 1–6.

Results

The MIC results indicated that the crude extracts from the leaves and bark of this plant were able to inhibit the growth of 96.3 % of the 27 tested bacteria. Compounds 2–6 displayed selective activities, their inhibitory effects being obtained on 8.3 %, 41.7 %, 58.3 %, 58.3 % and 66.7 % of tested bacteria respectively for 2, 3, 5, 6 and 4. The lowest MIC value of 8 μg/mL was obtained with 6 against Escherichia coli ATCC8739, Enterobacter cloacae ECCI69, Klebsiella pneumoniae KP55, Providencia stuartii NAE16 and Pseudomonas aeruginosa PA01.

Conclusion

The present study demonstrates that Erythrina sigmoidea is a potential source of antibacterial drugs to fight against MDR bacteria. Neobavaisoflavone (6) is the main antibacterial consituents of the bark crude extract.

Antibacterial activity of nineteen selected natural products against multi-drug resistant Gram-negative phenotypes

The present study was designed to assess the antimicrobial activity of 19 natural products belonging to terpenoids, alkaloids, thiophenes and phenolics against a panel of 14 Gram-negative multidrug-resistant (MDR) bacteria. The results demonstrated that amongst the studied compounds, alkaloids and terpenoids were less active contrary to flavonoids: neocyclomorusin (3) and candidone (6) and isoflavonoids: neobavaisoflavone (8) and daidzein (12). Thiophene, 2-(penta-1,3-diynyl)-5-(3,4-dihydroxybut-1-ynyl)thiophene (17) showed moderate and selective activities. Compounds 3, 6, 8 and 12 displayed minimal inhibitory concentration (MIC) ranged from 4 to 256 μg/mL on all the 14 tested bacteria. MIC values below 10 μg/mL were obtained with 8, 3, 6 and 12 against 50, 42.9, 35.7 and 21.4 % of the tested bacteria. The lowest MIC value of 4 μg/mL was obtained with compound 3 against Klebsiella pneumoniae ATCC11296, Enterobacter cloacae BM47, compound 6 against Escherichia coli ATCC8739, K. pneumoniae ATCC11296, E. cloacae BM47 and compound 8 against K. pneumoniae ATCC11296 and E. cloacae BM47. The activity of flavonoid 3 was better or equal to that of chloramphenicol in all tested K. pneumoniae,Providencia stuartii, E. aerogenes, E. cloacae and Pseudomonas aeruginosa strains. Within isoflavonoids, neobavaisoflavone scaffold was detected as a pharmacophoric moiety. This study indicates that natural products such as 3, 6 and 8 could be explored more to develop antimicrobial drugs to fight MDR bacterial infections.

Anti-Staphylococcus aureus activity of methanol extracts of 12 plants used in Cameroonian folk medicine

BACKGROUND

The emergence of bacterial infections including those associated with Staphylococcus aureus causes a benefit of interest to medicinal plants as an effective means of control. The present study was designed to investigate the activities of 12 selected Cameroonian medicinal plants against S. aureus isolates.

METHODS

The plant extracts were prepared by maceration in methanol at laboratory temperature. Qualitative phytochemical analysis was performed by chemical reaction methods. The broth microdilution method was used to evaluate the activities of plant extracts against 11 S. aureus clinical isolates.

RESULTS

Dacryodes edulis was found to have significant antibacterial activity on all the S. aureus isolates (MIC = 64-256 µg/ml). Occimum gratissimum revealed significant inhibitory activity on 9 of the 11 isolates while Commelina erecta and Spilanthes filicaulis revealed similar results on 6 of the 11 clinical isolates.

CONCLUSION

The present findings showed that D. eduli, O. gratissimum, C. erecta and S. filicaulis possess interesting inhibitory properties against S. aureus species. These plants could therefore be good candidates to overcome infectious diseases associated with these microorganisms.

Penicillium chrysogenum DSOA associated with marine sponge (Tedania anhelans) exhibit antimycobacterial activity

A strain of Penicillium chrysogenum was isolated from Tedania anhelans (marine sponge) collected from Indian Ocean (8°22'30″N latitude and 76°59'16″ longitude) and deposited in culture collection centers. The strain subjected to different culture conditions for production of extrolites were extracted using ethyl acetate and chloroform. When both extracts were subjected for antibacterial activity, latter had high activity. Minimum inhibitory concentration of chloroform extract ranged from 31.25-1000 μg/mL in tested microbes such as, Mycobacterium tuberculosis H37Ra, Mycobacterium avium, Mycobacterium fortuitum, Mycobacterium smegmatis, Mycobacterium vaccae, Staphylococcus aureus, Aeromonas hydrophila, Pseudomonas aeruginosa and Vibrio cholerae. No cytotoxicity was observed in Vero cell line up to 399.10 μg/mL. Antibacterial activity previously reported by Parameswaran et al. in 1997 from ethyl acetate extract of T. anhelans might be due to the diketopiperazines, Cyclo-(L-Pro-L-Phe) and Cyclo-(L-Leu-L-Pro) produced by the associated fungi-P. chrysogenum DSOA. It is producing a metabolites having antimycobacterial activity, a first report.