Antibacterial activity of some African medicinal plants used traditionally against infectious diseases

Characterization and comparative evaluation of wound healing potential of Ajugarin I and Ajuga bracteosa Wall. ex Benth

Ajuga bracteosa (family: Lamiaceae), commonly known as kauri booti, is an important ethnomedicinal plant. The current research was conducted to appraise and compare the in vitro antioxidant and antibacterial profiles as well as in vivo wound healing potentials of Ajugarin I and A. bracteosa extract. Ajugarin I and polyphenols in A. bracteosa were enumerated by reversed-phase high-performance liquid chromatography analysis that confirmed significant amounts of Ajugarin I (2.2 ± 0.02 μg/mg DW) and other phenolic compounds (14 out of 17 standards). A. bracteosa (374.4 ± 0.20 µg AAE/mg of DW, 201.9 ± 0.20 µg AAE/mg of DW, 87 ± 0.30%) showed a higher antioxidant profile compared to Ajugarin I (221.8 ± 0.50 µg AAE/mg of DW, 51.8 ± 0.40 µg AAE/mg of DW, 27.65 ± 0.80%) with 1.86-, 3.89-, and 3.15-fold greater activity in ferric reducing antioxidant power, total antioxidant capacity, and free radical scavenging assays, respectively. Likewise, A. bracteosa showed antibacterial activity against 3/5 strains (MIC 25-200 μg/ml) than Ajugarin I (2/5 strains; MIC 50-200 μg/ml). Hemolytic (<2% hemolysis) and dermal toxicity tests rendered both samples non-toxic. Additionally, A. bracteosa (100 ± 2.34% at day 12; 9.33 ± 0.47 days) demonstrated 1.11- and 1.24-fold higher percent wound contraction and epithelization time, respectively, than Ajugarin I (95.6 ± 1.52% at day 12; 11.6 ± 0.47 days) as assessed by an excision wound model in mice. Histopathological examination further reinforced the better wound healing potential of A. bracteosa with good epithelization, collagen synthesis, fibroblast proliferation, and revascularization. Briefly, we endorse the significant comparative antioxidant, antibacterial, and wound healing activities of A. bracteosa and Ajugarin I and present these as prospective candidates for wound healing drugs.

Daniellia oliveri (Rolfe) Hutch and Dalziel: Antimicrobial Activities, Cytotoxicity Evaluation, and Phytochemical Identification by GC-MS

During a previous study that identified plants used in traditional medicine in Togo to treat infectious diseases, Daniellia oliveri was specifically reported to treat intertrigo and candidiasis. Consequently, to explore the anti-infective potential of this plant, we investigated the antibacterial and the antifungal activity of the plant's parts, as well as the cytotoxic activities of raw extracts and subsequent fractions, and the chemical composition of the most active fractions. In order to evaluate the antimicrobial activity, MICs were determined using the broth dilution method. Then, the most active fractions were evaluated for cytotoxicity by using normal human cells (MRC-5 cells) via the MTT assay. Finally, the most active and not toxic fractions were phytochemically investigated by GC-MS. Interestingly, all the raw extracts and fractions were active against the bacteria tested, with MICs ranging from 16 µg/mL to 256 µg/mL, while no antifungal activity was observed at 256 µg/mL, the highest tested concentration. Moreover, no toxicity was observed with most of the active fractions. The subsequent chemical investigation of the most interesting fractions led to identifying terpenes, phytosterols, phenolic compounds, and fatty acids as the main compounds. In conclusion, this study demonstrated that D. oliveri possesses valuable antibacterial activities in accordance with traditional use.

An Annotated Inventory of Tanzanian Medicinal Plants Traditionally Used for the Treatment of Respiratory Bacterial Infections

This review comprehensively covers and analyzes scientific information on plants used in Tanzanian traditional medicine against respiratory diseases. It covers ethnobotanical and ethnopharmacological information extracted from SciFinder, Google Scholar, and Reaxys as well as the literature collected at the Institute of Traditional Medicine in Dar-es-Salaam. Crude extracts and fractions of 133 plant species have literature reports on antimicrobial bioassays. Of these, 16 plant species had a minimum inhibitory activity of MIC ≤ 50 µg/mL. Structurally diverse compounds were reported for 49 plant species, of which 7 had constituents with MIC ≤ 5 µg/mL against various bacteria: Bryophyllum pinnatum (Lam.) Oken, Warburgia ugandensis Sprague, Diospyros mespiliformis Hochst. ex DC., Cassia abbreviata Oliv., Entada abyssinica A. Rich., Strychnos spinosa Lam., and Milicia excelsa (Welw.) C.C. Berg. The low number of antimicrobial active extracts and compounds suggests that antibacterial and antimycobacterial drug discovery needs to have a fresh look at ethnobotanical information, diverting from too reductionist an approach and better taking into account that the descriptions of symptoms and concepts of underlying diseases are different in traditional African and modern Western medicine. Nevertheless, some structurally diverse compounds found in anti-infective plants are highlighted in this review as worthy of detailed study and chemical modification.

Momordica balsamina: phytochemistry and pharmacological potential of a gifted species

Momordica balsamina L. (Cucurbitaceae), frequently named balsam apple, southern balsam pear or African pumpkin, is a vegetable with high nutritional value, being mostly used as food in sub-Saharan Africa. It has also been largely used in traditional medicine to treat several diseases, such as malaria fevers and diabetes. As a member of the Cucurbitaceae family, the main constituents are cucurbitane-type triterpenoids, with different oxidation patterns, named cucurbitacins. This review aims at summarizing our contribution to the phytochemical study of M. balsamina and the evaluation of the isolated cucurbitacins and derivatives as multidrug resistance reversers in cancer cells and bacteria. In this way, the selective antiproliferative activity against multidrug resistant cancer cells of cucurbitacins obtained from M. balsamina, their ability as P-glycoprotein inhibitors in cancer cells overexpressing this ABC transporter, as well as efflux pump inhibitors in resistant bacteria strains are reviewed. Moreover, the in vitro antimalarial activity of cucurbitacins and acyl derivatives against the blood and liver-stages of Plasmodium strains, and the in vivo activity of selected compounds is also reviewed. Besides our work, edible and medicinal uses, and other studies mainly reporting the biological activities of M. balsamina extracts, such as antidiabetic, antibacterial, anti-inflammatory, and antioxidant properties are also addressed.

Phytochemical and biological attributes of Bauhinia variegata L. (Caesalpiniaceae)

Abstract Bauhinia variegata plant is a very popular and traditionally potent ethnomedicine. Therefore, it is need of hour to study ameliorative characteristics of B. variegata for novel secondary metabolites. The current study was designed to explore antiproliferative potential of B. variegata due to scant reports on this aspect. Extracts of various parts (flowers, leaves, bark, stem, and roots) were prepared by successive maceration using organic solvents in increasing order of polarity (n-hexane, ethyl acetate, methanol, and water). The determination of polyphenolic contents was done by using colorimetric methods while antioxidant potential was measured using reducing power assay. Brine shrimp lethality assay was performed for determining preliminary cytotoxicity and antiproliferative activity against breast cancer MCF-7 cell line using MTT protocols. Moreover, antimicrobial activities were detected by using disc diffusion assay. The alpha-amylase assay was performed to monitor the antidiabetic potential of the plant. In case of phytochemical analysis methanolic extract of leaves and bark showed highest phenolic and flavonoids contents. n-Hexane and ethyl acetate extracts of stem and roots exhibited more than 90% mortality with LD50 ranges between 1-25 µg/mL when studied by brine shrimp lethality assay. n-Hexane and ethyl acetate extracts of roots and stem also showed antiproliferative activity against human breast cancer MCF-7 cell line with IC50 values ranges between 12.10-14.20 µg/mL. Most of the extracts displayed moderately high antibacterial and antifungal activities. The n-hexane extract of roots showed antidiabetic activity with 60.80 ± 0.20% inhibition of alpha-amylase. In sum, these preliminary results will be useful for further compound isolation from selected plant parts for the discovery of antibacterial, antidiabetic, and anticancer lead candidates.

Optimization, Characterization, and Antibacterial Activity of Copper Nanoparticles Synthesized Using Senna didymobotrya Root Extract

The economic burden and high mortality associated with multidrug-resistant bacteria is a major public health concern. Biosynthesized copper nanoparticles (CuNPs) could be a potential alternative to combat bacterial resistance to conventional medicine. This study for the first time aimed at optimizing the synthesis conditions (concentration of copper ions, temperature, and pH) to obtain the smallest size of CuNPs, characterizing and testing the antibacterial efficacy of CuNPs prepared from Senna didymobotrya (S. didymobotrya) roots. Extraction was done by the Soxhlet method using methanol as the solvent. Gas chromatography-mass spectrometry (GC-MS) analysis was performed to identify compounds in S. didymobotrya root extracts. Box–Behnken design was used to obtain optimal synthesis conditions as determined using a particle analyzer. Characterization was done using ultraviolet-visible (UV-Vis), particle size analyzer, X-ray diffraction, zeta potentiometer, and Fourier transform infrared (FT-IR). Bioassay was conducted using the Kirby–Bauer disk diffusion susceptibility test. The major compounds identified by GC-MS in reference to the NIST library were benzoic acid, thymol, N-benzyl-2-phenethylamine, benzaldehyde, vanillin, phenylacetic acid, and benzothiazole. UV-Vis spectrum showed a characteristic peak at 570 nm indicating the formation of CuNPs. The optimum synthesis conditions were temperature of 80°C, pH 3.0, and copper ion concentration of 0.0125 M. The FT-IR spectrum showed absorptions in the range 3500–3400 cm−1 (N-H stretch), 3400–2400 cm−1 (O-H stretch), and 988–830 cm−1 (C-H bend) and peak at 1612 cm−1 (C=C stretch), and 1271 cm−1 (C-O bend). Cu nanoparticle sizes were 5.55–63.60 nm. The zeta potential value was −69.4 mV indicating that they were stable. The biosynthesized nanoparticles exhibited significant antimicrobial activity on Escherichia coli and Staphylococcus aureus with the zone of inhibition diameters of 26.00 ± 0.58 mm and 30.00 ± 0.58 mm compared to amoxicillin clavulanate (standard) with inhibition diameters of 20 ± 0.58 mm and 28.00 ± 0.58 mm, respectively.

Reproducibility challenges in the search for antibacterial compounds from nature

Background

Reproducibility of reported antibacterial activities of plant extracts has long remained questionable. Although plant-related factors should be well considered in serious pharmacognostic research, they are often not addressed in many research papers. Here we highlight the challenges in reproducing antibacterial activities of plant extracts.

Methods

Plants with reported antibacterial activities of interest were obtained from a literature review. Antibacterial activities against Escherichia coli and Klebsiella pneumoniae were tested using extracts’ solutions in 10% DMSO and acetone. Compositions of working solutions from both solvents were established using LC-MS analysis. Moreover, the availability of details likely to affect reproducibility was evaluated in articles which reported antibacterial activities of studied plants.

Results

Inhibition of bacterial growth at MIC of 256–1024 μg/mL was observed in only 15.4% of identical plant species. These values were 4–16-fold higher than those reported earlier. Further, 18.2% of related plant species had MICs of 128–256 μg/mL. Besides, 29.2% and 95.8% of the extracts were soluble to sparingly soluble in 10% DMSO and acetone, respectively. Extracts’ solutions in both solvents showed similar qualitative compositions, with differing quantities of corresponding phytochemicals. Details regarding seasons and growth state at collection were missing in 65% and 95% of evaluated articles, respectively. Likewise, solvents used to dissolve the extracts were lacking in 30% of the articles, whereas 40% of them used unidentified bacterial isolates.

Conclusion

Reproducibility of previously reported activities from plants’ extracts is a multi-factorial aspect. Thus, collective approaches are necessary in addressing the highlighted challenges.

A Systematic Review of Plants With Antibacterial Activities: A Taxonomic and Phylogenetic Perspective

Background: Antimicrobial resistance represents a serious threat to human health across the globe. The cost of bringing a new antibiotic from discovery to market is high and return on investment is low. Furthermore, the development of new antibiotics has slowed dramatically since the 1950s’ golden age of discovery. Plants produce a variety of bioactive secondary metabolites that could be used to fuel the future discovery pipeline. While many studies have focused on specific aspects of plants and plant natural products with antibacterial properties, a comprehensive review of the antibacterial potential of plants has never before been attempted.

Objectives: This systematic review aims to evaluate reports on plants with significant antibacterial activities.

Methods: Following the PRISMA model, we searched three electronic databases: Web of Science, PubMed and SciFinder by using specific keywords: “plant,” “antibacterial,” “inhibitory concentration.”

Results: We identified a total of 6,083 articles published between 1946 and 2019 and then reviewed 66% of these (4,024) focusing on articles published between 2012 and 2019. A rigorous selection process was implemented using clear inclusion and exclusion criteria, yielding data on 958 plant species derived from 483 scientific articles. Antibacterial activity is found in 51 of 79 vascular plant orders throughout the phylogenetic tree. Most are reported within eudicots, with the bulk of species being asterids. Antibacterial activity is not prominent in monocotyledons. Phylogenetic distribution strongly supports the concept of chemical evolution across plant clades, especially in more derived eudicot families. The Lamiaceae, Fabaceae and Asteraceae were the most represented plant families, while Cinnamomum verum, Rosmarinus vulgaris and Thymus vulgaris were the most studied species. South Africa was the most represented site of plant collection. Crude extraction in methanol was the most represented type of extraction and leaves were the main plant tissue investigated. Finally, Staphylococcus aureus was the most targeted pathogenic bacteria in these studies. We closely examine 70 prominent medicinal plant species from the 15 families most studied in the literature.

Conclusion: This review depicts the current state of knowledge regarding antibacterials from plants and provides powerful recommendations for future research directions.

Ethnoveterinary for food-producing animals and related food safety issues: A comprehensive overview about terpenes

Alternatives to the use of conventional veterinary drugs in food-producing animals have gained attention, such as the use of natural products (NPs), mainly to soften the risks to the animal, the environment, and consumer's health. Although NPs have consistent advantages over conventional drugs, they cannot be considered risk free under food safety matters. In this way, this document presents a comprehensive overview of the importance of considering both the pharmacological and toxicological properties of the constituents of a NP from plants intending the standardization and regulation of its use in food-producing animals. Terpenes are the most diverse class of natural substances present in NP of vegetal origin with a broad range of biological activities that can be explored in veterinary science; however, certain plants and terpenes also have significant toxic effects, a fact that can harm the health of animals and consequently generate economic losses and risks for humans. In this context, this review gathered scientific data of vegetal species of importance to ethnoveterinary for food-producing animals, which produce terpenes, its biological effects, and their implications on food safety issues for consumers. For this, more than 300 documents were selected from different online scientific databases. The present data and discussion may contribute to the rational commercial exploration of this class of NPs in veterinary medicine.

African Plant-Based Natural Products with Antivirulence Activities to the Rescue of Antibiotics

The worldwide emergence of antibiotic-resistant bacteria and the thread of widespread superbug infections have led researchers to constantly look for novel effective antimicrobial agents. Within the past two decades, there has been an increase in studies attempting to discover molecules with innovative properties against pathogenic bacteria, notably by disrupting mechanisms of bacterial virulence and/or biofilm formation which are both regulated by the cell-to-cell communication mechanism called ‘quorum sensing’ (QS). Certainly, targeting the virulence of bacteria and their capacity to form biofilms, without affecting their viability, may contribute to reduce their pathogenicity, allowing sufficient time for an immune response to infection and a reduction in the use of antibiotics. African plants, through their huge biodiversity, present a considerable reservoir of secondary metabolites with a very broad spectrum of biological activities, a potential source of natural products targeting such non-microbicidal mechanisms. The present paper aims to provide an overview on two main aspects: (i) succinct presentation of bacterial virulence and biofilm formation as well as their entanglement through QS mechanisms and (ii) detailed reports on African plant extracts and isolated compounds with antivirulence properties against particular pathogenic bacteria.

Antioxidant, Antimicrobial, and Anticancer Effects of Anacardium Plants: An Ethnopharmacological Perspective

Anacardium plants have received increasing recognition due to its nutritional and biological properties. A number of secondary metabolites are present in its leaves, fruits, and other parts of the plant. Among the diverse Anacardium plants' bioactive effects, their antioxidant, antimicrobial, and anticancer activities comprise those that have gained more attention. Thus, the present article aims to review the Anacardium plants' biological effects. A special emphasis is also given to their pharmacological and clinical efficacy, which may trigger further studies on their therapeutic properties with clinical trials.

New approach in the characterization of bioactive compounds isolated from Calycotome spinosa (L.) Link leaves by the use of negative electrospray ionization LITMSn, LC-ESI-MS/MS, as well as NMR analysis

Two novel compounds were isolated for the first time from Calycotome spinosa (L.) Link, an alkaloid 5-Hydroxy-1H-indole (4) and a cyclitol D-pinitol (5), together with the three well-known flavonoids; Chrysin-7-O-(β-D-glucopyranoside) (1), Chrysin-7-O-β-D-(6″-acetyl)glycopyranoside (2) and Apigenin-7-O-β-D-glycopyranoside (3). The chemical structures of the isolated compounds were elucidated by spectroscopic data and mass spectrometric analyses; including a fresh approach 1D-NMR, 2D-NMR with LC-ESI-MS/MS. In this study, the new compound (4) that has been obtained from the leaves MeOH extract presented the best radical scavenging activity (DPPH) (IC₅₀ < 10 µg/mL) compared to the standard butylated hydroxytoluene (BHT, IC₅₀ = 34.73 ± 0.23 μg/mL) and showed the highest total antioxidant capacity (TAC = 985.54 ± 0.13 mg AAE/g extract) in contrast to ascorbic acid (TAC = 905.95 ± 0.07 mg AAE/g extract). Furthermore, the strongest reducing power (EC₅₀ = 344.82 ± 0.02 µg/mL), as well as the remarkable scavenging potential by ABTS assay (IC₅₀ = 7.8 ± 0.43 µg/mL), were exhibited by the same composite (4). Followed by the methanol crude extract and the compound (3) that also showed a potent antioxidant (DPPH; IC₅₀ = 41.04 ± 0.15 and 47.36 ± 0.21 µg/mL, TAC; 671.02 ± 0.21 and 608.67 ± 0.34 mg AAE/g extract, FRAP; EC₅₀ = 763.73 ± 0.32 and 814.61 ± 0.31 µg/mL, ABTS; IC₅₀ = 19.18 ± 0.06 and 63.72 ± 0.64 µg/mL, respectively), but less than the previous samples. On the opposite side, compound (5) had the lowest activity, in which its values were less interesting to determine. Moreover, compound (4) has equally exerted an attractive antibacterial activity against Staphylococcus aureus (ATTC-25923), Pseudomonas aeruginosa (ATTC- 27853) and Salmonella abony (NCTC 6017), as measured by the disc diffusion assay, with inhibition zones of 16 ± 0.5, 9.83 ± 0.29 and 8 ± 0.28 mm, in that order. To the best of our knowledge, 5-Hydroxy-1H-indole was isolated from plants for the second time in our current work. Thus, the obtained results from this investigation propose that the leaves of C. spinosa are a rich natural source for value molecules as potential antioxidants and antimicrobial agents for best human health.

Cytogenotoxic and mutagenic profiling of cashew nut shell liquids and cardanol

Background

Cashew and its compounds have many important biological effects. This study is aimed at evaluating genotoxic and mutagenic effects of natural cashew nut shell liquid (nCNSL) and industrial cashew nut shell liquid (iCNSL) and a major component of iCNSL called Cardanol.

Methods

Test samples were undergone for comet assay and micronucleus tests inSwissalbino mice. Animals were orally treated with 17.37, 34.75 and 69.5 mg/kg of the test substances taking distilled water (10 mL/kg; DW) and cyclophosphamide (50 mg/kg) as negative (NC) and positive (PC) controls, respectively.

Results

The results suggest that nCNSL at 34.7 and 69.5 mg/kg and Cardanol at all tested doses induced significant genotoxic effects to the female mouse bone marrow cells, while iCNSL did not. Both nCNSL and iCNSL as well as Cardanol did not show mutagenic and cytotoxic effects. All the test samples also showed DNA repair capacity at low dose.

Conclusion

Cashew nut shell liquids and Cardanol showed genotoxic effects at high dose, but DNA repair, non-mutagenic and non-cytotoxic effects at low dose.

Leveraging phytochemicals: the plant phylogeny predicts sources of novel antibacterial compounds

Aim

The goal of this study was to use phylogenetic evidence to determine plant families with high representation of antibacterial activity and identify potential sources to focus on for antibacterial drug discovery.

Materials & methods

We reconstructed the molecular phylogeny of plant taxa with antibacterial activity and mapped antibacterial mechanisms of action on the phylogeny.

Results

The phylogeny highlighted seven plant families (Combretaceae, Cupressaceae, Fabaceae, Lamiaceae, Lauraceae, Myrtaceae and Zingiberaceae) with disproportionately represented antibacterial activity. Phytochemicals produced were primarily involved in the disruption of the bacterial cell wall/membrane and inhibition of quorum sensing/biofilm production.

Conclusion

The study provides phylogenetic evidence of seven plant families that should be examined as promising leads for novel antibacterial development.

Bioactive compounds from the African medicinal plant Cleistochlamys kirkii as resistance modifiers in bacteria

Cleistochlamys kirkii (Benth) Oliv. (Annonaceae) is a medicinal plant traditionally used in Mozambique to treat infectious diseases. The aim of this study was to find resistance modifiers in C. kirkii for Gram-positive and Gram-negative model bacterial strains. One of the most important resistance mechanisms in bacteria is the efflux pump-related multidrug resistance. Therefore, polycarpol (1), three C-benzylated flavanones (2-4), and acetylmelodorinol (5) were evaluated for their multidrug resistance-reverting activity on methicillin-susceptible and methicillin-resistant Staphylococcus aureus and Escherichia coli AG100 and AG100 A strains overexpressing and lacking the AcrAB-TolC efflux pump system. The combined effects of antibiotics and compounds (2 and 4) were also assessed by using the checkerboard microdilution method in both S. aureus strains. The relative gene expression of the efflux pump genes was determined by real-time reverse transcriptase quantitative polymerase chain reaction. The inhibition of quorum sensing was also investigated. The combined effect of the antibiotics and compound 2 or 4 on the methicillin-sensitive S. aureus resulted in synergism. The most active compounds 2 and 4 increased the expression of the efflux pump genes. These results suggested that C. kirkii constituents could be effective adjuvants in the antibiotic treatment of infections.

Polarity based characterization of biologically active extracts of Ajuga bracteosa Wall. ex Benth. and RP-HPLC analysis

BACKGROUND

The concept of botanical therapeutics has revitalized due to wide importance of plant derived pharmaceuticals. Therefore, the ameliorative characteristics of Ajuga bracteosa were studied.

METHODS

Total phenolic content, flavonoid content, antioxidant capacity, reducing power and free-radical scavenging activity were determined colorimetrically. Specific polyphenols were quantified by RP-HPLC analysis. Preliminary cytotoxicity was tested using brine shrimp lethality assay while antiproliferative activity against THP-1 and Hep-G2 cell lines was determined by MTT and SRB protocols respectively. Antileishmanial potential was assessed via MTT colorimetric method. To investigate antidiabetic prospect, α-amylase inhibition assay was adopted whereas disc diffusion method was used to detect likely protein kinase inhibitory, antibacterial and antifungal activities.

RESULTS

Among fifteen different extracts, maximum total phenolic content (10.75 ± 0.70 μg GAE/mg DW), total reducing power (23.90 ± 0.70 μg AAE/mg DW) and total antioxidant capacity (11.30 ± 0.80 μg AAE/mg DW) were exhibited by methanol extract with superlative percent extract recovery (17.50 ± 0.80% w/w). Chloroform-methanol extract demonstrated maximum flavonoid content (4.10 ± 0.40 μg QE/mg DW) and ethanol extract exhibited greatest radical scavenging activity (IC50 14.40 ± 0.20 μg/ml). RP-HPLC based quantification confirmed polyphenols such as pyrocatechol, gallic acid, resorcinol, catechin, chlorogenic acid, caffeic acid, syringic acid, p-coumaric acid, ferulic acid, vanillic acid, coumarin, sinapinic acid, trans-cinnamic acid, rutin, quercetin and kaempferol. The brine shrimp lethality assay ranked 78.60% extracts as cytotoxic (LC50 ≤ 250 μg/ml) whereas significant THP-1 inhibition was shown by methanol-acetone extract (IC50 4.70 ± 0.43 μg/ml). The antiproliferative activity against Hep-G2 hepatoma cancer cell line was demonstrated by n-hexane, ethylacetate and methanol-distilled water (IC50 8.65-8.95 μg/ml) extracts. Methanol extract displayed prominent protein kinase inhibitory activity (MIC 12.5 μg/disc) while n-hexane extract revealed remarkable antileishmanial activity (IC50 4.69 ± 0.01 μg/ml). The antidiabetic potential was confirmed by n-hexane extract (44.70 ± 0.30% α-amylase inhibition at 200 μg/ml concentration) while a moderate antibacterial and antifungal activities were unveiled.

CONCLUSION

The variation in biological spectrum resulted due to use of multiple solvent systems for extraction. We also deduce that the valuable information gathered can be utilized for discovery of anticancer, antileishmanial, antioxidant and antidiabetic bioactive lead candidates.

Acacia karroo Hayne: Ethnomedicinal uses, phytochemistry and pharmacology of an important medicinal plant in southern Africa

Acacia karroo (A. karroo) has been used as herbal medicine by the indigenous people of southern Africa for several centuries. The potential of A. karroo as herbal medicine, its associated phytochemistry and biological activities are reviewed. The extensive literature survey revealed that A. karroo is traditionally used to treat or manage 32 and five human and animal diseases and ailments, respectively. The species is used as herbal medicine for diseases and ailments such as colds, diarrhoea, dysentery, flu, malaria, sexually transmitted infections (STIs), wounds, and also as colic and ethnoveterinary medicine. Multiple classes of phytochemicals such as flavonoids, phenols, phytosterols, proanthocyanidin, tannin, terpenes as well as several minerals have been identified from leaves and roots of A. karroo. Scientific studies on A. karroo indicate that it has a wide range of pharmacological activities which include antibacterial, antifungal, antigonococcal, antihelmintic, antilisterial, antimalarial, antimycobacterial, antioxidant, HIV-1 reverse transcriptase, anti-inflammatory and analgesic. A. karroo has a lot of potential as a possible source of pharmaceutical products for the treatment of a wide range of both human and animal diseases and ailments. Future research should focus on the mechanisms of action of the different plant parts used as herbal medicines, isolated compounds, their efficacy, toxicity and clinical relevance.

Adverse Effects of Hydroalcoholic Extracts and the Major Components in the Stems of Impatiens balsamina L. on Caenorhabditis elegans

Impatiens balsamina L. (Balsaminaceae), an annual herb found throughout China, has been extensively used in traditional Chinese medicine (TCM). However, our knowledge regarding the adverse effects of I. balsamina in vivo is very limited. In this present study, the nematode Caenorhabditis elegans model was employed to fully assess the adverse effects of hydroalcoholic (EtOH 55%) extracts of I. balsamina stems (HAEIBS) in vivo. After exposure to 10 mg/mL HAEIBS, the major organism-level endpoints of C. elegans of percent survival, frequency of head thrash and body bends, and reproduction had decreased by 24%, 30%, and 25%, respectively. The lifespan of C. elegans was also greatly reduced after HAEIBS exposure compared to the controls. The active compounds in HAEIBS were separated using high speed countercurrent chromatograph (HSCCC) and characterized by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). Two compounds, lawsone and 2-methoxy-1,4-naphthoquinone (MNQ), and their adverse effects were then more thoroughly detailed in this study. It was found that lawsone is the major toxin in HAEIBS with a higher toxicity than MNQ in terms of negative impact on C. elegans mortality, locomotion, reproduction, and lifespan. Our data also suggests that the C. elegans model may be useful for assessing the possible toxicity of other Chinese medicines, plant extracts, and/or compounds.

Antimycobacterial activity of medicinal plants used by the Mayo people of Sonora, Mexico

ETHNOPHARMACOLOGICAL RELEVANCE

Tuberculosis (TB) is an infectious disease mainly caused by Mycobacterium tuberculosis (Mtb), which generates 9 million new cases worldwide each year. The Mayo ethnicity of southern Sonora, Mexico is more than 2000 years old, and the Mayos possess extensive knowledge of traditional medicine.

AIMS OF THE STUDY

To evaluate the antimycobacterial activity levels of extracts of medicinal plants used by the Mayos against Mtb and Mycobacterium smegmatis (Msm) in the treatment of TB, respiratory diseases and related symptoms.

MATERIALS AND METHODS

A total of 34 plant species were collected, and 191 extracts were created with n-hexane, dichloromethane, ethyl acetate (EtOAc), methanol and water. Their minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined against Mtb H37Rv using the microplate alamar blue assay (MABA) and against Msm using the resazurin microplate assay (REMA) at 6 and 2 days of exposure, respectively, and at concentrations of 250-1.9µg/mL (n-hexane extracts) and 1000-7.81µg/mL (extracts obtained with dichloromethane, EtOAc, methanol and water).

RESULTS

Rhynchosia precatoria (Willd.) DC. (n-hexane root extract), Euphorbia albomarginata Torr. and A. Gray. (EtOAc shoot extract) and Helianthus annuus L. (n-hexane stem extract) were the most active plants against Mtb H37Rv, with MICs of 15.6, 250, 250µg/mL and MBCs of 31.25, 250, 250µg/mL, respectively. R. precatoria (root) was the only active plant against Msm, with MIC and MBC values of ≥250µg/mL. None of the aqueous extracts were active.

CONCLUSIONS

This study validates the medicinal use of certain plants used by the Mayo people in the treatment of TB and related symptoms. R. precatoria, E. albomarginata and H. annuus are promising plant sources of active compounds that act against Mtb H37Rv. To our knowledge, this is the first time that their antimycobacterial activity has been reported. Crude extracts obtained with n-hexane, EtOAc and dichloromethane were the most active against Mtb H37Rv.

Medicinal Plants Used in Mali for the Treatment of Malaria and Liver Diseases

Today, ethno-pharmacology is a very important resource in order to discover new therapies for the current diseases. Moreover, another good justification for the ethno-pharmacological approach is to obtain new, effective, less expensive and simple therapies, limiting at the same time the cost of pharmaceutical research. Two major anti-malarial drugs widely used today, i.e. quinine and artemisinin, came respectively from Peruvian and Chinese ancestral treatments reported in the traditional medicines. In this contest, there is an urgent need for the discovery of new drugs, due to the critical epidemiological situation of this disease and to the growth of resistances. In Mali, malaria and liver diseases remain one of the leading public health problems. Many medicinal plants are often used, in local traditional medicine, for the treatment at the same time of malaria and liver diseases, including hepatic syndromes, jaundice, hepatitis and other hepatic disorders. Moreover, in the local language Bamanan, the word “ Sumaya” is used both for malaria and some liver diseases. In addition, we noted that some of the improved traditional phytomedicines produced by the Department of Traditional Medicine are prescribed by modern doctors both for malaria and liver diseases. In this review, pharmacological, toxicological and phytochemical data on Argemone mexicana L. (Papaveraceae), Cochlospermum tinctorium Perr. ex A. Rich (Cochlospermaceae), Combretum micranthum G.Don (Combretaceae), Entada africana Guillet Perr. (Mimosaceae), Erythrina senegalensis A. DC (Fabaceae), Mitragyna inermis (Willd) Kuntze (Rubiaceae), Nauclea latifolia Smith syn. Sarcocephalus latifolius (Smith) Bruce (Rubiaceae), Securidaca longepedunculata Fresen (Polygalaceae), Trichilia emetica Vahl. (Meliaceae), and Vernonia colorata (Willd) Drake (Asteraceae) are reported. Some of the collected data could be used to improve the actual herbal drugs and to propose new phytomedicines for the management of malaria and liver diseases.

Cleistochlamys kirkii chemical constituents: Antibacterial activity and synergistic effects against resistant Staphylococcus aureus strains

ETHNOPHARMACOLOGICAL RELEVANCE

Cleistochlamys kirkii (Benth) Oliv., (Annonaceae) is a medicinal plant traditionally used in Mozambique to treat infectious diseases.

AIMS OF THE STUDY

To find antibacterial lead compounds from C. kirkii and provide scientific validation for its use in traditional medicine.

MATERIALS AND METHODS

Through bioassay-guided fractionation, nine compounds (1-9), with different scaffolds, were isolated from the methanol extract of C. kirkii whose structures were identified by spectroscopic methods. Compounds 1-9 were evaluated for their in vitro antibacterial activity against a panel of eight Gram-positive, including five drug-resistant strains of Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, and two Gram-negative bacteria strains. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. A chemosensitization assay, using the checkerboard method, was also performed in order to evaluate the type of interaction of compounds with antibiotics/compounds against two S. aureus resistant strains (ATCC 9144 and CIP 106760) and a susceptible strain (ATCC 6538).

RESULTS

Dichamanetin (3), a rare C-benzylated flavanone, was very active against all the Gram-positive strains tested, displaying MIC values in the range of 1-7.5 μg/mL. The C-benzylated flavanones chamanetin (1), isochamanetin (2), and the α,β-unsaturated lactone (-)-cleistenolide (6) also showed relevant antibacterial activity against some of the Gram-positive strains assayed. Compounds 4, 5, and 7-9 have shown no significant activity at the concentration ranges tested. In the combination with antibiotics, polycarpol (8) (MIC 125 μg/mL) showed a strong synergistic effect against the methicillin-resistant S. aureus ATCC 9144. When combined with oxacillin (MIC 125 μg/mL), compound 8 reduced the MIC to 1.5 μg/mL (FICI=0.11). Similarly, it reduced the MIC of amoxicillin (MIC 250 μg/mL) to 7.5 μg/mL (FICI=0.18). Synergy was also obtained when this compound was combined with both β-lactam antibiotics (FICI=0.30) and with vancomycin (FICI=0.24) against vancomycin-intermediate S. aureus (VISA) CIP 106760. Remarkable, compound 8 was also able to reduce synergistically the MIC value of dichamanetin (3) (FICI=0.18) against this strain.

CONCLUSIONS

These results suggested that C. kirkii constituents may be valuable as a leads for restoring antibiotic activity against resistant S. aureus strains.

Enhancing activity of antibiotics against Staphylococcus aureus: Zanthoxylum capense constituents and derivatives

Six compounds (1-6), isolated from the methanol extract of the roots of the African medicinal plant Zanthoxylum capense Thunb. (Rutaceae), and seven ester derivatives (7-13) were evaluated for their antibacterial activities and modulatory effects on the MIC of antibiotics (erythromycin, oxacillin, and tetracycline) and ethidium bromide (EtBr) against a Staphylococcus aureus reference strain (ATCC 6538). Using the same model, compounds 1-13 were also assessed for their potential as efflux pump inhibitors by a fluorometric assay that measures the accumulation of the broad range efflux pump substrate EtBr. Compounds 8 and 11 were further evaluated for their antibacterial, modulatory and EtBr accumulation effects against four additional S. aureus strains, which included two clinical methicillin-resistant S. aureus (MRSA) strains. Compounds (1-13) have not shown antibacterial activity at the concentration ranges tested. When evaluated against S. aureus ATCC 6538, oxychelerythrine (1) a benzophenanthridine alkaloid, showed the highest modulatory activity enhancing the susceptibility of this strain to all the tested antibiotics from two to four-fold. Ailanthoidiol diacetate (8) and ailanthoidiol di-2-ethylbutanoate (11) were also good modulators when combined with EtBr, increasing the bacteria susceptibility by four and two-fold, respectively. In the EtBr accumulation assay, using ATCC 6538 strain, the phenylpropanoid (+)-ailanthoidiol (6) and most of its ester derivatives (8-11) exhibited higher activity than the positive control verapamil. The highest effects were found for compounds 8 and 11 that also increased the accumulation of EtBr, using S. aureus ATCC 25923 as model. Furthermore, both compounds (8, 11) were able to enhance the ciprofloxacin activity against the MRSA clinical strains tested, causing a reduction of the antibiotic MIC values from two to four-fold. The EtBr accumulation assay revealed that this modulation activity was not due to an inhibition of efflux pumps mechanism. These results suggested that Z. capense constituents may be valuable as leads for restoring antibiotic activity against MRSA strains.

A new antibacterial benzophenone glycoside from Psidium guajava (Linn.) leaves

Bioactivity-guided fractionation of methanol extract from the leaves of Psidium guajava L. (Myrtaceae) yielded a new benzophenone glycoside, Guajaphenone A (2) together with two known compounds, Garcimangosone D (1) and Guaijaverin (3). Their structures were elucidated by analysis of spectroscopic data including 1D and 2D NMR and electrospray ionisation mass spectrometry (ESI-MS). The isolated compounds were screened against standard strains of Gram-positive and Gram-negative bacteria using broth dilution assay method, and the MIC values determined and compared with reference antibiotic ceftriaxone. They were found to have significant antibacterial activities against Escherichia coli and Staphylococcus aureus with all of them showing better activities against S. aureus, but displaying weaker activities, in comparison to ceftriaxone. However, despite reduced effect of these compounds against the organisms, this work opens the perspective to use these molecules as 'leads' for the design of novel and selective drug candidates for some tropical infectious diseases.

Toxicology of some important medicinal plants in southern Africa

Africa is home to two major floral kingdoms: the Paleotropical kingdom of central Africa and the Capensis kingdom of the Western Cape province of South Africa, the latter of which consists of approximately 10,000 species, representing about 20% of Africa's floral 'gold mine', better known as the Cape herbal medicine. Needless to say, such rich flora comes with numerous plants with a potential to cause poisoning to humans. This review document reports important toxic medicinal plants and their toxic ingredients for plant species resident in the southern African region. These include important medicinal uses and pharmacological properties ranging from antimicrobial, antiviral, anticancer, anti-inflammatory as well as those that are used as aphrodisiacs and for maternal health care.

Traditional use of medicinal plants in south-central Zimbabwe: review and perspectives

BACKGROUND

Traditional medicine has remained as the most affordable and easily accessible source of treatment in the primary healthcare system of resource poor communities in Zimbabwe. The local people have a long history of traditional plant usage for medicinal purposes. Despite the increasing acceptance of traditional medicine in Zimbabwe, this rich indigenous knowledge is not adequately documented. Documentation of plants used as traditional medicines is needed so that the knowledge can be preserved and the utilized plants conserved and used sustainably. The primary objective of this paper is to summarize information on traditional uses of medicinal plants in south-central Zimbabwe, identifying research gaps and suggesting perspectives for future research.

METHODS

This study is based on a review of the literature published in scientific journals, books, reports from national, regional and international organizations, theses, conference papers and other grey materials.

RESULTS

A total of 93 medicinal plant species representing 41 families and 77 genera are used in south-central Zimbabwe. These plant species are used to treat 18 diseases and disorder categories, with the highest number of species used for gastro-intestinal disorders, followed by sexually transmitted infections, cold, cough and sore throat and gynaecological problems. Shrubs and trees (38% each) were the primary sources of medicinal plants, followed by herbs (21%) and climbers (3%). The therapeutic claims made on medicinal plants documented in south-central Zimbabwe are well supported by literature, with 82.8% of the plant species having similar applications in other regions of Zimbabwe as well as other parts of the world and 89.2% having documented biological and pharmacological properties.

CONCLUSION

This study illustrates the importance of traditional medicines in the treatment and management of human diseases and ailments in south-central Zimbabwe. Traditional medicines still play an important role in meeting basic health care of local communities in Zimbabwe.

Antioxidant effect of Stryphnodendron rotundifolium Martius extracts from Cariri-Ceará State (Brazil): potential involvement in its therapeutic use

Stryphnodendron rotundifolium is a phytotherapic used in the northeast of Brazil for the treatment of inflammatory processes which normally are associated with oxidative stress. Consequently, we have tested the antioxidant properties of hydroalcoholic (HAB) and aqueous extracts (AB) from the bark and aqueous extract (AL) from the leaves of Stryphnodendron rotundifolium to determine a possible association between antioxidant activity and the popular use of this plant. Free radical scavenger properties were assessed by the quenching of 1',1'-diphenil-2-picrylhydrazyl (DPPH) and the calculated IC(50) were: HAB = 5.4 ± 0.7, AB = 12.0 ± 2.6, and AL = 46.3 ± 12.3 µg/mL. Total phenolic contents were: HAB = 102.7 ± 2.8, AB = 114.4 ± 14.6, and AL = 93.8 ± 9.1 µg/mg plant). HPLC/DAD analyses indicated that gallic acid, catechin, rutin and caffeic acid were the major components of the crude extracts of S. rotundifolium. Plant extracts inhibited Fe(II)-induced lipid peroxidation in brain homogenates. Iron chelation was also investigated and only HBA exhibited a weak activity. Taken together, the results suggest that S. rotundifolium could be considered an effective agent in the prevention of diseases associated with oxidative stress.