Antibacterial activities of Fagara macrophylla, Canarium schweinfurthii, Myrianthus arboreus, Dischistocalyx grandifolius and Tragia benthamii against multi-drug resistant Gram-negative bacteria

Chemical profiling, toxicity assessment, anti-diarrhoeal, anti-inflammatory and antinociceptive activities of Canarium schweinfurthii Engl. (Burseraceae) bark in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The bark of Canarium schweinfurthii is used in ethnomedicine for the treatment of diabetes, pain, malaria, fever and diarrhoea.

AIM OF THE STUDY

The chemical phytoconstituents, antidiarrheal, anti-inflammatory and antinociceptive effects and safety profile of the aqueous extract of Canarium schweinfurthii bark (AECSB) were investigated.

MATERIALS AND METHODS

Gas chromatography-mass spectrometry (GC-MS) was used to analyse the phytochemical composition. In the acute toxicity test, AECSB were administered up to 2 g/kg by oral gavage. For the subacute toxicity test (28 days), rats in group 1 (control) received no AECSB, while rats in groups 2-4 were administered different doses of AECSB. Charcoal meal transit and castor oil-induced diarrhoea models were used to study the antidiarrheal effect, while egg albumin/carrageenan and acetic acid/tail immersion models were used for the anti-inflammatory and antinociceptive studies, respectively. With the exception of the acute toxicity experiment, AECSB was administered orally at doses of 200, 400 and 800 mg/kg.

RESULTS

Bioactive phytoconstituents identified include p-cymene, δ-terpinene, linalool and phytol. No adverse effects or mortality were observed in acute and subacute studies. Treatment with AECSB (28 days) had no significant effect on organ weight, biochemical, hematologic and histopathologic parameters compared to the control groups (p > 0.05). Comparable antidiarrheal and antinociceptive effects were observed in both AECSB- and standard drug-treated groups, while the 400 and 800 mg/kg AECSB-treated groups showed remarkable anti-inflammatory effects compared to the standard drug-treated and control groups (p < 0.05).

CONCLUSION

AECSB has antidiarrheal, antinociceptive and anti-inflammatory effects and can be safely used for therapeutic purposes.

Disruption of Biofilm Formation and Quorum Sensing in Pathogenic Bacteria by Compounds from Zanthoxylum Gilletti (De Wild) P.G. Waterman

Microbial resistance is facilitated by biofilm formation and quorum-sensing mediated processes. In this work, the stem bark (ZM) and fruit extracts (ZMFT) of Zanthoxylum gilletii were subjected to column chromatography and afforded lupeol (1), 2,3-epoxy-6,7-methylenedioxyconiferyl alcohol (3), nitidine chloride (4), nitidine (7), sucrose (6) and sitosterol-β-D-glucopyranoside (2). The compounds were characterized using MS and NMR spectral data. The samples were evaluated for antimicrobial, antibiofilm and anti-quorum sensing activities. Highest antimicrobial activity was exhibited by compounds 3, 4 and 7 against Staphylococcus aureus (MIC 200 µg/mL), compounds 3 and 4 against Escherichia coli (MIC = 100 µg/mL) and compounds 4 and 7 against Candida albicans (MIC = 50 µg/mL). At MIC and sub-MIC concentrations, all samples inhibited biofilm formation by pathogens and violacein production in C. violaceum CV12472 except compound 6. Good disruption of QS-sensing in C. violaceum revealed by inhibition zone diameters were exhibited by compounds 3 (11.5 ± 0.5 mm), 4 (12.5 ± 1.5 mm), 5 (15.0 ± 0.8 mm), 7 (12.0 ± 1.5 mm) as well as the crude extracts from stem barks (16.5 ± 1.2 mm) and seeds (13.0 ± 1.4 mm). The profound inhibition of quorum sensing mediated processes in test pathogens by compounds 3, 4, 5 and 7 suggests the methylenedioxy- group that these compounds possess as the possible pharmacophore.

Bioactive Molecules from Myrianthus arboreus, Acer rubrum, and Picea mariana Forest Resources

Forest trees are the world's most important renewable natural resources in terms of their dominance among other biomasses and the diversity of molecules that they produce. Forest tree extractives include terpenes and polyphenols, widely recognized for their biological activity. These molecules are found in forest by-products, such as bark, buds, leaves, and knots, commonly ignored in forestry decisions. The present literature review focuses on in vitro experimental bioactivity from the phytochemicals of Myrianthus arboreus, Acer rubrum, and Picea mariana forest resources and by-products with potential for further nutraceutical, cosmeceutical, and pharmaceutical development. Although these forest extracts function as antioxidants in vitro and may act on signaling pathways involved in diabetes, psoriasis, inflammation, and skin aging, much still remains to be investigated before using them as therapeutic candidates, cosmetics, or functional foods. Traditional forest management systems focused on wood must evolve towards a holistic approach, allowing the use of these extractives for developing new value-added products.

Wound Healing Potential of an Oleoresin Essential Oil Chemotype from Canarium schweinfurthii Engl

This study was conducted to investigate the chemical composition of essential oil (EO) extracted from an oleoresin of Canarium schweinfurthii widespread in the Gabonese tropical forest. A great variability in the chemical composition of EO was observed, among which a chemical profile rich in terpinolene and α-phellandrene (31.2 and 21.8%, respectively), was found and tested as a natural active ingredient for topical applications. After the evaluation of eye and skin irritancy and sensitization potentials of EO on in vitro and in chemico models, the in vitro modulating potential on a model of wound re-epithelialization was assessed. The terpinolene and α-phellandrene-rich chemotype have been proven to accelerate wound healing in a dose-dependent manner (concentration range from 1.8 to 9.0 μg/mL). In addition, the ability of this EO to modulate the pro-inflammatory response in human keratinocytes stimulated by UVB was observed in vitro by the reduction in levels of interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNF-α), suggesting a possible implication during the inflammation phase of wound healing. Despite the high variability in EO composition, a method of solid-phase microextraction (SPME) of the oleoresin headspace is proposed for the in situ identification of the terpinolene and α-phellandrene-rich chemotype instead of conducting hydrodistillation. These results offer interesting perspectives for the development of innovative natural ingredients for the topical route, ingredients obtained in an eco-responsible and non-destructive way.

Tragia L. Genus: Ethnopharmacological Use, Phytochemical Composition and Biological Activity

Tragia L. is a genus of plants belonging to the Euphorbiaceae family with worldwide intertropical distribution, composed of more than 150 species. In this literature review, 26 species of the genus used as medicinal plants were found, mainly in East Africa and the Indian subcontinent, with a variety of uses among which antibacterial, anti-inflammatory, anticancer and reproductive health are most common. Research has been done on a few of the species, mostly those of the Old World, with emphasis on four of them: Tragia involucrata Linn., Tragia spathulata Benth., Tragia benthamii Baker and Tragia plukenetii Radcl.-Sm., confirming several ethnomedicinal claims. Moreover, a variety of active phytochemicals have been isolated, mainly ethers, hydrocarbons, flavonoids and sterols. There is ample field for the evaluation of the activity of Tragia extracts and essential oils and the identification of their active compounds, particularly of the New World species, for which there is still very little research.

Zanthoxylum Species: A Review of Traditional Uses, Phytochemistry and Pharmacology in Relation to Cancer, Infectious Diseases and Sickle Cell Anemia

The health benefits and toxicity of plant products are largely dependent on their secondary metabolite contents. These compounds are biosynthesized by plants as protection mechanisms against environmental factors and infectious agents. This review discusses the traditional uses, phytochemical constituents and health benefits of plant species in genus Zanthoxylum with a focus on cancer, microbial and parasitic infections, and sickle cell disease as reported in articles published from 1970 to 2021 in peer-reviewed journals and indexed in major scientific databases. Generally, Z. species are widely distributed in Asia, America and Africa, where they are used as food and for disease treatment. Several compounds belonging to alkaloids, flavonoids, terpenoids, and lignans, among others have been isolated from Z. species. This review discusses the biological activities reported for the plant species and their phytochemicals, including anticancer, antibacterial, antifungal, antiviral, anti-trypanosomal, antimalarial and anti-sickling properties. The safety profiles and suggestions for conservation of the Z. species were also discussed. Taken together, this review demonstrates that Z. species are rich in a wide range of bioactive phytochemicals with multiple health benefits, but more research is needed towards their practical application in the development of functional foods, nutraceuticals and lead compounds for new drugs.

Flavanols and triterpenoids from Myrianthus arboreus ameliorate hyperglycaemia in streptozotocin-induced diabetic rats possibly via glucose uptake enhancement and α-amylase inhibition

Myrianthus arboreus is use traditionally as an antidiabetic agent in Ghana. We reported the in vivo antidiabetic activity of its 70 % ethanol stem bark extract (MAB) which we found to be strongly concentrated in its EtOAc fraction using glucose uptake and enzyme inhibitory assays. The present study sought to investigate the in vivo hypoglycaemic and anti-hyperlipidaemic activity of this ethyl acetate fraction of MAB (MAB-EtOAc, 50 and 100 mg/kg) in streptozotocin (STZ)-induced diabetic rats for 21 days, isolate and evaluate the bioactive constituents responsible for the antidiabetic activity. In silico pharmacokinetic and toxicity properties of the most active compound was also determined. MAB-EtOAc significantly (p < 0.001) reduced the blood glucose levels while normalizing considerably the altered serum lipid parameters of the diabetic rats which was comparable to glibenclamide (5 mg/kg). Chemical investigation of MAB-EtOAc led to the isolation of seven known compounds including three flavanols which are reported for the first time in the plant: epicatechin (1), epigallocatechin (2), dulcisflavan (3), euscaphic acid (4), tormentic acid (5), sitosterol-3-O-β-d-glucopyranoside (6) and arjunolic acid (7). The compounds markedly inhibited the action of α-amylase and, except for 4 and 6, which stimulated considerably glucose uptake in C2C12 cells. Compounds 2, 3, 5, 6 and 7 which were further evaluated in STZ-induced diabetic rats demonstrated hypoglycaemic and anti-hyperlipidaemic activities which, however, were not comparable with MAB-EtOAc. Compound 3, the most active compound was predicted to be non-toxic, non-mutagenic, has reasonable oral bioavailability and a decent substrate for further drug development. The findings of this study show that the isolated compounds may contribute to the antidiabetic activity of M. arboreus and could serve as marker compounds for the quality control of herbal medicines that would be made from the plant.

Plukenetia huayllabambana Fruits: Analysis of Bioactive Compounds, Antibacterial Activity and Relative Action Mechanisms

Plukenetia huayllabambana is an edible plant traditionally used to cure wounds and various infections. The present work assessed, for the first time, the antibacterial efficacy of solvent fractions from P. huayllabambana fruits. The crude methanol extract was obtained applying ultrasound-assisted extraction, followed by partitioning through successive depletion among solvents of increasing polarity to yield fractions (n-hexane, dichloromethane, ethyl acetate, and n-butanol). The minimal inhibitory concentration (MIC) was determined following antibacterial testing, using the broth microdilution technique against a panel of drug-resistant Gram-negative and Gram-positive bacteria. Possible modes of action of the most active fraction were also investigated. Gas chromatography-mass spectrometry (GC-MS) was used to identify phytocompounds that may account for the recorded activities. Methanol, n-hexane (PH-n-Hex), and ethyl acetate extracts inhibited 100% of studied bacteria, with the recorded MIC ranging from 0.125-1 mg/mL. PH-n-Hex appeared as the most active partition, exerting a bacteriostatic effect. PH-n-Hex probably acts by interfering with bacterial biofilm formation, proton pumps, and bacterial cell membrane integrity. The GC-MS analysis of PH-n-Hex led to the identification of 11 potentially bioactive components, including fatty acids, phytosterol, and diterpene alcohol as major ones. P. huayllabambana can be considered as a plant of pharmacological value-a source of potent anti-infective drug entities.

In Vitro Antibacterial and Antiproliferative Potential of Echinops lanceolatus Mattf. (Asteraceae) and Identification of Potential Bioactive Compounds

Many species belonging to the genus Echinops are widely used in traditional medicine to treat infectious diseases and cancers. The present study aimed to evaluate the antibacterial and antiproliferative properties of Echinops lanceolatus Mattf. (Asteraceae). The activity of the methanolic extract and subsequent partition fractions was investigated against drug-resistant bacteria (Gram-negative and Gram-positive) and human tumor cell lines using broth microdilution and sulforhodamine B (SRB) assay, respectively. Our findings revealed weak to moderate antibacterial activities of tested extracts, with the recorded minimal inhibitory concentrations ranging from 256 to 1024 µg/mL. The ethyl acetate fraction (EL-EA) was found to be the most effective. Likewise, that fraction displayed strong antiproliferative potential with recorded IC50 of 8.27 µg/mL and 28.27 µg/mL on A549 and HeLa cells, respectively. An analysis based on the ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) of the EL-EA fraction allowed the identification of 32 compounds, of which quinic acid and derivatives, cinnamic acid derivatives, dihydrokaempferol, naringenin-7-O-glucoside, apigenin-7-O-d-glucoside, naringin, apigenin, rhoifolin, coniferyl aldehyde, and secoisolariciresinol are well-known compounds of biological importance. This study is first to report on the biological activity and phytochemical profile of E. lanceolatus. We provide a baseline to consider E. lanceolatus as a valuable source of anti-infective and antiproliferative agents.

Further isolation and identification of anti-diabetic principles from root bark of Myrianthus arboreus P. Beauv.: The ethyl acetate fraction contains bioactive phenolic compounds that improve liver cell glucose homeostasis

ETHNOPHARMACOLOGICAL RELEVANCE

We recently reported that ethanol extract of Myrianthus arboreus P. Beauv. root bark demonstrated antidiabetic activity by modulating hepatocyte glucose homeostasis. This activity was associated significantly to the ethyl acetate (EAc) fraction. The current study sought to identify the active compounds responsible of the antidiabetic effect of M. arboreus in the EAc fraction using bioassay-directed sub-fractionation.

MATERIALS AND METHODS

EAc fraction was sub-fractionated using Flash chromatography. Preparative HPLC was used to isolate the pure compounds. The structures of the isolated compounds were confirmed by analysis of NMR spectroscopic and mass spectrometric data. Hepatic (H4IIE, HepG2) cells were treated with maximum non-toxic concentrations of ethanol extract, its EAc fraction and isolated compounds thereof. Glucose-6-phosphatase (G6Pase) activity was measured using the glucose oxidase method. To measure glycogen synthase (GS) activity, radioactive assays were used. Phosphorylation of AMP-activated protein kinase (AMPK) and Glycogen Synthase Kinase-3 (GSK-3) were probed by Western blot.

RESULTS

Six sub-fractions were obtained, and the antidiabetic activity was found in two sub-fractions (SFE1 and SFE2). For the first time, two known C-glycosylflavone regio-isomers, isoorientin (1) and orientin (2) were detected and isolated from M. arboreus plant, especially from SFE2 as well as protocatechuic acid, 3,4-dihydroxybenzaldehyde (4), and chlorogenic acid isolated from SFE1. The compounds 1, 2, 4 were determined to decrease the activity of G6Pase by increasing AMPK phosphorylation and to stimulate GS through GSK-3 phosphorylation. Isoorientin which is one of the main compounds of EAc fraction, expressed the strongest effect in all bioassays, similar to that of the EAc fraction. A significant and linear correlation was found between the phosphorylation of AMPK and the activity of G6Pase modulated by all samples (R² = 0.54; p < 0.05). Similar to G6Pase assay, a correlation was determined between the capacity of M. arboreus extracts/fractions/compounds to stimulate GS activity and to phosphorylate GSK-3 (R² = 0.57, p < 0.01).

CONCLUSION

Results demonstrate that 1, 2, 4 are responsible, at least in part, for the antidiabetic activity of M. arboreus. These compounds can be used to ensure the quality and efficacy of M. arboreus antidiabetic preparations and standardize such preparations.

Bioactive Pentacyclic Triterpenes from the Root Bark Extract of Myrianthus arboreus, a Species Used Traditionally to Treat Type-2 Diabetes

Four new Δ¹² ursene-type pentacyclic triterpenes containing the trans-feruloyl moiety (1-4), along with ursolic acid (5), were isolated from a Myrianthus arboreus root bark ethanol extract, after bioassay-guided subfractionation of its hexane fraction. The structures of 1-4 were established on the basis of the results of standard spectroscopic analytical methods (IR, HRESIMS, GC-MS, 1D and 2D NMR). The compounds 3β- O- trans-feruloyl-2α,19α-dihydroxyurs-12-en-28-oic acid (1), 2α-acetoxy-3β- O- trans-feruloyl-19α-hydroxyurs-12-en-28-oic acid (3), and 5 were determined to decrease the activity of hepatocellular glucose-6-phosphatase (G6Pase) and to activate glycogen synthase (GS). Their action on G6Pase activity implicated both Akt and AMPK activation. In addition, these compounds were determined to stimulate GS via the phosphorylation of glycogen synthase kinase-3. Compound 3 showed the most potent effect in modulating glucose homeostasis in liver cells. This is the first comprehensive report on novel phytochemical components of the root bark extract of M. arboreus based on the isolation of the principles responsible for its antidiabetic effects.

Myrianthus arboreus P. Beauv (Cecropiaceae) Extracts Accelerates Sexual Maturation, and Increases Fertility Index and Gestational Rate in Female Wistar Rats

Background: Despite the wide use of leaves of Myrianthus arboreus (Cecropiaceae) in several African countries including Cameroon as food and against amenorrhea and female infertility, it has never been tested for this purpose. Methods: Using immature female Wistar rats, the impact of M. arboreus on the sexual maturation parameters (vaginal opening, ovarian relative weight and follicle maturation, gonadotropins and ovarian hormones serum levels) and fertility index has been evaluated through a 30-day oral administration of aqueous and methanol extracts of leaves at the doses of 20, 110 and 200 g/kg/day. Results: Aqueous extract increased the ovarian relative weight (p < 0.001), progesterone (p < 0.001) and gonadotropins (p < 0.001) serum levels, and induced the maturation of ovarian follicles. The methanol extract additionally induced an early vaginal opening (p < 0.001), uterine growth (p < 0.01) and increased estradiol (p < 0.001) serum levels. The fertility index generally increased following treatments, while the gestation rate remained almost unaffected except at the highest tested dose of M. arboreus extracts where lowest values were observed. Conclusion: Globally, M. arboreus induced an early puberty onset and an increased fertility rate validating at least in part its traditional use for female infertility.

Anti-inflammatory effects and anti-oxidant capacity of Myrathius arboreus (Cecropiaceae) in experimental models

BACKGROUND

Inflammation is involved in various diseases; search for safe treatments is warranted. Anti-inflammatory effects of ethanol extract of Myrathius arboreus (EEMa) were studied in carrageenan-induced model, formaldehyde sub-acute-induced model, and in 48 h lipopolysaccharide-induced air pouch model of inflammation. EEMa membrane-stabilizing activities and anti-oxidant capacity were determined in vitro.

METHODS

In the carrageenan model EEMa (125, 250, or 500 mg/kg), indomethacin (5 mg/kg), or vehicle 3 mL/kg was administered orally in rats (n=5). After 1 h, 0.1 mL of 1% carrageenan was injected into the right hind paw of rats. Change in edema sizes was measured for 3 h with plethysmometer. One-tenth milliliter (0.1 mL) of 2.5% formaldehyde was injected into the rat paw on the first day and the third day to induce sub-acute inflammation; changes in the edema sizes were determined, and percentages of inhibitions were calculated. Anti-inflammatory effects of EEMa were further examined in lipopolysaccharide (LPS)-induced air-pouch based on leukocytes count, volume of exudates, levels of malondialdehyde, glutathione, superoxide dismutase, nitric oxides, and tumor necrosis factor released into the inflammatory fluids. EEMa-free radicals scavenging activities were studied in DPPH and reducing power tests. Membrane-stabilizing activities of EEMa were evaluated in the red blood cell lysis induced by thermal and hypotonic solution.

RESULTS

EEMa (250, 500 mg/kg) produced significant (p<0.001; p<0.05) inhibition of inflammation when compared with vehicle. Also, EEMa (250, 500, or 1000 μg/mL) significantly stabilized membrane and produced free radical scavenging activities.

CONCLUSIONS

M. arboreus possesses anti-inflammatory and the anti-oxidant properties that might benefit translational medicine.

Safety evaluation (acute and sub-acute studies) of the aqueous extract of the leaves of Myrianthus arboreus P. Beauv. (Cecropiaceae) in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Myrianthus arboreus P. Beauv (Cecropiaceae) is a medicinal plant distributed in forests and damp places of tropical Africa. Its leaves are widely used as food and/or for the treatment of various ailments including dysmenorrhoea, female infertility, tumors and diarrhea. However, to the best of our knowledge, no safety assessment of this plant has been reported yet.

AIM OF STUDY

The present study aimed at evaluating the safety of the aqueous extract of leaves of Myrianthus arboreus (MAA) in Wistar rats through an acute and sub-acute oral administration.

MATERIAL AND METHODS

In acute oral toxicity, the test was performed according to the Organization for Economic Cooperation and Development (OECD) guidelines Nr. 423 (acute toxicity class method, ATC) with slight modifications. Female Wistar rats were orally treated with the aqueous extract of M. arboreus at the doses of 2000 and 5000mg/kg. In sub-acute toxicity study, using the OECD guidelines Nr. 407, the extract was administered by gavage at the doses of 20, 110 and 200mg/kg/day for 28 consecutive days.

RESULTS

A single oral administration of 2000 or 5000mg/kg of the extract induced neither mortality nor exterior signs of toxicity indicating a LD₅₀ >5000mg/kg. In sub-acute study, the extract decreased triglycerides, total cholesterol/high density lipoproteins ratio and atherogenic index of plasma in both sexes at all tested doses. Alanine transaminase decreased in both sexes at 200mg/kg and serum creatinine levels decreased at all tested doses in females. Moreover, significant increases in ovarian and uterine wet weights, red blood cell count, hematocrit, mean corpuscular hemoglobin and hemoglobin were observed at 200mg/kg in females. In males, this extract decreased white blood cell count, lymphocytes and relative weight of seminal vesicles and ventral prostate at 200mg/kg.

CONCLUSION

The aqueous extract of Myrianthus arboreus leaves was non-toxic in acute administration and exhibited a relatively low toxicity potential on accessory sex organs in both sexes, and leukocytes in males following the repeated 28-days oral administration of the dose 200mg/kg.