Papers by Frederic Nico Njayou
Revista Brasileira de Farmacognosia, Jun 15, 2024
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African Journal of Traditional, Complementary and Alternative Medicines, Oct 20, 2008
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Czech Mycology, 2020
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International Journal of Phytomedicine, Jan 17, 2021
Alzheimer’s disease (AD) belongs to the class of neurodegenerative disorder and is biochemically ... more Alzheimer’s disease (AD) belongs to the class of neurodegenerative disorder and is biochemically characterized by amyloid-β (Aβ) plaques deposition, accumulation of neurofibrillary tangles (NFTs) accumulation and ultimately neuronal loss. Even though, the progress made in developing efficient AD therapy, there is no effective drug capable to stop and/or slow down AD progression. In the current article, we investigated the neuroprotective effect of Khaya grandifololia crude extract and fraction 2 against Aβ 42 -induced cytotoxicity and hyperphosphorylation of tau protein in differentiated neuronal cells (IMR32). Reactive oxygen species production, apoptosis and mitochondrial dynamics and function, synaptic protein, and tau phosphorylation were evaluated using fluorescence microscopy and immunoblotting. Cell viability was assessed using the MTT assay. Findings revealed that exposure of differentiated IMR32 cells to Aβ 42 alone induced the impairment of mitochondrial dynamics, decrease synaptic protein expression and increase hyperphosphorylation of tau protein (phospho tau181). In contrast, the presence of crude extract and KGf2 significantly inhibited the cleavage of Caspase-3 activation. In addition, the levels of synaptic proteins (Symptosomal associated protein 25 and Synaptosin) and superoxide dismutase were restored upon treatment with crude extract and fraction 2. Hyperphosphorylation of tau protein (Thr181) and ERK (Thr202/Tyr205) activities were also significantly reduced after treatment with crude extract and fraction 2. Our findings suggest that KG extract is a potential source for candidate drug against AD and may contribute to the development of efficient therapeutic strategy against AD.
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World Journal of Advanced Research and Reviews
Background: Wild edible fruits are good source of phenolic compounds such as anthocyanins. Those ... more Background: Wild edible fruits are good source of phenolic compounds such as anthocyanins. Those compounds are known for their anti-inflammatory potential. They interact with many mediators of the physiopathological pathway such as NF-kB which is at a central position in the inflammatory response in macrophages. This study aimed to determine the anti-inflammatory and antioxidant potential of ten wild edible fruits aqueous extracts. Methods: The antioxidant potential was evaluate through the DPPH, ABTS and OH radical scavenging activity; the ferric reducing agent power and the total antioxidant capacity assessment. Also, the total phenolic and flavonoids, anthocyanins compounds and vitamin C content were assayed. For the anti-inflammatory activity, a primary macrophage culture was used. Inflammatory mediators such as nitric oxide (NO), alkaline phosphatase, NADPH oxidase and 5-lipoxigenase activity was assayed. Results: Alchornea cordifolia and Pentaclethra macrophylla extracts showe...
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Amoebiasis, classified as the third intestinal parasitic infection, represents a public health pr... more Amoebiasis, classified as the third intestinal parasitic infection, represents a public health problem in low-income countries where hygiene and sanitation conditions are poor. With the resurgence of resistant pathogenic strains as well as ancestral considerations in developing countries such as Cameroon, many people rely on medicinal plants to treat a plethora of diseases.
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Codiaeum variegatum has been widely investigated for its biological proprieties ranging from the ... more Codiaeum variegatum has been widely investigated for its biological proprieties ranging from the antiamoebic potential to the phytochemical analysis. The aim of the present study was to evaluate the anti-inflammatory potential of C. variegatum leaf extracts and fractions. A primary macrophage culture activated by Saccharomyces cereviseae (SC) was used to evaluate cell cytotoxicity and anti-inflammatory potential of the plant extracts and fractions. Macrophages were treated with different concentrations (0.1; 1; 10 and 100 μg/mL) of the extracts/fractions for the inhibition of 5-lipoxygenase activity, nitric oxide (NO) and Tumor Necrosis Factor Alpha (TNF-α) production. No significant difference was observed on cell viability in the presence of extracts and fractions at tested concentration during the incubation period. Extracts and fractions of C. variegatum inhibited the 5-lipoxygenase activity, NO and TNF-α production by viable primary mouse macrophages in a concentrationdependent manner. The fractionation process increased anti-inflammatory activity. Among fractions, HEF2, HEF3, HEF5, EEF1, EEF3 and EEF5 exhibited the best anti-inflammatory potential. C. variegatum extracts and fractions exhibited a greater anti-inflammatory potential throughout the inhibition of pro-inflammatory mediators such as NO, 5-Lox and TNF-α.
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Background: Sida rhombifolia (L) is a medicinal plant from tropical regions belonging to the Malv... more Background: Sida rhombifolia (L) is a medicinal plant from tropical regions belonging to the Malvaceae family and the plantea kingdom. It is known for its multiple pharmacological properties. The aim of this work was to evaluate the anti-amoebic, and anti-inflammatory potential of Sida rhombifolia aqueous and ethanolic leaf and stem extracts harvested in two localities of Cameroon (Yaoundé and Massangam in the Centre and West regions, respectively). Methods: The anti-amoebic activity was evaluated on a polyxenic culture of Entamoeba histolytica. A primary macrophage culture activated by Saccharomyces cereviseae (SC) was used to evaluate anti-inflammatory potential of the plant extracts. Macrophages were treated with different concentrations (1; 10; 100 and 500 μg/mL) of the extracts for the inhibition of nitric oxide (NO) production and 5-lipoxygenase activity. Methods: The anti-amoebic activity was evaluated on a polyxenic culture of Entamoeba histolytica. A primary macrophage culture activated by Saccharomyces cereviseae (SC) was used to evaluate the anti-inflammatory potential of the plant extracts. Macrophages were treated with different concentrations (1; 10; 100 and 500 μg/mL) of the extracts for the inhibition of nitric oxide (NO) production and 5-lipoxygenase activity. Results: No significant difference was found between the anti-amoebic activity of the ethanolic extract of Yaoundé (Centre region, IC50 = 7.71 μg/mL) and that of ethanolic leaf extract from Massagam (West region IC50 = 7.77 μg/mL) after 72 hours. Among the extracts, ethanolic leaf extracts exhibited the highest anti-amoebic activity after 72 hours of treatment. Metronidazole showed better activity (IC50 = 5.96 µg/mL) in the same periods of time. Phenolic compounds and flavonoid contents were higher in Yaoundé (Centre region) ethanolic leaf extract, proving that these extracts can prevent certain damages linked to a state of oxidative stress. The ethanolic extracts of the leaves significantly inhibited NO production and 5-lipoxygenase activity in macrophages (IC50 of 3.85 µg/mL; 3.99 µg/mL and 36.64 µg/mL; 73.22 µg/mL respectively). Conclusion: This preliminary study shows that the ethanolic extract of S. rhombifolia possesses better anti-amoebic properties and can act at the level of the intestinal mucosa in order to fight against the damage linked to the dysfunction of the inflammatory cells.
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Background and objectives: Codiaeum variegatum (C. variegatum), which is commonly known as garden... more Background and objectives: Codiaeum variegatum (C. variegatum), which is commonly known as garden croton, is a medicinal plant used for the treatment of amoebiasis in Cameroon and some Asian countries. The present study aims to evaluate the antioxidant and anti-inflammatory activities of the stem crude extracts of C. variegatum. Methods: Aqueous, hydroethanolic 70/30 (v/v) and ethanolic extracts were tested for antioxidant activity using DPPH radical scavenging, ferric iron-reducing antioxidant power (FRAP), and lipid peroxidation inhibitory assays. The anti-inflammatory activity was determined based on the inhibition of nitric oxide production on isolated mouse macrophages activated by Saccharomyces cerevisiae. Furthermore, the inhibitory effect of these extracts on 5-lipoxygenase activity and bovine serum albumin (BSA) denaturation was determined, and the activation of two lysosomal enzymes involved in phagocytosis was performed. The phytochemical screening of the plant extracts was performed using standard methods. Results: The results revealed that the ethanolic extract (EE) exhibited the highest antioxidant activity, in terms of DPPH-free radical scavenging activity, FRAP, and its potential to inhibit lipid peroxidation (IC 50 = 77.04 µg extract/mol of DPPH; EC 50 = 543.6 µg/mL and IC 50 = 21.52 µg/mL, respectively). However, this activity remained significantly lower than that of ascorbic acid (p < 0,05). Furthermore, the hydroethanolic extract (HE) had the highest anti-inflammatory activity on isolated mouse macrophages, in terms of inhibitory activity on NO production, BSA denaturation, and 5-lipoxygenase activity (IC 50 = 8.80 µg/mL, IC 50 = 205.9 µg/mL, IC 50 = 0.08 µg/mL, respectively). However, there was no significant difference in the inhibitory activity of baicalin. Moreover, the activity of acid phosphatase and alkaline phosphatase increased in the presence of the HE (EC 50 = 10.03 µg/mL and EC 50 = 0.274 µg/mL, respectively). The phytochemical analysis of these extracts indicates the presence of phenolic compounds, and these may be responsible for the observed activities. Conclusions: Overall, these results demonstrate that the hydroethanolic and ethanolic stem extracts of C. variegatum have good antioxidant and anti-inflammatory potential.
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Asian Journal of Research in Medical and Pharmaceutical Sciences
Aims: The present work aimed to evaluate the anti-amoebic, antibacterial, and anti-inflammatory p... more Aims: The present work aimed to evaluate the anti-amoebic, antibacterial, and anti-inflammatory potential of three natural polyketides from Phomopsis sp. CAM212. Study Design: Clinical isolates of E.histolytica, E.coli ATCC25922 strain, primary peritoneal mouse macrophages and three polyketides were used. Places and Duration of Study: Laboratory of Pharmacology and Toxicology, Laboratory of Medical Microbiology, Faculty of Science, University of Yaounde 1 between May and December 2022. Methodology: During this work, we evaluated the ability of three natural polyketides from Phomopsis sp to inhibit the growth of germs responsible for amoebic and bacillary dysentery. First, the anti-amoebic activity was carried out on clinical isolates of E. histolytica in polyxenic culture. Subsequently, we evaluated the antibacterial potential on a strain of E. coli ATCC25922. Finally, the anti-inflammatory potentials were evaluated on a primary culture of SC activated macrophages through inhibition...
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Journal of Pharmacy and Pharmacology 6 (2018) 801-816, 2018
This study reports on the dietary exposure of people in Yaoundé, Cameroon to heavy metals: lead (... more This study reports on the dietary exposure of people in Yaoundé, Cameroon to heavy metals: lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu) and zinc (Zn). One hundred and fifty table-ready food, water and soft drink samples were collected from households and street restaurants in Yaoundé and analyzed for heavy metals contents using atomic absorption spectrophotometer. Lead (93%, range 0.019-1.77 ppm), Cd (70%, range 0.01-4.68 ppm), Hg (81%, range 0.03-10.56 ppm), Cu (90%, range 0.004-40.32 ppm) and Zn (87%, range 0.014-2,447.04 ppm) were detected in studied samples. Maximum level of each metal exceeded its corresponding European Commissions legislative limits. Samples from street restaurants were most tainted with heavy metals. The highest average daily intakes (ADIs) of Pb (0.96 mg/day) and Hg (1.84 mg/day) were through tap water, while Cd (1.15 mg/day), Cu (5.42 mg/day) and Zn (601.6 mg/day) were through rice/peanut sauce mixed food. The ADI for Cd and Hg was each higher than it...
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African Journal of Biochemistry Research
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BMC complementary and alternative medicine, Jan 7, 2016
Khaya grandifoliola (Meliaceae) and Entada africana (Fabaceae) are traditionally used in Bamun (a... more Khaya grandifoliola (Meliaceae) and Entada africana (Fabaceae) are traditionally used in Bamun (a western tribe of Cameroon) traditional medicine for the treatment of liver related diseases. In this study, the synergistic hepatoprotective effect of respective active fractions of the plants were investigated against paracetamol-induced toxicity in primary cultures of rat hepatocytes. Paracetamol conferred hepatocyte toxicity, as determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay, alanine aminotransferase (ALT), superoxide dismutase (SOD), catalase (CAT) activities, malondialdehyde (MDA) and glutathione (GSH) content assays. The crude extracts were fractionated by flash chromatography and fractions were tested for hepato-(protective and curative) activities. The most active fractions of both plants were tested individually, and in combination based on their respective half effective concentration (EC50). The methylene chloride/methanol fractions of K. g...
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International Journal of Biological Chemistry
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Journal of the Cameroon …, 2005
... 'Laboratory of Biochemical Toxicology and Nutrition, University of Yaounde l, 2Departmen... more ... 'Laboratory of Biochemical Toxicology and Nutrition, University of Yaounde l, 2Department of Biochemistry, U niver-slty of ... Williams, R. (1995) : Protection against galactosamine and Tert-buthylhydroperoxide in-duced hepatocyte damage by M el oz/aria maderaspanara extract. ...
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Journal of Complementary Medicine Research
Background/Aim: The decoction of Codiaeum variegatum leaves is used by Cameroonian local populati... more Background/Aim: The decoction of Codiaeum variegatum leaves is used by Cameroonian local population in the treatment of amoebic dysentery. The present study was carried out to investigate the safety of the aqueous extract of Codiaeum variegatum leaves on mice and rats of both sexes. Methods: For the acute toxicity study, seven groups of 8 Wistar mice (4 males and 4 females) received orally once distilled water (10 mL.Kg-1) and the aqueous extract in a single dose of 2, 4, 8, 12, 16, and 24 g.Kg-1. These mice were observed for mortality after 48 hours and thereafter for clinical signs daily for 14 days. In the subchronic toxicity evaluation, four groups of 12 Wistar rats (6 males and 6 females) received distilled water (10 mL.Kg-1) and the aqueous extract at doses of 50, 100, and 200 mg.Kg-1 by oral gavage for 28 consecutive days. The body weight was evaluated every 2 days for each animal and after sacrifice, the relative weight of vital organs was determined. Blood serum was used for the analysis of biochemical markers of renal and hepatic toxicity. Results: The administration of the aqueous extract in both acute and subchronic toxicity evaluation did not cause neither significant visible signs of toxicity nor mortality and no significant changes were observed on body weight, relative organ weight and biochemical parameters in treated groups compared to the control groups respectively. Conclusion: These results demonstrated that the aqueous extract of Codiaeum variegatum leaves is non-toxic and may be safely used for its therapeutic application.
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Journal of Complementary Medicine Research
Background/Aim: The decoction of Codiaeum variegatum leaves is used by Cameroonian local populati... more Background/Aim: The decoction of Codiaeum variegatum leaves is used by Cameroonian local population in the treatment of amoebic dysentery. The present study was carried out to investigate the safety of the aqueous extract of Codiaeum variegatum leaves on mice and rats of both sexes. Methods: For the acute toxicity study, seven groups of 8 Wistar mice (4 males and 4 females) received orally once distilled water (10 mL.Kg-1) and the aqueous extract in a single dose of 2, 4, 8, 12, 16, and 24 g.Kg-1. These mice were observed for mortality after 48 hours and thereafter for clinical signs daily for 14 days. In the subchronic toxicity evaluation, four groups of 12 Wistar rats (6 males and 6 females) received distilled water (10 mL.Kg-1) and the aqueous extract at doses of 50, 100, and 200 mg.Kg-1 by oral gavage for 28 consecutive days. The body weight was evaluated every 2 days for each animal and after sacrifice, the relative weight of vital organs was determined. Blood serum was used for the analysis of biochemical markers of renal and hepatic toxicity. Results: The administration of the aqueous extract in both acute and subchronic toxicity evaluation did not cause neither significant visible signs of toxicity nor mortality and no significant changes were observed on body weight, relative organ weight and biochemical parameters in treated groups compared to the control groups respectively. Conclusion: These results demonstrated that the aqueous extract of Codiaeum variegatum leaves is non-toxic and may be safely used for its therapeutic application.
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ObjectivesAlthough global epidemiology of Helicobacter pylori (HP) infection is well characterize... more ObjectivesAlthough global epidemiology of Helicobacter pylori (HP) infection is well characterized, country-specific figure is more accurate for context-specific tailored interventions. The aim was to determine the prevalence, factors associated with infection, antibiotic resistance profile, and genotypes of HP in Cameroon.DesignA systematic review with meta-analysis.ParticipantsPeople living in Cameroon regardless of their clinical profile.Data sources and synthesisObservational studies published in PubMed, EMBASE, African Index Medicus, African Journals Online, and Health Sciences and Diseases up to October 12th, 2020. Study selection, data extraction, and methodological quality assessment were done by two independent authors. Random-effect meta-analysis served to pool prevalence data.ResultsFifteen studies were included. None investigated the genotypes of HP. Among symptomatic patients, the most common used test, urea breath test on gastric biopsy, yielded a prevalence 57.8% (95%...
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Antibiotics
The medicinal plant Spathodea campanulata P. Beauv. (Bignoniaceae) has been traditionally applied... more The medicinal plant Spathodea campanulata P. Beauv. (Bignoniaceae) has been traditionally applied for the prevention and treatment of diseases of the kidney and urinary system, the skin, the gastrointestinal tract, and inflammation in general. The present work shows for the first time how chemical components from this plant inhibit Helicobacter pylori growth by urease inhibition and modulation of virulence factors. The crude extract and the main fractions of S. campanulata bark were tested on H. pylori isolated strains and the active ones were further fractionated. Fractions and sub-fractions of the plant crude extract were characterized by ultra-high-performance liquid chromatographic tandem high resolution-mass spectrometry detection (UHPLC-HRMS). Several phenolics and triterpenoids were identified. Among the sub-fractions obtained, SB2 showed the capacity to inhibit H. pylori urease in a heterologous bacterial model. One additional sub-fraction (SE3) was able to simultaneously mo...
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Frontiers in Pharmacology
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Papers by Frederic Nico Njayou