Biofilm Formation and Phospholipase and Proteinase Production in Cryptococcus neoformans Clinical Isolates and Susceptibility towards Some Bioactive Natural Products.

Background: Cryptococcosis is one of the most common fungal infections in immunocompromised patients, which is caused by Cryptococcus neoformans. However, relatively little is known about the virulence factors of C. neoformans and the incidence of antifungal drug resistance in C. neoformans is rapidly increasing. This study was undertaken to investigate the virulence factors in C. neoformans, thymol, curcumin, piperine, gallic acid, eugenol, and plumbagin for their potential antimicrobial activity against C. neoformans. Methods: The production of phospholipase and proteinase was detected using standard methods. Biofilm formation was determined using the microtiter plate method. The broth microdilution method was used to determine the antifungal activity. The antibiofilm activity was assessed using the safranin staining method. Results: All isolates of C. neoformans produced biofilms with optical density values ranging from 0.16 to 0.89. A majority of C. neoformans isolates that were tested exhibited strong phospholipase (7/8) and proteinase (5/8) production. Plumbagin (with minimum inhibitory concentration values ranging from 4 to 16 µg/mL) showed the highest antifungal activity followed by thymol (with minimum biofilm inhibitory concentration values ranging from 8 to 64 µg/mL). In addition, plumbagin showed the highest antibiofilm activity with minimum biofilm inhibitory concentration and minimum biofilm eradication concentration values ranging from 4 to 16 µg/mL and 32 to 256 µg/mL, respectively. Conclusion: Plumbagin, compared to other natural products studied, was the most efficient in terms of antifungal and antibiofilm activities. Hence, plumbagin could be used in combination with antifungals for the development of new anticryptococcal drugs.

Antibiofilm Activity and Synergistic Effects of Thymol-Loaded Poly (Lactic-Co-Glycolic Acid) Nanoparticles with Amikacin against Four Salmonella enterica Serovars.

Background: Salmonella species are frequently linked to biofilm-associated infections. Biofilm formation intensively reduces the efficacy of antibiotics and the host immune system. Therefore, new therapeutic strategies are needed. Thymol, the main monoterpene phenol found in Thymus vulgaris, has been shown to possess potent antibiofilm activity. Our previous findings showed that thymol enhanced the antibiofilm activity of aminoglycosides against Salmonella enterica serovars. However, the clinical potential of thymol has not yet been realized due to its low aqueous solubility and high volatility. Nano-based drug delivery systems have emerged as a novel strategy to resolve these problems. This study aimed to investigate the antibiofilm activity of thymol-loaded poly (lactic-co-glycolic acid) nanoparticles (TH-NPs) and their synergism when used in combination with amikacin antibiotics. Methods: The antibacterial activity of TH-NPs was evaluated using the broth microdilution method. Biofilm formation and antibiofilm assays were performed by the miniaturized microtiter plate method. Interaction studies between TH-NPs and amikacin against biofilm were determined using the checkerboard method. Results: TH-NPs exhibited antibacterial activity against planktonic cells of S. enterica serovars that were more efficient (8 to 32 times) than free thymol alone. S. Typhimurium and S. Choleraesuis isolates were considered strong biofilm producers. The combination of TH-NPs with amikacin showed synergistic activity in the inhibition and eradication of S. enterica serovar biofilm. The minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC) of amikacin were reduced by 32 to 128-fold when used in combination with TH-NPs. Time-kill kinetic studies showed that the combination of TH-NPs with amikacin possesses bactericidal action. Conclusion: This study suggests that the combination of TH-NPs with amikacin can be an alternative to overcome biofilm-associatedSalmonella diseases and therefore should be further explored as a model to search for new antibiofilm drugs.

Relationship between active Helicobacter pylori infection and risk factors of cardiovascular diseases, a cross-sectional hospital-based study in a Sub-Saharan setting.

BACKGROUND: Chronic inflammation has been reported as one of the novel coronary heart disease (CHD) risk factors. Knowing that Helicobacter pylori (H. pylori) provokes a local inflammation, the relationship between H. pylori infection and cardiovascular disease (CVD) has received considerable attention. However, the attempt to demonstrate the association between H. pylori and specific cardiovascular disease risk factors is always a challenging issue due to the conflicting reports in the literatures. METHODS: We performed a cross-sectional study of 363 consecutive dyspeptic subjects in three reference health facilities in Cameroon from October 2020 to October 2021. Each participation gave a written consent and the study was approved by the local Ethical Committee. Check-up for cardiovascular disease (CVD) risk factors such as dyslipidemia-related parameters, obesity-related parameter, high blood pressure as well as H. pylori detection was done for each participant. Data was analyzed using SSPS statistical package. RESULTS: Helicobacter pylori infection was significantly associated with higher total cholesterol level (OR: 2.3324, p = 0.0002) and higher LDL cholesterol level (OR: 2.3096, p = 0.0006). The crude OR of H. pylori status on the prevalence of high body mass index (BMI) was 1.0813 (p = 0.7300) and the adjusted OR for confounding factors was 1.1785 (p = 0.5095). The strength of the association between H. pylori infection and blood pressure, shows an OR of 1.3807 (p = 0.2991), 1.0060 (p = 0.9855) and 1.4646 (p = 0.2694) for diastolic pressure, hypertension and high heart rate respectively, while that of systolic pressure was 0.8135 (p = 0.4952). H. pylori infection is associated with dyslipidemia in our milieu.

Multilocus sequence typing (MLST) analysis reveals many novel genotypes and a high level of genetic diversity in Candida tropicalis isolates from Italy and Africa.

BACKGROUND: Candida tropicalis is a human pathogenic yeast frequently isolated in Latin America and Asian-Pacific regions, although recent studies showed that it is also becoming increasingly widespread throughout several African and south-European countries. Nevertheless, relatively little is known about its global patterns of genetic variation as most of existing multilocus sequence typing (MLST) data come from Asia and there are no genotyped African isolates. OBJECTIVES: We report detailed genotyping data from a large set of C. tropicalis isolates recovered from different clinical sources in Italy, Egypt and Cameroon in order to expand the allele/genotype library of MLST database (https://pubmlst.org/ctropicalis), and to explore the genetic diversity in this species. METHODS: A total of 103 C. tropicalis isolates were genotyped using the MLST scheme developed for this species. All isolates were also tested for in vitro susceptibility to various antifungals to assess whether certain genotypes were associated with drug-resistance. RESULTS AND CONCLUSIONS: A total of 104 different alleles were detected across the MLST-loci investigated. The allelic diversity found at these loci resulted in 51 unique MLST genotypes of which 36 (70.6%) were novel. Global optimal eBURST analysis identified 18 clonal complexes (CCs) and confirm the existence of a specific Italian-cluster (CC36). Three CCs were also statistically associated with fluconazole resistance, which was elevated in Cameroon and Egypt. Our data show high genetic diversity in our isolates suggesting that the global population structure of C. tropicalis is still poorly understood. Moreover, its clinical impact in Italy, Egypt and Cameroon appears to be relevant and should be carefully considered.

Liposome-Encapsulated Bioactive Guttiferone E Exhibits Anti-Inflammatory Effect in Lipopolysaccharide-Stimulated MH-S Macrophages and Cytotoxicity against Human Cancer Cells.

Background: Guttiferone E is a naturally occurring polyisoprenylated benzophenone exhibiting a wide range of remarkable biological activities. But its therapeutic application is still limited due to its poor water solubility. This study is aimed at preparing guttiferone E-loaded liposomes and assessing their in vitro cytotoxicity and anti-inflammatory effect. Methods: Liposomes containing guttiferone E were prepared by the thin film hydration method, and the physicochemical characteristics were determined using dynamic light scattering, laser Doppler velocimetry, and atomic force microscopy. The cytotoxicity was assessed by the MTT assay. The fluorometric cyclooxygenase (COX) activity assay kit was used to assess the COX activity while the nitric oxide production was evaluated by the Griess reagent method. Results: The liposomes with a mean size of 183.33 ± 17.28 nm were obtained with an entrapment efficiency of 63.86%. Guttiferone E-loaded liposomes successfully decreased the viability of cancer cells. The overall IC50 values varied between 5.46 µg/mL and 22.25 µg/mL. Compared to the untreated control, guttiferone E-loaded liposomes significantly reduced the nitric oxide production and the activity of COX in a concentration-dependent manner. Conclusion: This study indicates that liposomes can be an alternative to overcome the water insolubility issue of the bioactive guttiferone E.

Antimicrobial and Cytotoxic Activities of Constituents from the Fruit of Albizia lebbeck L. Benth (Fabaceae).

Twenty-two compounds were isolated from the fruit of Albizia lebbeck including one unprecedented, rare amino acid-derived zwitterionic and one new flavone derivative. The isolation was performed on repeated column chromatography over silica gel and their structures were determined by 1D-, 2D-NMR and HR-ESI-MS spectra together with reported data in the literature. The chemophenetic significance is also discussed. Some isolated compounds were reported for the first time to be found in the species. Additionally, compound 2 showed antibacterial activity and compounds 1 and 2 revealed moderate cytotoxic activity against the Raw 264.7 cancer cell line with IC50 values of 37.19 µM and 29.36 µM, respectively. Furthermore, a proposed biosynthetic pathway of compound 1 is described.

Synergistic Antibiofilm Efficacy of Thymol and Piperine in Combination with Three Aminoglycoside Antibiotics against Klebsiella pneumoniae Biofilms.

BACKGROUND: Thymol and piperine are two naturally occurring bioactive compounds with several pharmacological activities. In this study, their antibiofilm potential either alone or in combination with three aminoglycoside antibiotics was evaluated against a biofilm of Klebsiella pneumoniae. METHODS: Determination of antimicrobial susceptibility was performed using the broth microdilution method. Biofilm formation was evaluated by the microtiter plate method. Antibiofilm activity was determined using 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium-bromide (MTT) assay. The combination studies were performed by the checkerboard microdilution method. RESULTS: The minimum biofilm inhibitory concentration (MBIC) of streptomycin was reduced by 16- to 64-fold when used in combination with thymol, while the MBIC of kanamycin was reduced by 4-fold when combined with piperine. The minimum biofilm eradication concentration (MBEC) values of streptomycin, amikacin, and kanamycin were, respectively, 16- to 128-fold, 4- to 128-fold, and 8- to 256-fold higher than the planktonic minimum inhibitory concentration (MIC). Thymol combined with streptomycin or kanamycin showed synergic effects against the preformed biofilm with 16- to 64-fold reduction in the minimum biofilm eradication concentration values of each antibiotic in combination. Piperine acted also synergically with kanamycin with an 8- to 16-fold reduction in the minimum biofilm eradication concentration values of kanamycin in combination. CONCLUSION: The association of thymol with antibiotics showed a strong synergistic effect both in the inhibition of biofilm formation and the destruction of the preformed biofilm of K. pneumoniae. This study suggests that a combination of thymol with streptomycin, amikacin, or kanamycin could be a promising alternative therapy to overcome the problem of K. pneumoniae biofilm-associated infections.

Inhibition of Nitric Oxide Production in LPS-Stimulated RAW 264.7 Macrophages and 15-LOX Activity by Anthraquinones from Pentas schimperi.

The anti-inflammatory activity of a coumarin and nine anthraquinone derivatives, 3-hydroxy-1-methoxy-2-methylanthraquinone (1), 2-hydroxymethyl anthraquinone (2), schimperiquinone B (3), cleomiscosin A (4), damnacanthal (5), 1,2-dihydroxy anthraquinone (6), damnacanthol (7), 3-hydroxy-2-hydroxymethyl anthraquinone (8), 1-hydroxy-2-methoxyanthraquinone (9), and 2-hydroxymethyl-3-O-prenylanthraquinone (10), isolated from the roots of Pentas schimperi were determined. The anti-15-lipoxygenase activity and nitric oxide production inhibition on lipopolysaccharide-activated macrophages RAW 264.7 cells were determined as indicators of anti-inflammatory activity. The Griess assay was used to measure nitric oxide production and the ferrous oxidation-xylenol orange assay was used to determine the 15-lipoxygenase inhibitory activity. All the compounds significantly decreased nitrite + nitrate accumulation in lipopolysaccharide-stimulated RAW 264.7 cells in a concentration-dependent manner with 85.67 % to 119.75 % inhibition of nitrite + nitrate production at 20 µg/mL. Most of the compounds had a moderate inhibitory effect on 15-lipoxygenase activity. Compounds 8 and 10 were the most potent inhibitor both in nitrite + nitrate production with respective IC50 values of 1.56 µM and 6.80 µM. Compounds 2, 7, and 8 had good anti-15-lipoxygenase activity with respective IC50 values of 13.80 µM, 14.80 µM, and 15.80 µM compared to quercetin, which was used as a standard lipoxygenase inhibitor (IC50 of 16.80 µM). Our study revealed 3-hydroxy-2-hydroxymethyl anthraquinone and damnacanthol as potent inhibitors of both 15-lipoxygenase activity and nitric oxide production. Further studies are needed in order to envisage its possible future use as a therapeutic alternative against inflammatory diseases.

The efficacy and safety of nine South African medicinal plants in controlling Bacillus anthracis Sterne vaccine strain.

BACKGROUND: Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive spore-forming bacterium. The presence of the bacteria and the toxins in the blood of infected hosts trigger a cascade of pathological events leading to death. Nine medicinal plants with good activities against other bacteria were selected to determine their in vitro antibacterial activity against Bacillus anthracis Sterne strain. The cytotoxicity of the extracts on Vero kidney cells was also determined. RESULTS: The minimum inhibitory concentration (MIC) values of the extracts against Bacillus anthracis Sterne strain ranged from 0.02 to 0.31 mg/ml. Excellent MIC values were observed for the following plant species: Maesa lanceolata (0.02 mg/ml), Bolusanthus speciosus, Hypericum roeperianum, Morus mesozygia (0.04 mg/ml) and Pittosporum viridiflorum (0.08 mg/ml). The total antibacterial activity of the extracts ranged from 92 to 5562 ml/g. Total activity presents the volume to which the extract from 1 g of plant material can be diluted and still inhibit microbial growth. Maesa lanceolata and Hypericum roeperianum had the highest total activity with values of 5562 and 2999 ml/g respectively. The extracts of Calpurnia aurea had the lowest total activity (92 ml/g). The cytotoxicity determined on Vero cells indicated that most of the extracts were relatively non-toxic compared to doxorubicin (LC50 8.3 ± 1.76 µg/ml), except for the extracts of Maesa lanceolata, Elaeodendron croceum and Calpurnia aurea with LC50 values at 2.38 ± 0.25, 5.20 ± 0.24 and 13 ± 2.26 µg/ml respectively. The selectivity index (SI) ranged from 0.02 to 1.66. Hypericum roeperianum had the best selectivity index, (SI = 1.66) and Elaeodendron croceum had lowest value (SI = 0.02). CONCLUSIONS: The crude acetone extracts of the selected plant species had promising antibacterial activity against Bacillus anthracis. Maesa lanceolata extracts could be useful as a disinfectant and Hypericum roeperianum could be useful to protect animals based on its high total activity and selectivity index. Further investigation of these plant extracts may lead to the development of new therapeutic agents to protect humans or animals against anthrax.

The anti-arthritic, anti-inflammatory, antioxidant activity and relationships with total phenolics and total flavonoids of nine South African plants used traditionally to treat arthritis.

BACKGROUND: Oxidative stress predisposes the human and animal body to diseases like cancer, diabetes, arthritis, rheumatoid arthritis, atherosclerosis and chronic inflammatory disorders. Hence, this study seeks to determine the antioxidant, anti-inflammatory and anti-arthritic activities of acetone leaf extracts of nine South African medicinal plants that have been used traditionally to treat arthritis and inflammation. METHODS: The anti-inflammatory activity of the extracts was determined by investigating inhibition of nitric oxide production in lipopolysaccharide activated RAW 264.7 macrophages as well as 15-lipoxygenase enzyme inhibition. An anti-protein denaturation assay was used to determine the anti-arthritic properties of the extracts. The antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) radical scavenging assays and ferric reducing antioxidant power (FRAP). The total phenolic and total flavonoid concentration of extracts were determined by using standard methods. RESULTS: All extracts inhibited nitric oxide production in a dose-dependent manner in the LPS-stimulated RAW 264.7 macrophages. Extracts of Maesa lanceolata and Heteromorpha arborescens inhibited NO production by 99.16 % and 89.48 % at a concentration of 30 µg/ml respectively. Elaeodendron croceum and Calpurnia aurea extracts had strong activity against 15-lipoxygenase activity with IC50 values of 26.23 and 34.70 µg/ml respectively. Morus mesozygia and Heteromorpha arborescens extracts had good in vitro anti-arthritic activity with IC50 values of 11.89 and 53.78 µg/ml, the positive control diclofenac sodium had IC50 value of 32.37 µg/ml. The free radical scavenging activity of the extracts in DPPH assays ranged between 7.72 and 154.77 µg/ml. Trolox equivalent antioxidant capacity (TEAC) and FRAP values ranged from 0.06 to 1.32 and 0.06 to 0.99 respectively. CONCLUSIONS: Results from this study support the traditional use of the selected medicinal plants in the management of arthritis and other inflammatory conditions. The free radical scavenging capacity of the extracts may be related to an immune boosting potential.

Antibacterial and antioxidant xanthones and benzophenone from garcinia smeathmannii.

A new prenylated xanthone, 1,3,5,8-tetrahydroxy-2-(3-methybut-2-enyl)-4-(3,7-dimethylocta-2,6-dienyl) xanthone (1), and a new benzophenone (2), together with four known xanthone derivatives, cheffouxanthone (3), smeathxanthone A (4), smeathxanthone B (5), ananixanthone (6), and two pentacyclic triterpenes, epi-friedelinol (7) and friedelin (8), were isolated from the stem bark of Garcinia smeathmannii. The structures of the compounds were elucidated on the basis of 1D and 2D NMR experiments, and compound 2 was further characterized and confirmed by single X-ray analysis. Compounds 1, 2, and 3 exhibited the most prominent antibacterial activity against gram-positive Enterococcus faecalis with minimal inhibitory concentration values of 8, 8, and 2 µg/mL, respectively, while compounds 1, 3, 4, and 6 showed the capacity to scavenge free radicals.

In vitro and in vivo antifungal activities of selected Cameroonian dietary spices.

BACKGROUND: Spices and herbs have been used in food since ancient times to give taste and flavor and also as food preservatives and disease remedies. In Cameroon, the use of spices and other aromatic plants as food flavoring is an integral part of dietary behavior, but relatively little is known about their antifungal potential.The present work was designed to assess the antifungal properties of extracts from spices used in Cameroonian dietary. METHODS: The in vitro antifungal activities of twenty three extracts from twenty one spices were assessed by the broth micro-dilution method against eight fungi. Also, the in vivo activity of Olax subscorpioidea extract (the most active extract) was evaluated in rat model of disseminated candidiasis due to Candida albicans by estimating the fungal burden in blood and kidney. RESULTS: Seven extracts (30%) exhibited moderate to significant antifungal activities, inhibiting the growth of the microorganisms at concentrations ranging from 0.048 to 0.39 mg/mL. Olax subscorpioidea extract exhibited the highest antifungal activity particularly against Candida albicans and Candida tropicalis (MIC of 0.097 mg/mL and 0.048 mg/mL respectively). Sixteen extracts (70%) were weakly active (MICs > 6.25 mg/mL). Oral administration of O. subscorpioidea extract at the dose 2 g/kg of body weight (bw) to artificially infected rats revealed a drop in the number of colony forming units per milliliter (cfu/mL) of Candida albicans cells in the blood below the detection limit (100 cfu/mL) while a modest decrease was observed in the kidney. CONCLUSION: The present work shows that some of the spices studied possess interesting antifungal properties and could be used to treat candidiasis. Among the plant species tested, Olax subscorpioidea displayed the most promising result.

Some Strychnos spinosa (Loganiaceae) leaf extracts and fractions have good antimicrobial activities and low cytotoxicities.

BACKGROUND: Strychnos spinosa Lam. is a deciduous tree used in traditional medicine to treat infectious diseases. This study is designed to determine the antimicrobial, antioxidant and cytotoxic activities of extracts and fractions from leaves of S. spinosa. METHODS: Extracts were obtained by maceration with acetone, methanol and dichloromethane/methanol (1/1) while fractions were prepared by liquid-liquid fractionation of the acetone extract. A broth serial microdilution method with tetrazolium violet as growth indicator was used to determine the minimum inhibitory concentration (MIC) against fungi, Gram-positive and Gram-negative bacteria. The antioxidant activity was determined using free-radical-scavenging assays, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to determine cytotoxicity. RESULTS: Four extracts and five fractions had good to weak antimicrobial activity with MICs ranging from 0.04 to >1.25 mg/ml against both fungi and bacteria. The chloroform and ethyl acetate fractions had an MIC of 0.08 mg/ml against Aspergillus fumigatus. The n-butanol fraction had an MIC of 0.04 mg/ml against Cryptococcus neoformans. The hexane and chloroform fractions had an MIC of 0.08 mg/ml against Staphylococcus aureus. The antioxidant activities were much lower than that of the positive controls. Except for the alkaloid extract, all the extracts and fractions had free-radical-scavenging activity (IC50 ranging from 33.66 to 314.30 µg/ml). The cytotoxicity on Vero cells was reasonable to low with LC50 values ranging between 30.56 and 689.39 µg/ml. CONCLUSION: The acetone extract and the chloroform fraction had the highest antibacterial activity. By solvent-solvent fractionation it was possible to increase the activity against A. fumigatus and to decrease the cytotoxicity leading to a potentially useful product to protect animals against aspergillosis. Our results therefore support the use of S. spinosa leaves in traditional medicine to treat infectious diseases.

Cytotoxic compounds from the leaves of Garcinia polyantha.

A new compound, named banganxanthone C (=12-(1,1-dimethylprop-2-en-1-yl)-5,10-dihydroxy-9-methoxy-2-methyl-2-(4-methylpent-3-en-1-yl)-2H,6H-pyrano[3,2-b]xanthen-6-one; 4), together with five known compounds, were isolated from the leaves of Garcinia polyantha. The structures of the compounds were elucidated on the basis of 1D- and 2D-NMR spectroscopy. Among the known compounds, two were xanthones, one was a pentacyclic triterpene, one sterol, and one benzophenone derivative. Isoxanthochymol (2) and 4-[(2E)-3,7-dimethylocta-2,6-dien-1-yl]-1,5,8-trihydroxy-3-methoxy-9H-xanthen-9-one (3) exhibited significant antiproliferative activity against the leukemia cell line TPH-1 with IC50 inhibition values of 1.5 and 2.8 µg/ml, respectively. The cytotoxic activity was found to be related to apoptosis induction.

Biofilm Formation, Pyocyanin Production, and Antibiotic Resistance Profile of Pseudomonas aeruginosa Isolates from Wounds.

Pseudomonas aeruginosa is one of the most frequently resistant and dangerous bacteria isolated from infected wounds of patients. This study aimed to determine the prevalence of P. aeruginosa from infected wounds of patients in the Dschang District Hospital to evaluate their antibiotic susceptibility profiles and their ability to swarm and swim and correlate pyocyanin production with biofilm formation. Wound swab samples were collected and the identification of P. aeruginosa was performed using microbiological and biochemical tests. Their antimicrobial susceptibility was determined by the broth microdilution method. Swarming and swimming were determined by measuring the diameters of motility in semisolid/low-viscosity media. Furthermore, pyocyanin production and biofilm formation were evaluated spectrophotometrically using a microtiter plate. The prevalence of P. aeruginosa from infected wounds in our study population was 26%. All P. aeruginosa isolates were resistant to streptomycin and paromomycin, and the frequency of multidrug resistance (MDR) was 65.8%. All P. aeruginosa isolates showed the ability to produce biofilm and pyocyanin. Out of the 37 isolates screened, 19 including the reference strains (51.4%) were strong biofilm producers. A significant positive correlation was observed among biofilm formation, pyocyanin production, and the antibiotic resistance profile of the isolates. Findings from this study suggest that infected wounds could act as a reservoir for MDR and virulent P. aeruginosa. The presence of strong biofilm producers of P. aeruginosa in infected wounds is a serious public health concern. Therefore, surveillance programs to monitor and control MDR P. aeruginosa in these patients are required to prevent their dissemination in hospital settings.

Antibiofilm Activity of Curcumin and Piperine and Their Synergistic Effects with Antifungals against Candida albicans Clinical Isolates.

Background: Candidiasis is the common name for diseases caused by yeast of the genus Candida. Candida albicans is one of the most implicated species in superficial and invasive candidiasis. Antifungals, polyenes, and azoles have been used to treat candidiasis. However, due to the development of antifungal resistance, research of natural substances with potential antifungal effects at low concentrations or combined is also a possibility. Methods: The broth microdilution method was used to evaluate the antifungal activity. The biofilm formation was assessed using the microtiter plate method. The antibiofilm activities were assessed using micro plaque tetrazolium salt assay (MTT). The combination effect of antifungal with natural substances was made using the checkerboard method. Results: Among our isolates, clotrimazole was the most resistant, but amphotericin B was the most effective antifungal. The biofilm was formed by all isolates of C. albicans. Curcumin and piperine displayed antibiofilm activity with minimum biofilm inhibitory concentration (MBIC) and minimum eradicating concentration (MBEC) ranging from 64 to 1024 µg/mL and 256 to 2048 µg/mL. In combination, piperine presented double synergistic effects compared to curcumin with all antifungals tested. Curcumin shows more synergistic effect when combined with polyenes than with azoles. However, piperine shows a more synergistic effect when combined with azoles compared to polyenes. Conclusion: C. albicans was susceptible to curcumin and piperine both on planktonic cells and biofilm. The combination of curcumin and piperine with antifungals has shown synergistic effects against multiresistant clinical isolates of Candida albicans representing an alternative drug research for the treatment of clinical candidiasis.

Synthesis, antibacterial and antibiofilm activity of new 1,2,3,5-tetrazine derivatives from coupling reactions of diazonium salt of 2-amino-6-nitrobenzothiazole with diverse substituted 2-aminobenzothiazole derivatives.

The coupling reaction of diazonium ion of 2-amino-6-nitrobenzothiazole at 0-5 °C with distinctly substituted 2-aminobenzothiazole derivatives produced new 1,2,3,5-tetrazine derivatives. It was found that diazotized 2-amino-6-nitrobenzo[d]thiazol reacts with the ring nitrogen atom of varyingly substituted 2-aminobenzothiazole derivatives to yield tetrazine nucleus. The benzene ring of benzothiazole bearing electron donor group and annelated to the tetrazine was further substituted in situ by other 6-nitrobenzo[d]thiazol-2-yl) diazinyl to yield the final product. The structure of the prepared compounds was elucidated using their physical, elemental, and spectroscopic data. The synthesized compounds were tested for their antimicrobial and antibiofilm activities against Staphylococcus aureus and Escherichia coli bacteria. Two of the synthesis tetrazine derivatives exhibited interesting antibiofilm potential.

Pyrroloquinolones B-F: Five unusual alkaloids from Vernonia glabra (Steetz) Vatke (Asteraceae).

Five unusual alkaloids featuring a pyrrolo[1,2-a]quinolone skeleton (pyrroloquinolones B-F, 1-5) were isolated from the ethanol extract of the whole plant of Vernonia glabra (Steetz) Vatke, along with sixteen known compounds. Their structures were established by means of spectroscopic (1D and 2D NMR, UV, IR, and ECD) and high resolution mass spectrometric techniques as well as by comparison of their spectroscopic data with those reported in the literature. The ethanol extract and some isolated compounds were assessed for their antibacterial activity against four bacterial strains. The extract was significantly active against Staphylococcus aureus ATCC1026 and S. epidermidis ATCC35984 (MIC = 64 µg/mL). All the tested compounds showed moderate activity against S. epidermidis (16 ≤ MIC ≤ 64 µg/mL). Furthermore, this is the first report on tricyclic pyrrolo[1,2-a]quinolone alkaloids from a plant source. A biosynthetic pathway for the formation of these compounds is also proposed.

Naturally occurring benzophenones and xanthones from Garcinia smeathmannii (Planch. & Triana) Oliv. displayed anti-inflammatory effects by modulating the activities of inflammatory mediators in LPS-stimulated RAW 264.7 macrophages.

Introduction: There is a growing interest in studying natural products for the identification of novel lead compounds for drug development for treating inflammatory diseases. Although some studies have focused anti-inflammatory activity of benzophenones and xanthones, exploring additional targets such as enzymes and cytokines, involved in their inflammatory response could provide more comprehensive understanding of the compounds' anti-inflammatory effects. In this study, four xanthones ananixanthone (1), smeathxanthone A (2), smeathxanthone B (3), and 1,3,5,8-tetrahydroxy-2-(3-methybut-2-enyl)-4-(3,7-dimethyloct-2,6-dienyl) xanthone (4); and three benzophenones guttiferone O (5), guttiferone M (6), and aristophenone A (7) from Garcinia smeathmannii (Planch. & Triana) Oliv. were investigated for their effect on nitric oxide production, cyclooxygenase, lipoxygenase inhibition, and Th1/Th2 cytokines production in activated RAW 264.7 macrophages. Methods: The Griess reagent method and the ferrous oxidation-xylenol orange assay were used to evaluate the inhibition of NO production and the 15-lipoxygenase activity respectively. Cyclooxygenase activity was assessed using the fluorometric COX activity assay kit and measurement of Th1/Th2 cytokines was performed using a flow cytometer. Results: All the tested compounds exhibited a dose-dependent inhibition of NO production with varying degrees of inhibitory effects on 15-LOX activity. Compound (6), displays the best inhibitory effect on COX-1/COX-2 activity. A general trend of the tested compounds on cytokines profiles revealed that compound (5) showed a pronounced enhancement of anti-inflammatory cytokines (IL-4 and IL-10). Conclusion: This observation supports future exploration of ananixanthone (1), guttiferone O (5), and guttiferone (6) as potential candidates for the development of anti-inflammatory drugs.

Cytotoxic and antimicrobial activity of selected Cameroonian edible plants.

BACKGROUND: In Cameroon, the use of edible plants is an integral part of dietary behavior. However, evidence of the antimicrobial as well as the cytotoxic effects of many of them has not been investigated. In the present study, aqueous and methanol extracts from barks, seeds, leaves and roots of three Cameroonian edible plants namely Garcina lucida, Fagara heitzii and Hymenocardia lyrata were evaluated for their cytotoxic and antimicrobial activities. METHODS: Antibacterial and antifungal activities were assessed by the broth micro-dilution method meanwhile the cytotoxicity was performed using sulphorhodamine B assay (SRB) against the human leukemia THP-1, the alveolar epithelial A549, prostate cancer PC-3, breast adenocarcinoma MCF-7 and cervical cancer HeLa cell lines. RESULTS: The minimum inhibitory concentration (MIC) values of the seven tested extracts ranged from 62.5 µg/ml to 1000 µg/ml. The methanol (MeOH) extract from the roots of H. lyrata showed the highest antibacterial activity against Gram-positive bacteria S. aureus and S. epidermitis. The best antifungal activity was obtained with the MeOH extract from the leaves of G. lucida against C. tropicalis (MIC value of 62.5 µg/ml). The in vitro antiproliferative activity revealed that, extract from the bark of F. heitzii and extract from H. lyrata roots had significant cytotoxic activity on THP-1 (IC50 8.4 µg/ml) and PC-3 (IC50 9.5 µg/ml) respectively. CONCLUSION: Our findings suggest that Cameroonian spices herein studied could be potentially useful for the development of therapeutic agents against bacterial infections as well as for prostate and leukemia cancer.