Antimicrobial Activity Of Secondary Metabolites Research Articles

Antimicrobial metabolites from Probiotics, Pleurotus ostreatus and their co-cultures against foodborne pathogens isolated from ready-to-eat foods

BackgroundThe incidence of foodborne pathogens in ready- to-eat (RTE) can be attributed to various foodborne diseases. Most of the isolated microorganisms from RTE foods are resistant to common antibiotics and thus, resulted to treatment failure when commercially available antibiotics are administered. However, the secondary metabolites secreted by microorganisms can serve as alternative therapy that are reliable and safe. Secondary metabolites obtained from mono- and co-culture microorganisms can inhibit the growth of antibiotic-resistant microorganisms. Bioactive compounds in the secreted metabolites can be identified and utilized as sources of new antibiotics. In this study, antimicrobial activity of secondary metabolites from Lactobacillus fermentum, Saccharomyces cerevisiae, Pleurotus ostreatus, and their co-cultures were tested against foodborne pathogens isolated from RTE foods using agar well diffusion. The bioactive compounds in the metabolites were identified using gas chromatography-mass spectrometry.ResultsFrom a total of 100 RTE foods examined, Salmonella enterica, Shigella dysenteriae, Escherichia coli, Klebsiella pneumoniae (subsp ozaenae), Pseudomonas fluorescens, Clostridium perfringes, Bacillus cereus, Listeria monocytogens, and Staphylococcus aureus, Penicillium chrysogenum, Aspergillus flavus, and Aspergillus niger were isolated and displayed multiple antibiotic resistance. The secondary metabolites secreted by co-culture of L. fermentum + P. ostreatus + S. cerevisiae, and co-culture of P. ostreatus + S. cerevisiae have the highest (P ≤ 0.05) zones of inhibition (23.70 mm) and (21.10 mm) against E. coli, respectively. Metabolites from mono-cultured L. fermentum, P. ostreatus, and S. cerevisiae showed zones of inhibition against indicator microorganisms with values ranging from 8.80 to 11.70 mm, 9.00 to 14.30 mm, and 9.30 to 13.00 mm, respectively. Some of the bioactive compounds found in the metabolites of co-cultured microorganisms were alpha-linolenic acid (25.71%), acetic acid 3-methylbutyl ester (13.83%), trans-squalene (12.39%), pentadecylic acid (11.68%), 3- phenyllactic acid (30.13%), linolelaidic acid methyl ester (15.63%), and 4-O-methylmannose (53.74%).ConclusionRTE foods contain multiple antibiotics resistance pathogens. The pronounced antimicrobial activity of the secondary metabolites against microorganisms from RTE foods could be attributed to the presence of bioactive compounds in the metabolites. These metabolites can be exploited as alternative food preservatives, biopharmaceuticals and can be used towards better health delivering systems.

Isolation and antimicrobial activity of secondary metabolites of pothos tener wall

The Pothos genus is extensively utilised in traditional medicine in China and India. An underexplored species of Pothos tener Wall was identified in Sulawesi, Indonesia. Antimicrobial activity was assessed using microdilutions and streak plates against Staphylococcus aureus, Eschericia coli, Aeromonas hydrophila, Aspergillus niger, and Candida albicans. Significant effectiveness was observed in the methanol extract, as indicated by the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values for three different extracts (methanol, ethyl acetate, and n-hexane) of P. tener. The isolates obtained were structurally analysed using Ultraviolet (UV)-spectroscopy, Fourier-transform Infra Red-Spectroscopy (FT-IR), Mass Spectroscopy (MS), Nuclear Magnetic Resonance (NMR), and antimicrobial testing after undergoing fractionation and subfractionation. The isolate obtained was stigmasterol with moderate antimicrobial activity against A. niger and A. hydrophila, with MIC equivalent to MBC of 500 µg/ml. The first report of stigmasterol from P. tener has potent antimicrobial properties, bolstering empirical data in this field.

Antioxidant, anticancer and antimicrobial activity of secondary metabolites from Fusarium species

To evaluate the biological activities of secondary metabolites obtained from Fusarium species. The secondary metabolites of Fusarium oxysporum showed a proliferative effect on MCF-7 cells. The secondary metabolites of Fusarium solani reduced the viability of the MCF-7 cell in 48 hours. The metabolites of both fungi showed significant antibacterial activity (p<0.0010) in E. coli strains at all concentrations. F.oxysporum and solani significantly inhibited S. aureus at all concentrations within 24h. F. oxysporum metabolites significantly reduced C. albicans at all concentrations within 24h. The secondary metabolites of Fusarium solani significantly (p<0.0001) reduced the viability of C. albicans at all concentrations. There are compounds in Fusarium solani with antitumor and antimicrobial properties.

Antimicrobial Activity of Secondary Metabolites in Medicinal Plants: An Update

Plants have filled in as a significant wellspring of elements for conventional drugs for centuries. Verifiable records and present day ethno botanical field examines feature their significance in the conventional treatment of irresistible malady. Be that as it may, plants form just a minor level of present collection of FDA-endorsed antimicrobial medications. The present article gives an outline of active components of plants as hint for other wellspring of antimicrobial agents to be used in the battle against microscopic organisms. It additionally surveys the ethno botanical way to deal with sedate disclosure and talks about various inventive focuses for future medication revelation endeavours in this field. Without an uncertainty, antimicrobials are miracle tranquilizers. They have represented a very long time against different irresistible infections and spared a huge number of lives. The ongoing disappointment of antimicrobials because of the sensational rise of multidrug-safe microbes and fast spread of new diseases, be that as it may, prompts wellbeing associations and the pharmaceutical business worldwide to change their methodology and to expand improvement of antimicrobials against quickly rising anti-infection safe microorganisms. In spite of the fact that there is thinking about elective wellsprings of characteristic antimicrobial molecules from plants having different methods of activity, some of which have been utilized in regular medication for a considerable length of time and have appeared to have serious impacts contrasted with other antimicrobials. This examination portrays plant intensity as an elective hotspot for antimicrobial agents.

Enhanced Antimicrobial Activity through Synergistic Effects of Cold Atmospheric Plasma and Plant Secondary Metabolites: Opportunities and Challenges.

The emergence of antibiotic resistant microorganisms possesses a great threat to human health and the environment. Considering the exponential increase in the spread of antibiotic resistant microorganisms, it would be prudent to consider the use of alternative antimicrobial agents or therapies. Only a sustainable, sustained, determined, and coordinated international effort will provide the solutions needed for the future. Plant secondary metabolites show bactericidal and bacteriostatic activity similar to that of conventional antibiotics. However, to effectively eliminate infection, secondary metabolites may need to be activated by heat treatment or combined with other therapies. Cold atmospheric plasma therapy is yet another novel approach that has proven antimicrobial effects. In this review, we explore the physiochemical mechanisms that may give rise to the improved antimicrobial activity of secondary metabolites when combined with cold atmospheric plasma therapy.

Deciphering the Antimicrobial Potential of Taxus wallichiana Zucc: Identification and Characterization Using Bioassay-Guided Fractionation.

Taxus wallichiana Zucc. is a high valued medicinal plant and has been mainly studied for its anti-cancer properties. However, research on its other important biological activities, such as its antimicrobial potential, still needs attention. The focus of the present study is to investigate the antimicrobial activity of secondary metabolites of T. wallichiana needles against 3 different groups of microorganisms, i. e., bacteria, actinobacteria, and fungi. Bioactive compounds from T. wallichiana needles were separated through column chromatography, and, TLC-bioautography. Mobile phases were optimized using Snyder's selectivity triangle. Antimicrobial spots were fractionated and compounds were identified by gas chromatography-mass spectroscopy (GC/MS) and liquid chromatography-mass spectrometry (LC/MS). Functional groups were characterized using Fourier transform infrared spectrometry (FTIR) and nuclear magnetic resonance (NMR) was used to identify the molecular structures. GC/MS and LC/MS data analysis confirm the presence of fatty acids (arachidic acid, behenic acid, palmitic acid, and stearic acid), vitamins (nicotinamide), and alkaloids (cinchonine, timolol), aminobenzamides (procainamide), carbocyclic sugar (myoinositol), and alkane hydrocarbon (hexadecane), having antimicrobial activity in the needles of T. wallichiana. To the best of our knowledge, this is the first report on the isolation and characterization of antimicrobial compounds from the needles of Taxus wallichiana (Himalayan yew). The data obtained from the present study will be supportive to the new drug discoveries in modern medicine with various combinations of medicinal plant's active constituents that can be used for curing many diseases.

Antimicrobial Activities of Secondary Metabolites from Model Mosses.

Plants synthetize a large spectrum of secondary metabolites with substantial structural and functional diversity, making them a rich reservoir of new biologically active compounds. Among different plant lineages, the evolutionarily ancient branch of non-vascular plants (Bryophytes) is of particular interest as these organisms produce many unique biologically active compounds with highly promising antibacterial properties. Here, we characterized antibacterial activity of metabolites produced by different ecotypes (strains) of the model mosses Physcomitrium patens and Sphagnum fallax. Ethanol and hexane moss extracts harbor moderate but unstable antibacterial activity, representing polar and non-polar intracellular moss metabolites, respectively. In contrast, high antibacterial activity that was relatively stable was detected in soluble exudate fractions of P. patens moss. Antibacterial activity levels in P. patens exudates significantly increased over four weeks of moss cultivation in liquid culture. Interestingly, secreted moss metabolites are only active against a number of Gram-positive, but not Gram-negative, bacteria. Size fractionation, thermostability and sensitivity to proteinase K assays indicated that the secreted bioactive compounds are relatively small (less than <10 kDa). Further analysis and molecular identification of antibacterial exudate components, combined with bioinformatic analysis of model moss genomes, will be instrumental in the identification of specific genes involved in the bioactive metabolite biosynthesis.

Antimicrobial Activity of Secondary Metabolites Isolated from Endophytic Fungi Associated with Rubiaceae Species

The effectiveness of antibiotics has declined significantly due to development of drug resistance. Consequently, it results in millions of deaths due to infectious diseases. Many studies have suggested that bioactive compounds produced by endophytes could be an alternative to discover new antimicrobial compounds. Endophytes are microorganisms that reside within the tissues of living plants that cause no apparent harm to the host. Fungal endophytes may biosynthesize the same or similar compounds as their host plant and other diverse bioactive compounds, which provide various pharmacological activities. Therefore, this study aimed to conduct literature search on the antimicrobial properties of the isolated compounds produced by fungal endophytes associated with Rubiaceae. Literature was conducted on secondary metabolites of endophytic fungi via four databases; EBSCOhost, Google Scholar, PubMed, and Scopus. A search filter was performed to include only research articles from 2007 to 2021. The search was restricted to publications in English only. Overall, 29 publications were selected for full-text evaluation and were included in the study. Results showed that sixteen antimicrobial metabolites were isolated from six fungal endophytes of ten different plant species were identified. These compounds were classified as alkaloid, phenol, coumarin, steroid, diterpene, and meroterpene.

Isolation of Actinobacteria Strains From Environmental Samples and Assessment of Their Bioactivity

Background: Actinobacteria are widespread and live in a variety of habitats. Today, these bacteria are very important due to the production of various secondary metabolites with different biological activities. The present study aimed to isolate strains of Actinobacteria from different habitats (the Persian Gulf, Gandom Beryan area in the Lut Desert, and some plant roots). The anticancer and antimicrobial activities of secondary metabolites of these isolates were also investigated. Methods: Samples were taken from water of the Persian Gulf, soil of Gandom Beryan area in the Lut Desert, and plant roots. For isolation of Actinobacteria, samples were cultured in ISP2, ISP4, AIA, Gauze, M1, ISP3, and GYP media. Bacterial strains were identified based on the colony and bacterial morphology and confirmed using the specific primers for Actinobacteria. The anticancer and antimicrobial activities of crude metabolite extracts and supernatant of the isolates were evaluated on MCF-7 and Staphylococcus aureus PTCC 112 and Pseudomonas aeruginosa PTCC 1214 strains. Results: The results showed that the supernatants of 7 isolates (ga31, ez, sa, mar2, rz, ga33, and ga5) and the metabolite extracts of 4 strains (ga31, ga5, rz, and ez) had anticancer activity. Overall, ga31 was the best strain with anticancer activity of more than 75%. When evaluating the antimicrobial activity of bacterial secondary metabolites, we found that only two strains (ga31 and ga5) had antimicrobial activity against S. aureus PTCC 1112. Conclusions: In general, strain ga31, which has high anticancer and antimicrobial activities, could be a good candidate for new trials in the pharmaceutical industry.

Antimicrobial Activity of Secondary Metabolites from Endophytic Fungus Fusarium sp. Isolated from Eichhornia crassipes Linn.

The active metabolites producing endophytic fungus, Fusarium sp., was isolated from Eichhornia crassipes Linn. yielded four compounds: “altersolanol (1)”, “4-hydroxydihydronorjavanicin (2)”, “5-hydroxy-7-methoxy-2-isopropylchromone (3)” and “fusaraichromenone (4)”. Structures of 1-4 were elucidated by analysis of their spectroscopic data. The antimicrobial activity was tested by using four bacteria; methicillin-resistant Staphylococcus aureus (MRSA SK1), Staphylococcus aureus (SA), Escherichia coli (EC) and Pseudomonas aeruginosa ATCC27853 (PA)and two yeast; Cryptococcus neoformans ATCC90112 flucytosine – resistant (CN90112) and Candida albicans ATCC 90028 (CA90028) to adverse effect showed that compound 1 and 3 had moderate antibacterial activity against MRSA, SA, PA and SK1 with same MIC value 16 μg/mL. However, all pure compounds showed relatively low activities to inhibit the growth of CA90028 and CN91112 yeast.

Antimicrobial activity of secondary metabolites of endophytic bacteria F4 of papaya leaf (Carica papaya L)

Papaya leaves have been known to contain secondary metabolite compounds as antimicrobial, so that endophytic bacteria is also suspected of having secondary metabolite compounds as antimicrobial. In previous research, endophytic bacteria have been isolated from papaya leaf and obtained 5 endophytic bacteria which were F1, F2, F3, F4 and F5. Three bacterias that have been known for their antibacterial activity were F1, F3, and F5. This research aims to determine the antimicrobial activity of F4 endophytic bacteria. The results showed that single isolates of endophytic bacteria F4 is a type of Gram-positive bacteria with a basil cell shape (stem). F4 endophytic bacteria has 3 growth phases; they are logarithmic phase occurs at 0-8 hours, stationary phase at 8-34 hours, and phase of death at 34-46 hours. Phytochemical results showed that MS18 contained saponin group compounds, while MS36 contained alkaloids and saponin group compounds. The highest antimicrobial activity was in the death phase, MS36 with minimum inhibitory concentration (KHM) to Escherichia coli, Candida albicans, and Bacillus subtillis were 15.5 mg/mL, respectively; 16.5 mg/mL and 16.5 mg/mL by disc diffusion method, whereas to Aspergillus niger of 0.5 mg/mL by dry weight method.

Cytotoxic and antimicrobial activities of secondary metabolites isolated from the deep-sea-derived Actinoalloteichus cyanogriseus 12A22.

The online version contains supplementary material available at 10.1007/s13205-021-02846-0.

Antimicrobial Potential of Naturally Occurring Bioactive Secondary Metabolites.

The use of traditional medicines of natural origin has been prevalent since ancient times globally as the plants produce a great diversity in their secondary metabolites. The naturally occurring bioactive constituents in food and other plant materials have shown widespread attention for their use as alternative medicine to prevent and cure microbial growth with the least toxic manifestations. The inclusion of these contents revealed their crucial role to improve the therapeutic efficacy of the classical drugs against various pathogenic microorganisms. Furthermore, several metabolites have also been explored in combination with antimicrobial agents to overcome the problems associated with drug resistance. This current review discusses the antimicrobial activities of secondary metabolites as well as their role in drug sensitivity against multiple-drug resistant pathogenic microbes.

Antimicrobial activity of secondary metabolites produced by Aspergillus neobridgeri isolated from Pistacia lentiscus against multi-drug resistant bacteria

The in vitro antibacterial activity of the endophytic fungus Aspergillus neobridgeri PLR9 (isolated from the plant Pistacia lentiscus) against a wide range of tested bacteria were studied. The maximum inhibitory activity was found on malt extract agar medium with a mean inhibitory zone of 11.3 mm (p&lt;0.05). The ethyl acetate extract showed a significant inhibitory zone of 13.4 mm (p&lt;0.05), followed by dichloromethane 9.1 mm. Whereas, n-hexane extract showed no activity. The largest inhibition zones were observed against Staphylococcus aureus 3, S. aureus 5 and Escherichia coli 1 with 21.0 mm of diameter. The MIC's were ranged between 312.5 and 1,250 μg/mL. The MBC's were ≤2500 μg/mL for most Gram positive bacteria and ≥2500 μg/mL for most Gram negative bacteria. Time kill assay study against the Enterococcus faecium showed a bactericidal effect at 4x MIC and bacteriostatic against Acinetobacter baumannii at different concentrations. Moreover, it is the first report, PLR9 isolated as endophyte and studied for their antimicrobial activity.

Actividad antimicrobiana de metabolitos secundarios de Aspergillus fumigatus sensu stricto sobre cepas clínicas de Staphylococcus aureus y Streptococcus pneumoniae

Introducción. La resistencia a los antibióticos de bacterias Gram positivas es un grave problema de salud pública donde algunas medidas paliativas pueden encontrarse en los principios antimicrobianos de hongos filamentosos. Objetivo. Evaluar la actividad antimicrobiana de metabolitos secundarios de un aislamiento clínico de Aspergillus fumigatus sobre cepas clínicas de Staphylococcus aureus y Streptococcus pneumoniae. Métodos. La fermentación líquida de A. fumigatus se realizó en un caldo líquido sulfato, papa y dextrosa, utilizando acetato de etilo para la extracción de metabolitos. Mediante la metodología de disco difusión se evaluó la actividad antimicrobiana considerada como un halo mayor de 6 mm. Resultados. Se obtuvo una media de 24,02 ± 2,51 mm y 23,62 ± 4,68 mm de halo de inhibición sobre Staphylococcus aureus sensible y resistente oxacilina, respectivamente. Para Streptococcus pneumoniae sensibles y no sensibles a penicilina las medias fueron de 25,82 ± 4,05 mm y 26,5 ± 5,39 mm, respectivamente. Conclusiones. El extracto crudo de A. fumigatus posee metabolitos secundarios de naturaleza alcaloide y esteroles insaturados con actividad antimicrobiana.

Isolation, identification and antimicrobial activity of secondary metabolites of endophytic fungi from annona leaves (Annona squamosa L.) growing in dry land

Research on isolation, identification, and antimicrobial activity of secondary metabolites of endophytic fungi from leaves of Annona squamosa growing in dryland had been undertaken. The work includes the isolation of endophytic fungi, cultivation, and extraction of fungal extract and identification of chemical metabolites together with the antibacterial test. The pure colony of endophytic fungi was grown on solid rice media using 1 L Erlenmeyer flask. The grown fungi were extracted with ethyl acetate. The ethyl acetate crude extract was then further subjected to chemical analysis and its antibacterial properties. Endophytic fungi species was identified as Aspergillus niger based on macroscopic and microscopic analysis. Analysis LC-MS/MS had revealed the presence of five metabolites including ephedradine A, ergosine, Ia, mudanpioside H, and trichosanic acid. The extract showed strong inhibition against Staphyloccus aureus with diameter of zone inhibition of 16.1 mm and moderate inhibition against Escherichia coli 0175H7 and Salmonella enteritidis ATCC 6939 with the observed diameter of zone inhibition of 9.6 mm and 11.3 mm, respectively.

Inhibitory Effect and Antimicrobial Activity of Secondary Metabolites of &amp;lt;i&amp;gt;Khaya Senegalensis&amp;lt;/i&amp;gt; (Desr.) A. Juss. (Meliaceae)

This present study investigates the in vitro inhibitory effect and antimicrobial activity of secondary metabolites isolated from the roots of Khaya senegalensis, a plant of the Meliaceae family. Khaya senegalensis is widely used in traditional medicine for the treatment of various illnesses such as: fever, stomach ache, diarrhea, dysentery and anemia. The chemical study of the extract with CH2Cl2-MeOH (1:1) led to the isolation of five compounds: Alphitolic acid (1); Epigouanic acid (2); Methyl angolensate (3); Rohituca-3 (4) and 5, 6, 7, 3′, 4′-pentamethoxyflavone or Sinensetin (5). Alphitolic acid (1), Rohituca-3 (4) and 5, 6, 7, 3′, 4′-pentamethoxyflavone or Sinensetin (5) were isolated from the roots of this plant for the first time. The structures of the isolated compounds have been elucidated on the basis of spectroscopic analysis and a comparison of their spectral data with those reported in the literature. The results of the antibiogram tests showed that the strain of Escherichia coli is sensitive to all the antibiotics tested except Ceftazidime, a Cephalosporin. The Staphylococcus aureus strain is resistant to almost all the antibiotics tested except Amikacin, an aminoglycoside. This is because the enzymes diffuse through the inter and intraspecific transmission of genes through a plasmid. The antibiogram made it possible to establish the sensitivity profile of the strains tested with regard to certain antibiotics. The antimicrobial tests carried out showed that the inhibitory effect of the compounds isolated from Khaya senegalensis on the four bacterial strains tested at the concentration of 25 mg/mL positively influenced at least one of the microbial strains. However, compounds 1, 2 and 3 did not show any bacterial growth inhibitory activity against Proteus vulgaris. MIC obtained for microbiological tests varied between 0.097 and 0.195 mg/mL for the most sensitive strains of Escherichia coli and Pseudomonas aeruginosa, which revealed the highest antibacterial powers. Furthermore, these results therefore show a great variability in the bacteriostatic qualities of the compounds with respect to the different strains. The two Gram-positive strains of Staphylococcus aureus are more sensitive than the other Gram-negative bacterial strains tested. From the antibacterial activity, it appears that the compounds isolated from this plant have a bactericidal activity against Escherichia coli and Pseudomonas aeruginosa. This bactericide could justify their use in herbal medicine against bacterial infections.

Broad-spectrum antimicrobial activity of secondary metabolites produced by Serratia marcescens strains

The genus Serratia is a predominantly unexplored source of antimicrobial secondary metabolites. The aim of the current study was thus to isolate and evaluate the antimicrobial properties of biosurfactants produced by Serratia species. Forty-nine (n = 34 pigmented; n = 15 non-pigmented) biosurfactant producing Serratia strains were isolated from environmental sources and selected isolates (n = 11 pigmented; n = 11 non-pigmented) were identified as Serratia marcescens using molecular typing. The swrW gene (serrawettin W1 synthetase) was detected in all the screened pigmented strains and one non-pigmented strain and primers were designed for the detection of the swrA gene (non-ribosomal serrawettin W2 synthetase), which was detected in nine non-pigmented strains. Crude extracts obtained from S. marcescens P1, NP1 and NP2 were chemically characterised using ultra-performance liquid chromatography coupled to electrospray ionisation mass spectrometry (UPLC-ESI-MS), which revealed that P1 produced serrawettin W1 homologues and prodigiosin, while NP1 produced serrawettin W1 homologues and glucosamine derivative A. In contrast, serrawettin W2 analogues were predominantly identified in the crude extract obtained from S. marcescens NP2. Both P1 and NP1 crude extracts displayed broad-spectrum antimicrobial activity against clinical, food and environmental pathogens, such as multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and Cryptococcus neoformans. In contrast, the NP2 crude extract displayed antibacterial activity against a limited range of pathogenic and opportunistic pathogens. The serrawettin W1 homologues, in combination with prodigiosin and glucosamine derivatives, produced by pigmented and non-pigmented S. marcescens strains, could thus potentially be employed as broad-spectrum therapeutic agents against multidrug-resistant bacterial and fungal pathogens.

Molecular Identification and Antimicrobial Activity of Vaginal Lactobacillus sp.

The genus Lactobacillus has recently been the focal point of researchers due to their ability to produce secondary metabolites with antimicrobial effects. The aim of this study was to identify vaginal Lactobacillus sp. by analyzing 16S rRNA gene sequence, to investigate into antimicrobial activities of secondary metabolites produced by these isolates and to determine the quantities of lactic acid, acetic acid and hydrogen peroxide in secondary metabolites using High-Performance Liquid Chromatography. Antimicrobial activities of secondary metabolites were investigated against test microorganisms using Agar Well Diffusion and Agar Spot Methods. According to the results, 18 L. crispatus, 17 L. gasseri, 5 L. jensenii, 4 L. vaginalis, 3 L. fermentum, 2 L. coleohominis, 1 L. saerimneri, 1 L. reuteri, 1 L. johnsonii and 1 L. helveticus were identified. Isolates were frequently found to be effective against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae RSKK 578 and Bacillus subtilis ATCC 6633. None of the isolates showed activity against Staphylococcus aureus ATCC 43300, S. epidermidis ATCC 12228, S. epidermidis ATCC 35984 and Candida albicans ATCC 10231. Secondary metabolites of all tested isolates contain hydrogen peroxide between 7.306 and 0.33 µg/µL range. It was found that the secondary metabolites of some isolates contained both acetic and lactic acid, while some of them contained either acetic or lactic acid.

Evaluation of antimicrobial activity of secondary metabolites of fungi isolated from Sultanate Oman soil

Seven fungal species were isolated from soil samples collected from the University of Sultan Qaboos, Muscat, Sultanate of Oman. The fungal isolates were identified as Aspergillus athecius, A. terreus var. africans, A. flavus, A. terreus, A. foetidus, Fusarium chlamydosporum and F. nygamai. Phytochemical and chromatographic investigation showed variety of secondary metabolites in all of the fugal extracts (extra and intra cellular). The antimicrobial activity of internal and external extracts of the isolated fungal species were screened against Candida albicans, C. glabrata, C. parapsilosis, C. tropicalis, Pseudomonas aeruginosa, Lactobacillus acidophilus, Streptococcus gordonii, S. mutans. The antimicrobial activity of external secondary metabolites was generally better than the internal metabolites. The highest antimicrobial activity (32 mm, 30 mm and 29 mm) was obtained from external secondary metabolites of Aspergillus flavus against Candida tropicals, Candida parapsilosis and Candida albicans, respectively.