Effect of Cymbopogon martinii, Foeniculum vulgare, and Trachyspermum ammi Essential Oils on the Growth and Mycotoxins Production by Aspergillus Species

Antibacterial and Antifungal Activities of Ethiopian Medicinal Plants: A Systematic Review

Background: Podoconiosis and lymphatic filariasis are the most common causes of lower limb lymphoedema in the tropics. Many sufferers experience frequent painful episodes of acute bacterial infection. Plant based traditional medicines are used to treat infections in many countries and are culturally established in Ethiopia. Ethiopian medicinal plants found to have antibacterial and antifungal activities were reviewed with the aim of increasing information about the treatment of wound infections in patients with lymphoedema. Methods: This study collates data from published articles on medicinal plants with antibacterial and antifungal activities in Ethiopia. A systematic search of Scopus, EMBASE, PUBMED/MEDLINE and Google Scholar was undertaken. The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines were followed. The protocol was registered on PROSPERO with registration number CRD42019127471. All controlled studies of in vitro antibacterial and antifungal activities were considered. All articles containing the descriptors published until June 28, 2019 were included. The outcome was measured as percent inhibition of microbial growth. For quality assessment of individual in vitro studies, OECD guidelines and the WHO-Good Laboratory Practice (GLP) handbook were used. Results: Seventy-nine studies met the inclusion criteria. A total of 150 plant species and three compounds had been tested against 42 species of bacteria, while 43 plant species had been tested against 22 species of fungus. Conclusion: Materials derived from several Ethiopian medicinal plants have been shown to have promising activity against a variety of bacteria and fungi. Those derived from Azadiractha indica A. Juss. and Lawsonia inerms L. are the most extensively studied against a wide range of gram-negative and positive bacteria, and fungal species.

Recent advances on the efficacy of essential oils on mycotoxin secretion and their mode of action

Essential oils, as extracted compounds from plants, are volatile and aromatic liquids which their unique aromatic compounds give each essential oil its distinctive essence. Fungi toxins can induce various adverse health effects like allergy, cancer, and immunosuppression. Moreover, fungal spoilage impacts pharmaceutical and food industries economic state. A drop in the utilization of synthetic compounds as food prophylaxis has occurred due to several factors such as hygiene agents' alerts and stricter legal regulations. Therefore, the applications of natural substances such as essential oils have increased in recent years. Oregano, cinnamon, thyme, rosemary, fennel, clove, palmarosa, and eucalyptus have been the highest employed essential oils against mycotoxigenic fungi and their mycotoxins in studies conducted in the past decade. Essential oils inhibit fungi growth and mycotoxin synthesis via diverse pathways including modified fungal growth rate and extended lag phase, disruption of cell permeability, disruption of the electron transport chain and manipulating gene expression patterns and metabolic processes. In the present review, we will investigate the implications and efficacy of essential oils in preventing the growth of mycotoxigenic fungi, eliminating mycotoxins and their mechanism of actions conducted in the last decade. HighlightsThe most investigated toxigenic genera are Aspergillus, Fusarium and Penicillium Spp.AB1, AG1, OTA and AB2 are the most frequently studied toxinsOregano, cinnamon and thyme are mostly exploited EOs on toxigenic fungi & mycotoxinsOregano, thyme & cinnamon are the most significant antifungals on toxigenic generaCinnamon, oregano & cinnamaldehyde are the fittest antimycotoxins on DON, OTA & AFB1.

Multidrug and Pan-Antibiotic Resistance—The Role of Antimicrobial and Synergistic Essential Oils: A Review

Bacterial resistance to antibiotics continues to be a grave threat to human health. Because antibiotics are no longer a lucrative market for pharmaceutical companies, the development of new antibiotics has slowed to a crawl. The World Health Organization reported that the 8 new bacterial agents approved since July 2017 had limited clinical benefits. While a cohort of biopharmaceutical companies recently announced plans to develop 2-4 new antibiotics by 2030, we needn’t wait a decade to find innovative antibiotic candidates. Essential oils (EOs) have long been known as antibacterial agents with wide-ranging arsenals. Many are able to penetrate the bacterial membrane and may also be effective against bacterial defenses such as biofilms, efflux pumps, and quorum sensing. EOs have been documented to fight drug-resistant bacteria alone and/or combined with antibiotics. This review will summarize research showing the significant role of EOs as nonconventional regimens against the worldwide spread of antibiotic-resistant pathogens. The authors conducted a 4-year search of the US National Library of Medicine (PubMed) for relevant EO studies against methicillin-resistant Staphylococcus aureus, multidrug-resistant (MDR) Escherichia coli, EO combinations/synergy with antibiotics, against MDR fungal infections, showing the ability to permeate bacterial membranes, and against the bacterial defenses listed above. EOs are readily available and are a needed addition to the arsenal against resistant pathogens.

Development, Characterization, and Evaluation of Novel Broad-Spectrum Antimicrobial Topical Formulations from Cymbopogon martini (Roxb.) W. Watson Essential Oil

Background

Skin infections were the most frequently encountered of all infections and the 4th leading cause of nonfatal disease burden. Topical drugs have been used for the management of skin infections. The growing concern of drug resistance to the topical agents has warned the need for continuous development of novel drug. Essential oils are the best candidate for new drug with different mode of action and target as they are rich in chemical constituents.

Objective

To evaluate and develop safe and effective topical antimicrobial formulations from essential oil of Cymbopogon martini. Method. Essential oil was extracted using hydrodistillation aerial part C. martini and topical formulations were prepared in five different semisolid bases. In vitro antimicrobial investigations were performed on essential oil and topical formulations. Skin sensitizations of the formulations were evaluated using guinea pig maximization.

Results

The essential oil of C. martini has shown broad-spectrum antimicrobial potency against all tested organisms with MIC value ranging from 0.65 to 10 μg/ml. Absolute inhibitions of growth of fungi were observed against Trichophyton mentagrophytes and Trichophyton rubrum at concentrations above 1% of oil and against Microsporum canis and Trichophyton verrucosum at a concentration of 4% oil. Among topical formulations, the highest antimicrobial activity was recorded in hydrophilic ointment followed by macrogol blend ointment. The antimicrobial activity of oil was higher in fungal pathogen compared to bacteria. Gram positive bacteria were more sensitive than gram negative bacteria. Hydrophilic and macrogol blend ointment containing 5% oil did not produce any skin sensitization on guinea pigs.

Conclusion

In conclusion, topical formulations of C. martini essential oil can be alternative topical agents with safe broad-spectrum activity for the treatment of skin disorder. Further studies should focus on shelf life study and clinical study of the product.

Efficacy of chemically characterized Foeniculum vulgare Mill seed essential oil in protection of raw tobacco leaves during storage against fungal and aflatoxin contamination

AIMS

To report fungal and aflatoxin contamination in stored tobacco leaves and the potential of Foeniculum vulgare (fennel) seed essential oil (EO) as a plant-based preservative in protection of tobacco during storage.

METHODS AND RESULTS

Mycological analysis of tobacco samples was done by surface sterilization and serial dilution tests. The Aspergillus flavus isolates were screened for their toxigenicity. Both in vivo and in vitro tests were done to evaluate antifungal and antiaflatoxigenic efficacy of chemically characterized EO. The mycoflora analysis revealed 108 fungal colonies belonging to five genera and nine species. All A. flavus isolates were found aflatoxigenic during screening. Gas chromatography and mass spectrometry analysis of EO identified 19 components (99·66%); estragole being the major component (47·49%). The EO showed broad fungitoxicity at 1·25 μl ml(-1) and 100% inhibition to AFB1 production as well as ergosterol synthesis at 1·0 μl ml(-1) concentration. EO showed 100% protection of stored tobacco samples from aflatoxin B1 contamination.

CONCLUSIONS

The fennel EO can thus be formulated as a plant-based preservative for food items.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present investigation comprises the first report on antiaflatoxin efficacy of fennel oil and its potency in the protection of tobacco leaves from fungal and aflatoxin contamination during storage.