Impact of Cymbopogon flexuosus (Poaceae) essential oil and primary components on the eclosion and larval development of Aedes aegypti

The current study describes the effects of sub-lethal concentrations and constituent compounds (citral and geranyl acetate) of Cymbopogon flexuosus essential oil (EO) on the development of Aedes aegypti. We treated eggs with 6, 18, or 30 mg L−1 and larvae with 3 or 6 mg L−1 of EO and its major compounds (citral and geranyl acetate). Citral and geranyl acetate were evaluated at 18, 30, and 42 mg L−1 and compared with commercial growth inhibitors (diflubenzuron and methoprene). We measured larval head diameter, siphon length, and larval length. Finally, we examined concentrations of molt hormone (MH) and juvenile hormone III (JH III) using high-performance liquid chromatography coupled to mass spectrometry. All geranyl acetate concentrations decreased egg hatching, while EO altered molting among larval instars and between larvae and pupae, with an increase in the larval length (3 mg L−1: 6 ± 0.0 mm; 6 mg L−1: 6 ± 0.7 mm) and head width (3 mg L−1: 0.8 ± 0 mm; 6 mg L−1: 0.8 ± 0.0 mm) compared with the control group. We did not detect chromatographic signals of MH and JH III in larvae treated with C. flexuosus EO or their major compounds. The sub-lethal concentrations C. flexuosus EO caused a similar effect to diflubenzuron, namely decreased hormone concentrations, an extended larval period, and death.

Physical localization of 45S rDNA in Cymbopogon and the analysis of differential distribution of rDNA in homologous chromosomes of Cymbopogon winterianus

Cymbopogon, commonly known as lemon grass, is one of the most important aromatic grasses having therapeutic and medicinal values. FISH signals on somatic chromosome spreads off Cymbopogon species indicated the localization of 45S rDNA on the terminal region of short arms of a chromosome pair. A considerable interspecific variation in the intensity of 45S rDNA hybridization signals was observed in the cultivars of Cymbopogon winterianus and Cymbopogon flexuosus. Furthermore, in all the varieties of C. winterianus namely Bio-13, Manjari and Medini, a differential distribution of 45S rDNA was observed in a heterologous pair of chromosomes 1. The development of C. winterianus var. Manjari through gamma radiation may be responsible for breakage of fragile rDNA site from one of the chromosomes of this heterologous chromosome pair. While, in other two varieties of C. winterianus (Bio-13 and Medini), this variability may be because of evolutionary speciation due to natural cross among two species of Cymbopogon which was fixed through clonal propagation. However, in both the situations these changes were fixed by vegetative method of propagation which is general mode of reproduction in the case of C. winterianus.

ANTIMICROBIAL PROPERTIES OF RABBIT COLLAGEN GLUE-CHITOSAN BIOMATERIAL LOADED WITH CYMBOPOGON FLEXUOSUS ESSENTIAL OIL

One approach to develop innovative antimicrobial wound dressing materials is to use natural polymers loaded with antimicrobial agents. The valorisation of animal proteins as biomaterials with antimicrobial properties is a new concern for development of wound healing. Plant esssential oils (EO) also indicate a potential approach for new wound dressing materials able to replace the synthetic antymicrobial agents. In this paper, plant-polymeric film was prepared by casting film-forming emulsion based on lemongrass (Cymbopogon flexuosus) essential oil/Tween 80 dispersed into rabbit collagen glue hydrolysate– chitosan biomaterial. The effect of biomaterial film composition on Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 10536 standard bacteria, and Candida albicans ATCC 10231 pathogenic fungus was studied according to European Pharmacopoeia 10/2020 as compared with biomaterial film without essential oil. The in vitro antibacterial tests against three bacterial strains showed that the rabbit collagen glue hydrolysate–chitosan biomaterial inhibited all the three microorganisms. The rabbit collagen hydrolysate glue-chitosan film loaded with lemongrass essential oil exhibits antimicrobial activity towards tested microorganisms but lower as compared with control. The explanation could be due to the short time of investigation, or maybe some active compounds constituents of EO, which favour the cellular proliferation. Preparation of rabbit collagen glue hydrolysate-chitosan biomaterial loaded with lemongrass essential oil is an environmentally friendly solution, which may contribute to the development of wound healing materials as an alternative to topical antimicrobial agents.

Control of Aspergillus flavus in wheat grains using Cymbopogon flexuosus essential oil

Fungi are one of the main food spoilage agents. Numerous species when subjected to stress conditions produce secondary metabolites known as mycotoxins, which are mutagenic and carcinogenic substances. The fungus Aspergillus flavus is one of the main contaminants of grains and is known to produce Aflatoxin. Pesticides are used in agriculture to contain fungi and other pests, but they harm other species, the environment and the human health, in addition to the development of resistance to these substances in pest species. Natural alternatives have been sought to control these organisms. In this context, essential oils are a viable option against A. flavus. The aim of this study was to identify the main components and evaluate the effectiveness of lemongrass essential oil (Cymbopogon flexuosus) for controlling the fungus Aspergillus flavus. Initially, the effect of essential oil on mycelial growth of the fungus was assessed by in vitro tests at the doses: 0.05; 0.1; 0.2; 0.4; 0.6; 0.8; 1.6; 3.2; 6.4; and 12.8 μL mL-1. The minimum inhibitory concentration (MIC) was 0.8 μL mL-1. The in vivo test was performed at the following concentrations: 0.6; 0.8; and 1.6 μL mL-1. The results showed that the essential oil has fungicidal potential against A. flavus. The main component of the essential oil was citral.

Effects of Organic Manures and Green Manuring on Growth, Yield, Economics and Quality of Lemongrass (Cymbopogon Flexuosus L.) In Custard Apple (Annona Squamosa L.) Based Agri-Horti System

A field experiment was conducted to explore the effects of organic manures and green manuring practices on growth, yield attributes, quality and economics of lemongrass (Cymbopogon flexuosus L.) under custard apple (Annona squamosa L.) based agri-horti system. The findings indicated that growth, yield attributes and yield as well as oil composition, soil nutrient status, microbial populations were significantly increased due to the use of both organic manures and green manuring. The significantly higher results were obtained with vermicompost (2.5 t/ha) + Azotobacter, which was found superior over other practices in terms of growth, yield attributes, oil composition and its quality and soil nutrient status as well as economics of crop cultivation. Bangladesh J. Bot. 50(3): 499-506, 2021 (September)

Augmenting the Activity of Chlorhexidine for Decolonization of Candida auris from Porcine skin

Candida auris readily colonizes skin and efficiently spreads among patients in healthcare settings worldwide. Given the capacity of this drug-resistant fungal pathogen to cause invasive disease with high mortality, hospitals frequently employ chlorhexidine bathing to reduce skin colonization. Using an ex vivo skin model, we show only a mild reduction in C. auris following chlorhexidine application. This finding helps explain why chlorhexidine bathing may have failures clinically, despite potent in vitro activity. We further show that isopropanol augments the activity of chlorhexidine against C. auris on skin. Additionally, we find both tea tree (Melaleuca alternifolia) oil and lemongrass (Cymbopogon flexuosus) oil to further enhance the activity of chlorhexidine/isopropanol for decolonization. We link this antifungal activity to individual oil components and show how some of these components act synergistically with chlorhexidine/isopropanol. Together, the studies provide strategies to improve C. auris skin decolonization through the incorporation of commonly used topical compounds.