Inhibition of chitin synthases and antifungal activities by 2'-benzoyloxycinnamaldehyde from Pleuropterus ciliinervis and its derivatives

Plant-Derived Pesticides as an Alternative to Pest Management and Sustainable Agricultural Production: Prospects, Applications and Challenges

Pests and diseases are responsible for most of the losses related to agricultural crops, either in the field or in storage. Moreover, due to indiscriminate use of synthetic pesticides over the years, several issues have come along, such as pest resistance and contamination of important planet sources, such as water, air and soil. Therefore, in order to improve efficiency of crop production and reduce food crisis in a sustainable manner, while preserving consumer's health, plant-derived pesticides may be a green alternative to synthetic ones. They are cheap, biodegradable, ecofriendly and act by several mechanisms of action in a more specific way, suggesting that they are less of a hazard to humans and the environment. Natural plant products with bioactivity toward insects include several classes of molecules, for example: terpenes, flavonoids, alkaloids, polyphenols, cyanogenic glucosides, quinones, amides, aldehydes, thiophenes, amino acids, saccharides and polyketides (which is not an exhaustive list of insecticidal substances). In general, those compounds have important ecological activities in nature, such as: antifeedant, attractant, nematicide, fungicide, repellent, insecticide, insect growth regulator and allelopathic agents, acting as a promising source for novel pest control agents or biopesticides. However, several factors appear to limit their commercialization. In this critical review, a compilation of plant-derived metabolites, along with their corresponding toxicology and mechanisms of action, will be approached, as well as the different strategies developed in order to meet the required commercial standards through more efficient methods.

Involvement of a Multidrug Efflux Pump and Alterations in Cell Surface Structure in the Synergistic Antifungal Activity of Nagilactone E and Anethole against Budding Yeast Saccharomyces cerevisiae

Nagilactone E, an antifungal agent derived from the root bark of Podocarpus nagi, inhibits 1,3-β glucan synthesis; however, its inhibitory activity is weak. Anethole, the principal component of anise oil, enhances the antifungal activity of nagilactone E. We aimed to determine the combinatorial effect and underlying mechanisms of action of nagilactone E and anethole against the budding yeast Saccharomyces cerevisiae. Analyses using gene-deficient strains showed that the multidrug efflux pump PDR5 is associated with nagilactone E resistance; its transcription was gradually restricted in cells treated with the drug combination for a prolonged duration but not in nagilactone-E-treated cells. Green-fluorescent-protein-tagged Pdr5p was intensively expressed and localized on the plasma membrane of nagilactone-E-treated cells but not in drug-combination-treated cells. Quick-freeze deep-etch electron microscopy revealed the smoothening of intertwined fiber structures on the cell surface of drug-combination-treated cells and spheroplasts, indicating a decline in cell wall components and loss of cell wall strength. Anethole enhanced the antifungal activity of nagilactone E by enabling its retention within cells, thereby accelerating cell wall damage. The combination of nagilactone E and anethole can be employed in clinical settings as an antifungal, as well as a food preservative to restrict food spoilage.

Synthesis and Antifungal Activities of Cinnamaldehyde Derivatives against Penicillium digitatum Causing Citrus Green Mold

Penicillium digitatum (green mold) is pathogenic fungi and causes citrus fruit postharvest rotting that leads to huge economic losses across the world. The current study was aimed to develop a new derivative of cinnamaldehyde (4-methoxycinnamaldehyde) through the cross-hydroxyaldehyde condensation method with benzaldehyde substituted by a benzene ring under the catalysis of alkaline reagent and, moreover, to test their antifungal potential against P. digitatum, the major citrus fruit rotting fungi. Multiple derivatives of cinnamaldehyde viz. 4-nitro CA, 4-chloro CA, 4-bromo CA, 4-methyl CA, 4-methoxy CA, and 2,4-dimethoxy CA were synthesized in the current study whereas the 4-methoxy CA showed highest antifungal actions for citrus fruit postharvest rotting fungi P. digitatum. Moreover, 4-methoxy CA was found to reduce the spore germination and growth by damaging the fungal cell membrane, as well as declined the levels of reducing sugars.

In vitro assessment of antimicrobial activity of aqueous and alcoholic extracts of moss Atrichum undulatum (Hedw.) P. Beauv

Bryophytes, the shade loving plants, have tremendous medicinal properties. The aqueous and alcoholic extracts of Atrichum undulatum (Hedw.) P. Beauv. were analysed for antimicrobial properties against the fungi Aspergillus fumigatus and Fusarium oxysporum and the bacteria Escherichia coli, Bacillus mycoides, Proteus mirabilis, Staphylococcus aureus and Salmonella typhi. The study is an attempt to investigate the medicinal properties of Atrichum undulatum (Hedw.) P. Beauv. using disc-diffusion method. No inhibition was observed against A. fumigatus and P. mirabilis. For bacteria S. typhi and E. coli (20 and 15 mm), aqueous and alcoholic extracts of Atrichum showed significant inhibition. However, alcoholic extract was found remarkably effective against bacteria rather than aqueous extract.

Cinnamaldehyde and its derivatives, a novel class of antifungal agents

The last few decades have seen an alarming rise in fungal infections, which currently represent a global health threat. Despite extensive research towards the development of new antifungal agents, only a limited number of antifungal drugs are available in the market. The routinely used polyene agents and many azole antifungals are associated with some common side effects such as severe hepatotoxicity and nephrotoxicity. Also, antifungal resistance continues to grow and evolve and complicate patient management, despite the introduction of new antifungal agents. This suitation requires continuous attention. Cinnamaldehyde has been reported to inhibit bacteria, yeasts, and filamentous molds via the inhibition of ATPases, cell wall biosynthesis, and alteration of membrane structure and integrity. In this regard, several novel cinnamaldehyde derivatives were synthesized with the claim of potential antifungal activities. The present article describes antifungal properties of cinnamaldehyde and its derivatives against diverse classes of pathogenic fungi. This review will provide an overview of what is currently known about the primary mode of action of cinnamaldehyde. Synergistic approaches for boosting the effectiveness of cinnamaldehyde and its derivatives have been highlighted. Also, a keen analysis of the pharmacologically active systems derived from cinnamaldehyde has been discussed. Finally, efforts were made to outline the future perspectives of cinnamaldehyde-based antifungal agents. The purpose of this review is to provide an overview of current knowledge about the antifungal properties and antifungal mode of action of cinnamaldehyde and its derivatives and to identify research avenues that can facilitate implementation of cinnamaldehyde as a natural antifungal.

Natural toxins for use in pest management

Natural toxins are a source of new chemical classes of pesticides, as well as environmentally and toxicologically safer molecules than many of the currently used pesticides. Furthermore, they often have molecular target sites that are not exploited by currently marketed pesticides. There are highly successful products based on natural compounds in the major pesticide classes. These include the herbicide glufosinate (synthetic phosphinothricin), the spinosad insecticides, and the strobilurin fungicides. These and other examples of currently marketed natural product-based pesticides, as well as natural toxins that show promise as pesticides from our own research are discussed.

Transport and metabolism of the antitumour drug candidate 2'-benzoyloxycinnamaldehyde in Caco-2 cells

The transport and metabolism of the antitumour drug candidate 2'-benzoyloxycinnamaldehyde (BCA) was characterized in Caco-2 cells. BCA disappeared rapidly from the donor side without being transported to the receiver side during its absorptive transport across Caco-2 cells. Its metabolites 2'-hydroxycinnamaldehyde (HCA) and o-coumaric acid (OCA) were formed in both the donor and the receiver sides. HCA, in a separate study, also disappeared rapidly from the donor side, mostly being converted to its oxidative metabolite OCA during its absorptive transport across Caco-2 cells. OCA was transported rapidly in the absorptive direction across Caco-2 cells with a P(app) of 25.4 +/- 1.0 x 10(-6) cm s(-1) (mean +/- standard deviation (SD), n = 3). OCA was fully recovered from both the donor and the receiver side throughout the time-course of this study. Formation of HCA from BCA was inhibited almost completely by bis(p-nitrophenyl)phosphate (BNPP), a selective inhibitor of carboxylesterases (CES), and phenylmethylsulfonyl fluoride (PMSF), a broad specificity inhibitor of esterases in Caco-2 cells, suggesting that this hydrolytic biotransformation was likely mediated predominantly by CES. Conversion of HCA to OCA was inhibited significantly by isovanillin, a selective inhibitor of aldehyde oxidase (AO). Inhibitors for xanthine oxidase (XO) and aldehyde dehydrogenase (ALDH), which are known to be involved in the oxidation of aldehydes to carboxylic acids, did not have a significant effect on the biotransformation of HCA to OCA in Caco-2 cells. In summary, the present work demonstrates that BCA is hydrolysed rapidly to HCA, followed by subsequent oxidation to OCA, in Caco-2 cells. The results provide a mechanistic understanding of the poor absorption and low bioavailability of BCA after oral administration.

2'-Benzoyloxycinnamaldehyde inhibits tumor growth in H-ras12V transgenic mice via downregulation of metallothionein

Cinnamaldehydes have been reported to induce apoptosis in human carcinomas through the generation of reactive oxygen species (ROS). 2'-benzoyloxycinnamaldehyde (BCA) has been reported to inhibit tumor formation in H-ras12V transgenic mice. To see the antitumor effects of BCA, BCA was administrated intraperitoneally (50 mg/kg) to H-ras12V transgenic mice for 3 wk, and it was found that the hepatic tumor volume and the total number of tumors were decreased in BCA-treated mice as compared to control H-ras12V transgenic mice. To identify possible target genes responsible for BCA antitumor effects in H-ras12V transgenic mice, cDNA microarray analyses were performed comparing gene expression between BCA treated and control transgenic mice. We found that 42 genes were downregulated, and 40 genes were upregulated in the BCA-treated transgenic mice. The downregulated genes included several genes involved in ROS regulation and immune response (aconitase, metallothionein-1, metallothionein-2, and purine nucleoside phosphorylase). The expression of ROS-related genes, metallothionein 1 and metallothionein 2, was decreased more than twofold with BCA treatment (P < 0.001). It was confirmed by RT-PCR and immunohistochemical analyses. The inhibition of tumor formation and growth in H-ras12V transgenic mice by BCA was mediated through inhibition of the expression of the ROS scavengers metallothionein 1 and metallothionein 2.

Plasma pharmacokinetics and metabolism of the antitumour drug candidate 2'-benzoyloxycinnamaldehyde in rats

The pharmacokinetics and metabolism of 2'-benzoyloxycinnamaldehyde (BCA) was characterized in male Sprague-Dawley rats as part of the preclinical evaluations for developing this compound as an antitumour agent. BCA was not detected in the plasma following either intravenous or oral dose, whereas its putative metabolites 2'-hydroxycinnamaldehyde (HCA) and o-coumaric acid were present at considerable levels. In separate pharmacokinetics studies, HCA exhibited a high systemic clearance and a large volume of distribution, whereas both pharmacokinetic parameters were much lower for o-coumaric acid. The terminal half-life of both metabolites was approximately 2 h. BCA was converted rapidly to HCA in rat serum, liver microsomes and cytosol in vitro; HCA was subsequently converted to o-coumaric acid in a quantitative manner only in the liver cytosol. In addition, the formation of o-coumaric acid was inhibited significantly by menadione, a specific inhibitor for aldehyde oxidase. Taken collectively, the results suggest that the rapid systemic clearance of HCA is likely due mainly to hepatic clearance occurring from aldehyde oxidase-catalysed biotransformation to o- coumaric acid. In conclusion, the present work demonstrates that the anticancer drug candidate BCA is highly likely to work as its active metabolite HCA in the body.

Natural products in crop protection

The tremendous increase in crop yields associated with the 'green' revolution has been possible in part by the discovery and utilization of chemicals for pest control. However, concerns over the potential impact of pesticides on human health and the environment has led to the introduction of new pesticide registration procedures, such as the Food Quality Protection Act in the United States. These new regulations have reduced the number of synthetic pesticides available in agriculture. Therefore, the current paradigm of relying almost exclusively on chemicals for pest control may need to be reconsidered. New pesticides, including natural product-based pesticides are being discovered and developed to replace the compounds lost due to the new registration requirements. This review covers the historical use of natural products in agricultural practices, the impact of natural products on the development of new pesticides, and the future prospects for natural products-based pest management.