Bacillus megaterium: Evaluation of Chemical Nature of Metabolites and Their Antioxidant and Agronomics Properties.

Bacillus megaterium is particularly known for its abundance in soils and its plant growth promotion. To characterize the metabolites excreted by this specie, we performed successive liquid/liquid extractions from bacteria culture medium with different polarity solvents (cyclohexane, dichloromethane, ethyl acetate and butanol) to separate the metabolites in different polarity groups. The extracts were characterized regarding their total phenolic content, the amount of reducing sugar, the concentration of primary amines and proteins, their chromatographic profile by HPLC-DAD-ELSD and their chemical identification by GC-MS. Among the 75 compounds which are produced by the bacteria, 19 identifications were for the first time found as metabolites of B. megaterium and 23 were described for the first time as metabolites in Bacillus genus. The different extracts containing B. megaterium metabolites showed interesting agronomic activity, with a global inhibition of seed germination rates of soya, sunflower, corn and ray grass, but not of corn, compared to culture medium alone. Our results suggest that B. megaterium can produce various metabolites, like butanediol, cyclic dipeptides, fatty acids, and hydrocarbons, with diverse effects and sometimes with opposite effects in order to modulate its response to plant growth and adapt to various environmental effects. These findings provide new insight into bioactive properties of this species for therapeutic uses on plants.

Management of Plant Beneficial Fungal Endophytes to Improve the Performance of Agroecological Practices.

By dint of the development of agroecological practices and organic farming, stakeholders are becoming more and more aware of the importance of soil life and banning a growing number of pesticide molecules, promoting the use of plant bio-stimulants. To justify and promote the use of microbes in agroecological practices and sustainable agriculture, a number of functions or services often are invoked: (i) soil health, (ii) plant growth promotion, (iii) biocontrol, (iv) nutrient acquiring, (v) soil carbon storage, etc. In this paper, a review and a hierarchical classification of plant fungal partners according to their ecosystemic potential with regard to the available technologies aiming at field uses will be discussed with a particular focus on interactive microbial associations and functions such as Mycorrhiza Helper Bacteria (MHB) and nurse plants.

Plant antimicrobial polyphenols as potential natural food preservatives.

BACKGROUND: The growing demand for natural food preservatives in the last decade has promoted investigations on their application for preserving perishable foods. In this context, the present review is focused on discussing the prospective application of plant extracts containing phenolics or isolated plant phenolics as natural antimicrobials in foods. Plant essential oils are outside the scope of this review since utilization of their antimicrobial activity for food preservation has been extensively reviewed. RESULTS: Although the exact antimicrobial mechanisms of action of phenolic compounds are not yet fully understood, it is commonly acknowledged that they have diverse sites of action at the cellular level. Antimicrobial phenolics can be added directly to the formulation of perishable food products or incorporated into food-contact materials to release them in the immediate zone of perishable foods. Edible coatings or active food packaging materials can thus be used as carriers of plant bioactive compounds. CONCLUSION: These materials could be an interesting delivery system to improve the stability of phenolics in foods and to improve the shelf life of perishable foods. This review will thus provide an overview of current knowledge of the antimicrobial activity of phenolic-rich plant extracts and of the promises and limits of their exploitation for the preservation of perishable foods. © 2018 Society of Chemical Industry.

Synthesis of New Arylidene 2,5-Diketopiperazines and Evaluation of their Anti-Acetylcholinesterase, Anti-xanthine Oxidase, Anti-diabetic and Cytotoxic Activities.

BACKGROUND: 2,5-Diketopiperazine derivatives are considered to be an important classe of cyclic peptides due to their wide range of biological activities. OBJECTIVES: Synthesis of a new series of protected 2,5-diketopiperazine derivatives and evaluation of their in vitro biological activities. METHODS: A series of new mono-protected arylidene 2,5-diketopiperazine derivatives 3a-p have been prepared via Claisen-Schmidt condensation of the N,N-diacetyl-diketopiperazine 1 with a series of substituted arylaldehydes. All prepared compounds were characterized by 1D and 2D 1H/13C NMR and ESI-HRMS, and screened for their in vitro acetylcholenesterase, xanthine oxidase and α-amylase inhibition and cytotoxic (HCT-116, MCF-7 and OVCAR-3) activity. RESULTS: Among these compounds, the greatest activity against the α-amylase enzyme (percentage of inhibition (PI)=57.8±1.9%) was obtained for compound 3f bearing a phenoxy moiety. Moreover, the results demonstrated that some arylidene 2,5-diketopiperazines 3 exhibited significant cytotoxic activity against the three cell lines used. The compound 3g (4-PhCH2O.Ph) was found to be the most cytotoxic against the HCT-116, MCF-7 and OVCAR-3 cell lines (PI=83.2±2.4, 89.6±4.9 and 74.4±5.2%, respectively) followed by 3m (2-Br-5-F.Ph) then 3j (4-C2H5-3-NO2.Ph) which displayed a good cytotoxic potential against OVCAR-3 (PI=77.0±2.1 and 71.4±0.9%, respectively). CONCLUSION: A series of sixteen new arylidene diketopiperazines 3a-p were synthesized via Claisen-Schmidt condensation. Most of the piperazines 3a-p exhibited a good cytotoxic and antidiabetic effects.

Antioxidant activity and hepatoprotective potential of Cedrelopsis grevei on cypermethrin induced oxidative stress and liver damage in male mice.

BACKGROUND: The liver is the most sensitive and main target organ of pesticide toxicity and damage, they play an essential role in metabolism and detoxification of pesticides. Due to these functions, hepatotoxicity continues to be among the main threats to public health, and they remain problems throughout the world. Therefore, the present study was designed to evaluate the antioxidant and hepatoprotective effects of Cedrelopsis grevei leaves against cypermethrin (Cyp) induced oxidative stress and liver damage in male mice. METHODS: The extracts were subjected to different analyses (phenolics, tannin, flavonoids, antioxidant activity and reducing power assays). For hepatoprotective evaluation, male mice were daily exposed to Cyp and/or C. grevei by gavages for 28 days. Hepatoprotective effects were demonstrated by significant alterations in serum liver dysfunction biomarker enzymes, liver lipid peroxidation and antioxidant enzymes. RESULTS: The antioxidant activity of C. grevei methanolic extract was the highest with an IC50<225 µg/ml by DPPH assay. The high dose of methanolic extract (300 mg/kg. b.wt.) was effective to attenuate the perturbations in the tested enzymes. Histopathological examination in the liver tissue of those mice, demonstrated that a co-administration of methanolic extract (150 & 300 mg/kg/day) showed marked improvement in its histological structure in comparison to Cyp-treated group alone and represented by nil to moderate degree in inflammatory cells. CONCLUSIONS: In view of the data of the present study, it can deduce that cypermethrin caused oxidative damage and liver dysfunction in male mice. C. grevei extract has protective effects on cypermethrin-induced lipid peroxidation, oxidative stress and liver damage. Results indicated that administration of C. grevei is useful, easy, and economical to protect humans against pesticide toxicity. The results presented here can be considered as the first information on the hepatoprotective and antioxidant properties of C. grevei extracts. In a future study, we will identify and investigate the components responsible for the hepatoprotective and antioxidant activities of C. grevei.

Foliar treatments with Gaultheria procumbens essential oil induce defense responses and resistance against a fungal pathogen in Arabidopsis.

Essential oil from Gaultheria procumbens is mainly composed of methylsalicylate (MeSA) (>96%), a compound which can be metabolized in plant tissues to salicylic acid, a phytohormone inducing plant immunity against microbial pathogens. The potential use of G. procumbens essential oil as a biocontrol agent was evaluated on the model plant Arabidopsis thaliana. Expression of a selection of defense genes was detected 1, 6, and 24 h after essential oil treatment (0.1 ml/L) using a high-throughput qPCR-based microfluidic technology. Control treatments included methyl jasmonate and a commercialized salicylic acid (SA) analog, benzo(1,2,3)-thiadiazole-7carbothiolic acid (BTH). Strong induction of defense markers known to be regulated by the SA pathway was observed after the treatment with G. procumbens essential oil. Treatment induced the accumulation of total SA in the wild-type Arabidopsis line Col-0 and analysis of the Arabidopsis line sid2, mutated in a SA biosynthetic gene, revealed that approximately 30% of MeSA sprayed on the leaves penetrated inside plant tissues and was demethylated by endogenous esterases. Induction of plant resistance by G. procumbens essential oil was tested following inoculation with a GFP-expressing strain of the Arabidopsis fungal pathogen Colletotrichum higginsianum. Fluorescence measurement of infected tissues revealed that treatments led to a strong reduction (60%) of pathogen development and that the efficacy of the G. procumbens essential oil was similar to the commercial product BION(®). Together, these results show that the G. procubens essential oil is a natural source of MeSA which can be formulated to develop new biocontrol products.

Chemical composition and anticancer, antiinflammatory, antioxidant and antimalarial activities of leaves essential oil of Cedrelopsis grevei.

The essential oil from Cedrelopsis grevei leaves, an aromatic and medicinal plant from Madagascar, is widely used in folk medicine. Essential oil was characterized by GC-MS and quantified by GC-FID. Sixty-four components were identified. The major constituents were: (E)-ß-farnesene (27.61%), δ-cadinene (14.48%), α-copaene (7.65%) and ß-elemene (6.96%). The essential oil contained a complex mixture consisting mainly sesquiterpene hydrocarbons (83.42%) and generally sesquiterpenes (98.91%). The essential oil was tested cytotoxic (on human breast cancer cells MCF-7), antimalarial (Plasmodium falciparum), antiinflammatory and antioxidant (ABTS and DPPH assays) activities. C. grevei essential oil was active against MCF-7 cell lines (IC50=21.5 mg/L), against P. falciparum, (IC50=17.5mg/L) and antiinflammatory (IC50=21.33 mg/L). The essential oil exhibited poor antioxidant activity against DPPH (IC50>1000 mg/L) and ABTS (IC50=110 mg/L) assays. A bibliographical review was carried out of all essential oils identified and tested with respect to antiplasmodial, anticancer and antiinflammatory activities. The aim was to establish correlations between the identified compounds and their biological activities (antiplasmodial, anticancer and antiinflammatory). According to the obtained correlations, 1,4-cadinadiene (R(2)=0.61) presented a higher relationship with antimalarial activity. However, only (Z)-ß-farnesene (R(2)=0.73) showed a significant correlation for anticancer activity.

Helichrysum gymnocephalum essential oil: chemical composition and cytotoxic, antimalarial and antioxidant activities, attribution of the activity origin by correlations.

Helichrysum gymnocephalum essential oil (EO) was prepared by hydrodistillation of its leaves and characterized by GC-MS and quantified by GC-FID. Twenty three compounds were identified. 1,8-Cineole (47.4%), bicyclosesquiphellandrene (5.6%), γ-curcumene (5.6%), α-amorphene (5.1%) and bicyclogermacrene (5%) were the main components. Our results confirmed the important chemical variability of H. gymnocephalum. The essential oil was tested in vitro for cytotoxic (on human breast cancer cells MCF-7), antimalarial (Plasmodium falciparum: FcB1-Columbia strain, chloroquine-resistant) and antioxidant (ABTS and DPPH assays) activities. H. gymnocephalum EO was found to be active against MCF-7 cells, with an IC(50) of 16 ± 2 mg/L. The essential oil was active against P. falciparum (IC(50) = 25 ± 1 mg/L). However, the essential oil exhibited a poor antioxidant activity in the DPPH (IC(50) value > 1,000 mg/L) and ABTS (IC(50) value = 1,487.67 ± 47.70 mg/L) assays. We have reviewed the existing results on the anticancer activity of essential oils on MCF-7 cell line and on their antiplasmodial activity against the P. falciparum. The aim was to establish correlations between the identified compounds and their biological activities (antiplasmodial and anticancer). ß-Selinene (R² = 0.76), α-terpinolene (R² = 0.88) and aromadendrene (R² = 0.90) presented a higher relationship with the anti-cancer activity. However, only calamenene (R² = 0.70) showed a significant correlation for the antiplasmodial activity.