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As part of the development of alternative and environmentally friendly control against phytopathogenic fungi, Burkholderia cepacia could be a useful species notably via the generation of hydrolytic enzymes like chitinases, which can act as a biological control agent. Here, a Burkholderia contaminans S614 strain exhibiting chitinase activity was isolated from a soil in southern Tunisia. Then, response surface methodology (RSM) with a central composite design (CCD) was used to assess the impact of five factors (colloidal chitin, magnesium sulfate, dipotassium phosphate, yeast extract, and ammonium sulfate) on chitinase activity. B. contaminans strain 614 growing in the optimized medium showed up to a 3-fold higher chitinase activity. This enzyme was identified as beta-N-acetylhexosaminidase (90.1 kDa) based on its peptide sequences, which showed high similarity to those of Burkholderia lata strain 383. Furthermore, this chitinase significantly inhibited the growth of two phytopathogenic fungi: Botrytis cinerea M5 and Phoma medicaginis Ph8. Interestingly, a crude enzyme from strain S614 was effective in reducing P. medicaginis damage on detached leaves of Medicago truncatula. Overall, our data provide strong arguments for the agricultural and biotechnological potential of strain S614 in the context of developing biocontrol approaches. [ABSTRACT FROM AUTHOR]

Combination therapy at appropriately suitable doses presents a promising alternative to monotherapeutic drugs. In this study, Cinnamomum verum and Syzygium aromaticum essential oils and their major compounds have exhibited substantial leishmaniacidal potential against both promastigote and amastigote forms of Leishmania (L.) major. However, they displayed high cytotoxicity against Raw264.7 macrophage cells. Interestingly, when combined with each other or with amphotericin B, they demonstrated a synergistic effect (FIC<0.5) with low cytotoxicity. These combinations are able to modulate the production of nitric oxide (NO) by macrophages. Notably, the combination of S. aromaticum Essential oil with amphotericin B stimulates macrophage cells by increasing NO production to eliminate leishmanial parasites. Furthermore, investigation of the molecular mechanism of action of these synergistic combinations reveals potent inhibition of the sterol pathway through the inhibition of the CYP51 gene expression. The findings suggest that combination therapy may offer significant therapeutic benefits in both food and pharmaceutical fields. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the leishmanicidal potential of the essential oil (EO) of Micromeria (M.) nervosa and to investigate its molecular mechanism of action by qPCR. Furthermore, in silicointeraction study of the major M. nervosa EO compounds with the enzyme cytochrome P450 sterol 14α-demethylase (CYP51) was also performed. M. nervosa EO was analyzed by gas chromatography-mass spectrometry (GC-MS). Results showed that α-pinene (26.44%), t-cadinol (26.27%), caryophyllene Oxide (7.73 ± 1.04%), and α-Cadinene (3.79 ± 0.12%) are the major compounds of M. nervosa EO. However, limited antioxidant activity was observed, as this EO was ineffective in neutralizing DPPH free radicals and in inhibiting β-carotene bleaching. Interestingly, it displayed effective leishmanicidal potential against promastigote (IC50 of 6.79 and 5.25 μg/mL) and amastigote (IC50 of 8.04 and 7.32 μg/mL) forms of leishmania (L.) infantum and L. major, respectively. Molecular mechanism investigation showed that M. nervosa EO displayed potent inhibition on the thiol regulatory pathway. Furthermore, a docking study of the main components of the EO with cytochrome P450 sterol 14α-demethylase (CYP51) enzyme revealed that t-cadinol exhibited the best binding energy values (−7.5 kcal/mol), followed by α-cadinene (−7.3 kcal/mol) and caryophyllene oxide (−7 kcal/mol). These values were notably higher than that of the conventional drug fluconazole showing weaker binding energy (−6.9 kcal/mol). These results suggest that M. nervosa EO could serve as a potent and promising candidate for the development of alternative antileishmanial agent in the treatment of leishmaniasis. [ABSTRACT FROM AUTHOR]

The antifungal activity of volatile organic compounds (VOCs) from 10 Streptomyces isolates was tested using the double-dish chamber method. The VOCs-producing strain S97 exhibited the highest inhibitory effect against Botrytis cinerea mycelium growth. This isolate was identified as Streptomyces sp. with high similarity with Streptomyces lydicus based on morphological and physiological properties, as well as 16S rRNA gene sequence analysis. S97 VOCs analysis was performed by SPME–GC–MS revealing the presence of 14 compounds including three major terpenoids: 3-carene 2,5-dione, geosmin, beta-cubebene and one phenolic compound Phenol, 2-(1,1-dimethylethyl)-6-methyl- representing 43%, 20%, 11% and 9.34% of total produced VOCs, respectively. S97 VOCs inhibited mycelial growth of Rhizoctonia solani and Phoma medicaginis by 95%, Fusarium solani by 69% and Fusarium oxysporum and Sclerotium rolfsii by 20%. The in vivo test carried out on ripe strawberries inoculated by Botrytis cinerea conidia showed that S97 VOCs inhibited the development of grey mould symptoms on fruits by more than 87% compared to untreated control strawberries. Further, light microscope observations revealed 60% swelling and 21% crumbling of B. cinerea conidia when treated with S97 VOCs. Fungal mycelium also showed deep structural alterations with S97 VOCs after 48 h incubation. Strain S97 exhibited strong fumigation potential to control phytopathogenic fungi. [ABSTRACT FROM AUTHOR]

A new heterogeneous acid catalyst based on a natural resource, Tunisian clay (Clay-H0.5), has been prepared and characterized by FT-IR, FE-SEM, and powder X-ray diffraction (XRD), as well as chemical composition, cation exchange capacity, specific surface area, and pore volume. Acid treatment for 0.5 h enlarged the surface area from 78.24 to 186.10 m²/g and pore volume (PV) from 0.186 to 0.281 cm³/g. The catalytic activity of this material was investigated in ketalization reaction under mild solvent-free conditions. This achieved up to 92% isolated yield for only 10 wt.% of the catalyst. This environmentally friendly method has advantages such as simple work-up procedure, avoidance of organic solvents, and good performance in ketalization reactions. Importantly, the Clay-H0.5 catalyst showed good recyclability where insignificant activity loss was exhibited even after six runs. Synthesized cyclic ketals were tested for their possible antileishmanial and antibacterial activities as well as antifungal activity. Biological screening showed that compound 11 had important antileishmanial activity against both L. major and L. infantum, while compound 14 also had significant antibacterial activity against four gram-positive and two gram-negative bacteria, and antifungal activity against Candida albicans, with minimal inhibitory concentration values ranging from 15.62 μg/mL to 125 μg/mL. [ABSTRACT FROM AUTHOR]