Methoxy Chalcone Derivatives: Promising Antimicrobial Agents Against Phytopathogens.

Chalcone (E)-1,3-diphenyl-prop-2-en-1-one and a series of 14 methoxylated derivatives have been synthesized via Claisen-Schmidt aldol condensation and characterized by FTIR, CG/MS/DIC, 1D (1H and 13C), 2D (COSY, HSQC, and HMBC) NMR, and EMAR techniques. All molecules were tested at 1 mM concentration for antifungal (Sclerotium sp., Macrophomina phaesolina and Colletotrichum gloeosporioides), antibacterial (Acidovorax citrulli two strains), and antiprotozoal (Phytomonas serpens) activities. Unmodified chalcone (CH0) and derivatives CH1, CH2, CH8 stood out in terms of antifungal activity. CH0 presented IC50 values of 47.3 µM (9.8 µg/mL) for the fungus C. gloeosporioides. In addition, fluorescence microscopy indicated that CH0 promoted loss of hyphal cell membrane integrity. The CH1 and CH2 derivatives promoted the inhibition of Sclerotium sp. with IC50 of 127.5 µM (32.9 µg/mL) and 110.4 µM (29.6 µg/mL), respectively. All molecules showed high activity against the phytoparasite P. serpens with IC50 values of 0.98, 2.40, 10.25, and 3.11 µM for the derivatives CH2, CH3, CH5 and CH14 respectively. The results demonstrated that derivatives methoxylated in both rings (CH2) as well as derivatives with a furan ring associated with the methoxy group in ring A, as well as unmodified chalcone can be promising agricultural fungicides for controlling the fungi studied.

Exploring the Exo-Metabolomes and Volatile and Non-Volatile Compounds of Metarhizium carneum and Lecanicillium uredinophilum.

Efforts are intensifying to identify bioactive microbial metabolites from biocontrol agents to manage plant pathogens in critical crops. This study examined both volatile organic compounds (VOCs) and non-volatile compounds from Metarhizium carneum and Lecanicillium uredinophilum strains for their antimicrobial effects against various phytopathogens and analyzed their exo-metabolomes. M. carneum VOCs inhibited four bacterial and eight fungal species by up to 45.45%, while L. uredinophilum VOCs inhibited five bacterial and eight fungal species by up to 50.91%. Additionally, n-BuOH extracts from both biocontrol agents effectively targeted three fungi and five bacteria. The exo-metabolomes of M. carneum and L. uredinophilum included 125 and 102 spectrometric features, respectively, primarily consisting of polyketides, alkaloids, lipids, organic aromatic compounds, terpenoids, and peptides. Our findings revealed a correlation between the phylogenetic relationships of M. carneum strains, their bioactivity patterns against phytopathogens, and their metabolomic profiles. Notably, some compounds detected in both fungi previously demonstrated biological activity against plant pathogens, enhancing their biocontrol potential. This study not only evidences the antimicrobial properties of diffusible compounds from M. carneum and L. uredinophilum, but also documents the antimicrobial potential of their VOCs for the first time, supporting their use in sustainable agricultural practices, reducing reliance on chemical inputs.

Bioherbicide Potential of Eucalyptus saligna Leaf Litter Essential Oil.

We aimed to evaluate the bioherbicide potential of Eucalyptus saligna leaf litter essential oil, its fractions and major compounds. Six essential oil fractions were obtained by preparative thin-layer chromatography and analyzed by gas chromatography/mass spectrometry. Effects of the oil, its fractions and major compounds (1,8-cineole and/or α-pinene) diluted in aqueous solution were assessed on germination and seedling growth. Recipient species were Lactuca sativa (model), Amaranthus viridis (weed), Eragrostis plana (weed), and Paspalum notatum (forage). The essential oil was more phytotoxic on A. viridis and L. sativa, followed by E. plana, and caused no effects on P. notatum. Amaranthus viridis was inhibited by all treatments, mainly the essential oil, α-pinene and fraction 6, whereas E. plana was more affected by the oil fractions. Results revealed the species-specific phytotoxic effects of E. saligna essential oil, indicating its potential use for controlling A. viridis and E. plana. Phytotoxic effects of essential oils or their components should not be generalized, as effects may change according to recipient species.