Drug-resistant bacteria constitute a big barrier against current pharmacotherapy. Efforts are urgent to discover antibacterial drugs with novel chemical and biological features. Our work aimed at the synthesis, evaluation of antibacterial effects, and toxicity of licochalcone C (LCC), a naturally occurring chalcone. The synthetic route included six steps, affording a 10% overall yield. LCC showed effects against Gram-positive bacteria (MIC = 6.2–50.0 µg/mL), Mycobacterium species (MIC = 36.2–125 µg/mL), and Helicobacter pylori (MIC = 25 µg/mL). LCC inhibited the biofilm formation of MSSA and MRSA, demonstrating MBIC₅₀ values of 6.25 μg/mL for both strains. The investigations by fluorescence microscopy, using PI and SYTO9 as fluorophores, indicated that LCC was able to disrupt the S. aureus membrane, similarly to nisin. Systemic toxicity assays using Galleria mellonella larvae showed that LCC was not lethal at 100 µg/mL after 80 h treatment. These data suggest new uses for LCC as a compound with potential applications in antibacterial drug discovery and medical device coating.

Even though Brazil has a large biodiversity of medicinal plants, many of them have not had their chemical and biological potential acknowledged. Several medicinal plants are rich in secondary metabolites with broad antibacterial activity, a relevant fact since many pathogenic bacteria are resistant to conventional antibiotics. Psidium myrtoides, a species of plant in the Myrtaceae family that is known for its sweet purple fruit, should be highlighted in this field. It is a medicinal plant with strong antibacterial, antifungal, anti-inflammatory, antioxidant, antitumoral, and herbicidal potential. This study aimed at investigating, for the first time, the antibacterial activity of hexane extracts from P. myrtoides dry leaves – which were collected in both dry and rainy seasons – and the dry pericarp of unripe fruit. Their antibacterial activity was evaluated in vitro by the broth microdilution method on 96-well plates, and their Minimum Inhibitory Concentration (MIC) values were expressed as µg/mL. The following bacteria were assayed: Streptococcus mutans, S. sobrinus, S. mitis, S. salivarius, S. sanguinis, Enterococcus faecalis, Lactobacillus casei, Xanthomonas citri (resistant, tolerant, and sensitive to copper), Mycobacterium tuberculosis, M. avium, and M. kansasii. The resulting MIC values of all extracts under study were promising since they ranged from 31.25 to 500 µg/mL. This study revealed the in vitro potential of P. myrtoides against different bacterial strains and reinforced the need for further phytochemical investigations that aim at isolating its bioactive chemical constituents.

Although Aspidosperma subincanum Mart. is traditionally used for metabolic and digestive disorders, its volatile nonpolar fraction remains unexplored. This study investigated n-hexane extracts from leaves (HE-GL) and stem bark (HE-GS), targeting antibacterial and enzyme-inhibitory activities based on ethnopharmacological use. GC-MS analysis revealed β-caryophyllene and aromadendrene as major constituents. HE-GL showed strong activity against Xanthomonas citri (MIC/MBC = 50 µg/mL), while HE-GS showed moderate effects (200 µg/mL). Both extracts exhibited acetylcholinesterase inhibition (IC₅₀ ≈ 80 µg/mL) and weak α-amylase and elastase inhibition (IC₅₀ ≥ 500 µg/mL). Cytotoxicity assays in human tumour (HeLa, MCF-7, U-251MG) and non-tumour (GM07492A) cell lines showed no effects up to 250 µg/mL. Molecular docking supported interactions with acetylcholinesterase and bacterial targets. These findings highlight the antibacterial and cholinesterase-modulating potential of A. subincanum volatiles.

Chemical compositions of essential oils (EOs) from Pelargonium graveolens (EO-PG), Lavandula angustifolia (EO-LA) and Cananga odorata (EO-CO) flowers were determined by GC-MS and GC-FID. Antibacterial activities were determined by the microdilution broth method in 96-well culture plates and MIC and MBC values were expressed as mg/mL. EOs were assayed individually and showed to be active against Xanthomonas citri, X. euvesicatoria, X. vasicola, X. campestris, Pseudomonas fluorescens, Xylella fastidiosa, Burkholderia cepacia, Pantoea ananatis, Pectobacterium carotovorum and Ralstonia solanacearum at concentrations between 0.31 and 10 mg/mL. Blend 2 (EO-PG: EO-LA: EO-CO 3:1:1), out of the three blends prepared by this study, was the most promising one since it exhibited the lowest values of MIC and MBC, i.e., between 0.31 and 1 mg/mL. In short, this study showed, for the first time, that EOs and their blends may be promising tools in agricultural defense to prevent severe bacterial diseases in plants.