Resveratrol-Schiff Base Hybrid Compounds with Selective Antibacterial Activity: Synthesis, Biological Activity, and Computational Study

Control of Bacterial Canker caused by Pseudomonas syringae pv. actinidiae (Psa) in kiwifruit plants by resinous exudates and extracts of Adesmia balsamica

BACKGROUND

Pseudomonas syringae pv. actinidiae (Psa) is the pathogen responsible for kiwifruit's bacterial canker, which produces significant economic losses. Effective treatments and measures to control this disease have not yet been found; it is currently controlled with many products containing heavy metals (especially copper) or antibiotics (especially streptomycin), which can cause serious phytotoxicity and antibacterial resistance problems. Therefore, it is essential to develop new strategies to control this disease by obtaining a product of natural origin of sustainable use, which is biodegradable and nontoxic to the environment, that could be used as biopesticide.

RESULTS

The ethyl acetate extract of Adesmia balsamica and the compound 2',4'-dihydroxychalcone (2,4-DHCH; 4) exhibited the same or similar antibacterial activity, respectively, as the positive control (commercial pesticide) at an effective concentration of 500 μg mL-1, on kiwifruit plants (Soreli variety) in vivo. Fluorescence microscopy revealed that one of the main modes-of-action by which it inhibits bacterial growth of Psa is by increasing membrane permeation, causing its disruption and intracellular alteration. Additionally, the application of the extract and 4 manages to control Psa bacterial canker disease by reducing gene expression related to the hrp W gene; Psa concentratiosn were specifically detected through real-time quantitative polymerase chain reaction (qPCR).

CONCLUSION

The ethyl acetate extract of A. balsamica effectively controls Psa in vitro and in vivo applied on kiwifruits plants, and therefore is a potential biopesticide for the control of bacterial canker in kiwifruit and potentially other crops. © 2025 Society of Chemical Industry.

Recent Advances in Resveratrol Derivatives: Structural Modifications and Biological Activities

Resveratrol, a naturally occurring phenolic stilbene molecule, has been intensively researched for its anti-inflammatory, anticancer, antioxidant, antibacterial, and neuroprotective properties. However, due to its limited absorption and probable hepatotoxicity, it is difficult to employ directly as a medication, limiting its therapeutic applicability. Over the last five years, numerous structural changes in resveratrol have been widely studied, resulting in considerable improvements in pharmacological activity and drug availability. This work reviews the biological activities and structure-activity relationships (SARs) of resveratrol derivatives, with the goal of providing useful insights for the discovery of new resveratrol derivatives.

Antibacterial and Antioxidant Activity of Synthetic Polyoxygenated Flavonoids

Flavonoids are an abundant class of naturally occurring compounds with broad biological activities, but their limited abundance in nature restricts their use in medicines and food additives. Here we present the synthesis and determination of the antibacterial and antioxidant activities of twenty-two structurally related flavonoids (five of which are new) by scientifically validated methods. Flavanones (FV1-FV11) had low inhibitory activity against the bacterial growth of MRSA 97-7. However, FV2 (C5,7,3',4' = OH) and FV6 (C5,7 = OH; C4' = SCH3) had excellent bacterial growth inhibitory activity against Gram-negative E. coli (MIC = 25 µg/mL for both), while Chloramphenicol (MIC = 25 µg/mL) and FV1 (C5,7,3' = OCH3; 4' = OH) showed inhibitory activity against Gram-positive L. monocytogenes (MIC = 25 µg/mL). From the flavone series (FO1-FO11), FO2 (C5,7,3',4' = OH), FO3 (C5,7,4' = OH; 3' = OCH3), and FO5 (C5,7,4' = OH) showed good inhibitory activity against Gram-positive MRSA 97-7 (MIC = 50, 12, and 50 µg/mL, respectively), with FO3 being more active than the positive control Vancomycin (MIC = 25 µg/mL). FO10 (C5,7= OH; 4' = OCH3) showed high inhibitory activity against E. coli and L. monocytogenes (MIC = 25 and 15 µg/mL, respectively). These data add significantly to our knowledge of the structural requirements to combat these human pathogens. The positions and number of hydroxyl groups were key to the antibacterial and antioxidant activities.

Anti-listerial peptides from a marine Bacillus velezensis FTL7: production optimization, characterizations and molecular docking studies

Antimicrobial peptides (AMPs) with potent anti-listerial activity were characterized from a novel marine Bacillus velezensis FTL7. A Box-Behnken statistical experimental design was used to study the combined impact of culture conditions on the production of AMPs by B. velezensis FTL7. The conditions optimized by statistical experimental design were 34.5 °C incubation temperature, 23 h incubation time, and 7.6 initial pH of the medium. AMP purification was performed by ammonium sulphate fractionation and butanol extraction followed by reversed-phase C18 solid-phase extraction. Tricine-SDS-PAGE analysis revealed a peptide with a molecular mass of ~ 6.5 kDa in an active AMPs fraction, whereas the mass spectrometry (MS) analysis showed the presence of AMPs in the mass range of 1-1.6 kDa, along with a 6.5 kDa peptide. Both MS and MS/MS analysis confirmed the AMPs as lipopeptides including surfactin, fengycins and iturin A and a circular bacteriocin amylocyclicin. The minimum inhibitory concentration of these AMPs against L. monocytogenes Scott A was 2.5 µg/mL. Further, the in-silico docking studies showed that the AMPs from B. velezensis FTL7 have high binding energy and stable binding patterns towards L. monocytogenes target proteins. Thus, this new combination of AMPs can serve as an effective food bio-preservative.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03944-5.