Evaluation on composition, antioxidant and toxicity of Melaleuca cajuputi leaves

Chemical profiling and mechanistic insights into the antibacterial efficacy of Melaleuca cajuputi leaf extract

BACKGROUND

The emergence of antimicrobial resistance and the prevalence of bacterial infections have prompted the search for novel antimicrobials with diverse therapeutic potential from natural products. Thus, this study investigated the antibacterial efficacy of the leaf extracts of M. cajuputi. Additionally, the chemical composition and the mechanism of action of the most active extract (MAE) were evaluated.

METHODS

The antibacterial activity of leaf extracts of M. cajuputi was assessed using the broth microdilution assay. Scanning electron microscopy (SEM) was used to investigate the effects of MAE on the morphology of bacterial cells. Meanwhile, the chemical composition of the MAE was analyzed using Fourier transform infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS). AutoDock Vina was used for molecular docking analysis to unveil the interactions between the ligands and the active sites of the target bacterial proteins.

RESULTS

The crude extracts were obtained through cold maceration. The methanolic extract demonstrated the most significant antibacterial activity, with minimum inhibitory concentration (MIC) values spanning 0.25 mg/mL to 2 mg/mL. After 12 h of treatment with 1 × MIC of the methanolic extract, the bacteria showed discernible morphological alterations, including disrupted cell wall and membrane integrity. Thirty compounds were identified in the MAE and subsequently subjected to molecular docking studies against target bacterial proteins. Amongst the compounds, methylanthracene, cycloisolongifolene, diphenyl imidazole, benzil monohydrazone, and trimethoxybenzoic acid showed pronounced binding affinities towards Klebsiella pneumoniae membrane protein (PDB ID: 5O79), peptide binding protein (PDB ID: 7RJJ), Streptococcus agalactiae cell wall surface anchor (PDB ID: 2XTL), pilin (PDB ID: 3PHS), Staphylococcus aureus transglycosylase (PDB ID: 3VMQ), and penicillin-binding proteins (PDB ID: 3VSK). The binding energy scores for these interactions varied between - 6.0 kcal/mol and - 7.5 kcal/mol. Molecular dynamics simulations validated the stability of these interactions, reinforcing the in vitro findings of cell wall and membrane disruption​.

CONCLUSION

The findings of this study indicated that the methanolic extract of M. cajuputi leaves displayed potent antibacterial activity against Klebsiella pneumoniae, S. agalactiae, and S. aureus. The molecular docking analysis reveals significant binding interactions between the identified compounds and the target bacterial proteins, highlighting the potential of M. cajuputi as a novel source of anti-infectives targeting bacterial infections.

Exploring the Therapeutic Potential of Terpenoids for Depression and Anxiety

This review focus on the terpenoids as potential therapeutic agents for depression and anxiety disorders, which naturally found in a variety of plants and exhibit a wide range of biological activities. Among the terpenoids discussed in this review are α-pinene, β-caryophyllene, α-phellandrene, limonene, β-linalool, 1, 8-cineole, β-pinene, caryophyllene oxide, p-cymene, and eugenol. All of these compounds have been studied extensively regarding their pharmacological properties, such as neuroprotective effect, anti-inflammation, antibacterial, regulation of neurotransmitters and antioxidant effect. Preclinical evidence are reviewed to highlight their diverse mechanisms of action and therapeutic potential to support antidepressant and anxiolytic properties. Additionally, challenges and future directions are also discussed to emphasize therapeutic utility of terpenoids for mental health disorders. Overall, this review provides a promising role of terpenoids as novel therapeutic agents for depression and anxiety, with potential implications for the development of more effective and well-tolerated treatments in the field of psychopharmacology.

Histopathological Alterations in Gills, Liver and Kidney of African Catfish (Clarias gariepinus, Burchell 1822) Exposed to Melaleuca cajuputi Extract

This study evaluated the histopathological changes in the gill, liver and kidney of African catfish (Clarias gariepinus) intoxicated with a sub-lethal dose of Melaleuca cajuputi leaves extract (MCLE) for 96 h. The acute toxicity test has been determined previously with a value of 96-h LC50 = 127 mg/L, hence the selection of sub-lethal ranges from 60 mg/L to 160 mg/L of MCLE. Degenerative alterations were prominent in all tested organs, particularly after exposure to a high concentration of MCLE. Gill exhibited haemorrhage, epithelial lifting, lamellar disorganisation, and necrosis after exposure to a high MCLE concentration. Alterations in the liver include congestion, hydropic degeneration, and vacuolation, whereas lesions in the kidney were pyknosis, vacuolation, hydropic degeneration, and tubular necrosis. The obtained data showed that the organs experienced severe changes proportional to the increase in MCLE concentration. In addition, fish exposed to higher concentrations than the LC50 value experienced irreversible lesions. The present study suggests that the use of MCLE below the LC50 is recommended to avoid severe alterations to organs, particularly in African catfish. This study demonstrated that the use of MCLE above the LC50 promotes severe damage to the gills, liver and kidney of African catfish. However, further investigations are needed to define the causing-mechanisms underlying these effects.