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β-Carboline Alkaloids from Peganum harmala Inhibit Fusarium oxysporum from Codonopsis radix through Damaging the Cell
Zihao Zhu1,2, Shujuan Zhao1,2, Changhong Wang1,2
1The SATCM Key Laboratory for New Resources & Quality Evaluation of Chinese Medicine, Institute of Chinese Materia Medica, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, China.
Abstract:
Fusarium oxysporum is a widely distributed soil-borne pathogenic fungus that can cause medicinal herbs and crops to wither or die, resulting in great losses and threat to public health. Due to the emergence of drug-resistance and the decline of the efficacy of antifungal pesticides, there is an urgent need for safe, environmentally friendly, and effective fungicides to control this fungus. Plant-derived natural products are such potential pesticides. Extracts from seeds of Peganum harmala have shown antifungal effects on F. oxysporum but their antifungal mechanism is unclear. In vitro antifungal experiments showed that the total alkaloids extract and all five β-carboline alkaloids (βCs), harmine, harmaline, harmane, harmalol, and harmol, from P. harmala seeds inhibited the growth of F. oxysporum. Among these βCs, harmane had the best antifungal activity with IC50 of 0.050 mg/mL and MIC of 40 μg/mL. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results revealed that the mycelia and spores of F. oxysporum were morphologically deformed and the integrity of cell membranes was disrupted after exposure to harmane. In addition, fluorescence microscopy results suggested that harmane induced the accumulation of ROS and increased the cell death rate. Transcriptomic analysis showed that the most differentially expressed genes (DEGs) of F. oxysporum treated with harmane were enriched in catalytic activity, integral component of membrane, intrinsic component of membrane, and peroxisome, indicating that harmane inhibits F. oxysporum growth possibly through damaging cell membrane and ROS accumulation via regulating steroid biosynthesis and the peroxisome pathway. The findings provide useful insights into the molecular mechanisms of βCs of P. harmala seeds against F. oxysporum and a reference for understanding the application of βCs against F. oxysporum in medicinal herbs and crops.
Insights
Harmane, a natural compound from Peganum harmala seeds, effectively inhibits Fusarium oxysporum growth by damaging cell membranes and increasing reactive oxygen species (ROS). This offers a potential eco-friendly fungicide for crops and medicinal herbs.
Area of Science:
- Mycology
- Plant Biochemistry
- Molecular Biology
Background:
- Fusarium oxysporum causes significant crop and medicinal herb losses.
- Drug-resistant strains necessitate novel, eco-friendly antifungal agents.
- Plant-derived natural products offer potential as safe fungicides.
Purpose of the Study:
- To investigate the antifungal activity of Peganum harmala seed extracts against Fusarium oxysporum.
- To elucidate the molecular mechanisms underlying the antifungal action of β-carboline alkaloids (βCs).
- To identify the most potent βC for controlling F. oxysporum.
Main Methods:
- In vitro antifungal assays to determine growth inhibition.
- Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for morphological analysis.
- Fluorescence microscopy to assess reactive oxygen species (ROS) accumulation and cell death.
- Transcriptomic analysis to identify differentially expressed genes (DEGs).
Main Results:
- Peganum harmala seed extracts and five βCs inhibited F. oxysporum growth.
- Harmane exhibited the strongest antifungal activity (IC50 = 0.050 mg/mL, MIC = 40 μg/mL).
- Harmane induced cell membrane damage, ROS accumulation, and increased cell death.
- Transcriptomic analysis revealed DEGs related to steroid biosynthesis and peroxisome pathways.
Conclusions:
- Harmane is a potent antifungal agent against Fusarium oxysporum.
- Harmane's mechanism involves cell membrane disruption and ROS induction.
- These findings support the use of βCs from P. harmala as a basis for developing new fungicides.
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