A Promising Source of Natural Fungicides and Herbicides

Authors: Tamang, Prabin; Bajsa Hirschel, Joanna; Pan, Zhiqiang; Barickman, Thomas; Kim, Seong Jong; ZHELJAZKOV, VALTCHO - Washington State University; PAUDEL, PRADEEP - University Of Mississippi; Cantrell, Charles

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2025
Publication Date: 6/1/2025
Citation: Tamang, P., Bajsa Hirschel, J.N., Pan, Z., Barickman, T.C., Kim, S., Zheljazkov, V.D., Paudel, P., Cantrell, C.L. 2025. A Promising Source of Natural Fungicides and Herbicides. Journal of Agricultural and Food Chemistry. https://doi.org/10.1021/acs.jafc.5c03113.
DOI: https://doi.org/10.1021/acs.jafc.5c03113

Interpretive Summary: Pogostemon cablin Benth., commonly known as patchouli, is a fragrant herb that has been known for its medicinal use for centuries. It’s essential oil (EO), an already FDA-approved ingredient, is widely utilized in perfumery and traditional medicine to treat colds, fever, headaches, and nausea. In our study, patchouli EO exhibited antifungal activity against crop fungal pathogens. Therefore, we further explored its composition and identified two key compounds: patchouli alcohol (patchoulol) and pogostone. We examined the antifungal and phytotoxicity properties of both compounds. Although both compounds displayed antifungal activity, pogostone demonstrated stronger efficacy against several fungal pathogens that threaten small fruit crops compared to patchoulol. Interestingly, pogostone also exhibited potent herbicidal activity against palmer amaranth (Amaranthus palmeri), showing effectiveness comparable to the common weed killer glyphosate. This discovery suggested that pogostone could serve as a natural, dual-purpose solution in agriculture helping to combat both fungal diseases and weeds. This finding could be significant for agriculture, potentially offering a more natural and eco-friendlier crop-protection strategy.

Technical Abstract: Pogostemon cablin, commonly known as patchouli, belongs to the Lamiaceae family and is a fragrant herb that has been used for various therapeutic applications since ancient times. In-house antifungal screening programs identified P. cablin essential oil (EO) as a potent fungicide against the small fruit fungal pathogen Colletotrichum fragariae leading us to perform a bioassay-directed fractionation to determine the bioactive constituent(s) responsible for the activity. This process identified patchoulol and pogostone as the antifungal constituents responsible for the activity of the EO. Dose-response evaluation indicated pogostone was a more active compound, with IC50 values of 8.5±0.5, 2.34±0.13, 7.74±0.23, and 6.34±0.85 µg/mL against C. fragariae, C. gloeosporioides, C. acutatum, and B. cinerea, respectively at 48 h. Pogostone was also evaluated for its phytotoxicity due to its perceived structural similarities to '-triketone herbicides, which are known to inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD). Against Lemna paucicostata, pogostone exhibited an IC50 of 0.9±0.1 mM comparable to the commercially available herbicide atrazine with an IC50 of 1.1±0.23 mM, prompting further phytotoxicity determinations. Pogostone (1%) was evaluated for post-emergence activity against palmer amaranth (Amaranthus palmeri), showing significantly greater activity than solvent control and no significant difference compared to glyphosate (2%). Photosynthetic efficiency evaluations of pogostone against Arabidopsis thaliana suggest that photosystem II may not be the primary target of pogostone. Molecular modeling evaluations against plant HPPD suggest that pogostone may exert its phytotoxic effects through a different mechanism of action. These findings suggested the potential of pogostone as a single tool with both antifungal and herbicidal properties.