In recent years, nutmeg (Myristica fragans Houtt.) has attracted considerable attention in the field of phytochemistry due to its diverse array of bioactive compounds. However, the potential application of nutmeg as a biorational for crop protection has been insufficiently explored. This study investigated the constituents of a nutmeg hydroethanolic extract via gas chromatography-mass spectrometry and vibrational spectroscopy. The research explored the extract’s activity against phytopathogenic fungi and oomycetes, elucidating its mechanism of action. The phytochemical profile revealed fatty acids (including tetradecanoic acid, 9-octadecenoic acid, n-hexadecanoic acid, dodecanoic acid, and octadecanoic acid), methoxyeugenol, and elemicin as the main constituents. Previously unreported phytochemicals included veratone, gelsevirine, and montanine. Significant radial growth inhibition of mycelia was observed against Botrytis cinerea, Colletotrichum acutatum, Diplodia corticola, Phytophthora cinnamomi, and especially against Fusarium culmorum. Mode of action investigation, involving Saccharomyces cerevisiae labeled positively with propidium iodide, and a mutant strain affected in ERG6, encoding sterol C-24 methyltransferase, suggested that the extract induces a necrotic type of death and targets ergosterol biosynthesis. The evidence presented underscores the potential of nutmeg as a source of new antimicrobial agents, showing particular promise against F. culmorum.

Curcuma longa, known for its anti-inflammatory, antioxidant, and antimicrobial properties, has been a staple in traditional medicine for centuries. In the pursuit of natural alternatives to synthetic preservatives, the extracts of C. longa have garnered attention for their efficacy in extending shelf life and preventing the spoilage of diverse agricultural products. This study aims to assess the antifungal and antioomycete activities and plant protection capabilities of a hydroethanolic C. longa extract as a natural product against crop pathogens. The phytochemical profile of the C. longa extract was elucidated through gas chromatography-mass spectrometry. The extract exhibited a richness in bisabolene sesquiterpenoids, notably (+)-β-turmerone, α-turmerone, (+)-(S)-ar-turmerone, and included minor phytoconstituents, such as α-atlantone, γ-curcumene, zingiberene, isoelemicin, and gibberellin A3. Radial growth inhibition assays demonstrated the C. longa extract’s effectiveness against various phytopathogenic fungi, including Botrytis cinerea, Colletotrichum acutatum, and Diplodia corticola, as well as the oomycetes Phytophthora cactorum and Phytophthora cinnamomi. In ex situ tests, the C. longa extract demonstrated remarkable protection capabilities for Malus domestica excised stems against P. cinnamomi-induced necrosis. Furthermore, the C. longa extract exhibited non-toxicity towards lettuce seed germination and did not impact early lettuce seedling growth, indicating its safety for crop protection. These findings contribute to expanding the potential applications of C. longa as an antimicrobial agent, particularly for safeguarding economically significant trees against the destructive oomycete P. cinnamomi.

Mushroom extracts have shown potential as a source of new antimicrobial agents. This study investigates the chemical profile of an aqueous ammonia extract obtained from the carpophores of Ganoderma lucidum, which grows on Quercus ilex trees, and explores its valorization as a biorational. The major chemical constituents of the extract, identified through gas chromatography–mass spectrometry, include acetamide, oleic acid, 1,2,3,4-butanetetrol, monomethyl azelate, undecane, and palmitic acid. The anti-oomycete and antifungal activity of G. lucidum extract was evaluated against Phytophthora cinnamomi, the primary threat to Quercus spp. in the dehesa biome, as well as three Botryosphaeriaceae fungi. In vitro tests revealed minimum inhibitory concentration (MIC) values of 187.5 μg·mL⁻¹ against P. cinnamomi and 187.5–1000 μg·mL⁻¹ against the fungi. Furthermore, conjugation of the G. lucidum extract with chitosan oligomers (COS) synergistically enhanced its antimicrobial activity, resulting in MIC values of 78.12 and 375–500 μg·mL⁻¹ against P. cinnamomi and the fungi, respectively. These MIC values are among the highest reported to date for natural products against these phytopathogens. Subsequent ex situ testing of the COS-G. lucidum conjugate complex on artificially inoculated Q. ilex excised stems resulted in high protection against P. cinnamomi at a dose of 782 µg·mL⁻¹. These findings support the potential utilization of this resource from the dehesa ecosystem to protect the holm oak, aligning with sustainable and circular economy approaches.