Study on the Dynamic Changes in Fungal Communities During the Storage of Polygalae Radix and the Antifungal Effects of Peppermint Essential Oil

Polygalae Radix, a traditional Chinese medicine for insomnia and memory disorders, is highly susceptible to fungal contamination and mycotoxin production (especially by <i>Aspergillus flavus</i>) during storage, compromising its safety and efficacy. Therefore, in this study, high-throughput sequencing was employed to evaluate the dynamic changes in fungal communities during the storage of Polygalae Radix and to analyze common mycotoxin-producing genera. Furthermore, the inhibitory effects of peppermint essential oil (PEO) on <i>A. flavus</i> were assessed through fumigation treatments, combined with colony counting and quantification of aflatoxins. Results showed the following: (1) Storage for 1-3 months significantly altered the fungal structure, promoting saprophytic and pathogenic fungi (e.g., <i>Wallemia</i>, <i>Paraphoma</i>, <i>Didymella</i>, <i>Cladosporium</i>…) and increasing the relative abundance of mycotoxin producers like <i>Penicillium</i>, <i>Aspergillus</i>, and <i>Fusarium</i> (notably, <i>Penicillium</i> increased from 0.28-2.33% to 5.39-80.43%). Additionally, <i>A. flavus</i>, capable of producing aflatoxins, was detected in samples stored for two months (RM2). (2) Antifungal tests demonstrated that PEO significantly inhibited the common fungi in Polygalae Radix. At 10 μL/g, it suppressed fungal growth and significantly reduced aflatoxin B₁ (AFB₁) and total aflatoxins (AFT, including AFB₁, AFB₂, AFG₁, and AFG₂) levels (<i>p</i> < 0.05). At 10 μL/g, AFB₁ and AFT were reduced to undetectable levels. PEO can serve as a green and effective protective strategy to inhibit <i>A. flavus</i> during the storage of Polygalae Radix and control aflatoxin contamination.