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 Aspergillus flavus) 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 A. flavus 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., Wallemia, Paraphoma, Didymella, Cladosporium…) and increasing the relative abundance of mycotoxin producers like Penicillium, Aspergillus, and Fusarium (notably, Penicillium increased from 0.28–2.33% to 5.39–80.43%). Additionally, A. flavus, 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 (p < 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 A. flavus during the storage of Polygalae Radix and control aflatoxin contamination.