Antifungal and Zearalenone Inhibitory Activity of Ocimum sanctum L. Essential Oil on Fusarium graminearum Determined by UHPLC and RT-qPCR

Fusarium graminearum has been given special attention in the context of agricultural commodities due to its ability to grow in diverse climatic conditions, and to produce different mycotoxins including zearalenone (ZEA) and type-B trichothecenes, which cause ill health effects on humans, animals and plants. The application of synthetic antifungal agents for the control of F. graminearum result in negative health impacts in livestock and humans and the upsurge of resistant organisms as well. Therefore, there is a need to propose proper food grain management practices, including the application of herbal antifungal and mycotoxin controlling agents, to reduce the growth of toxigenic F. graminearum as well as the production of ZEA in agricultural commodities. Ocimum sanctum also known as Holy Basil or Tulsi is widely used as a medicinal plant in Ayurveda. The current protocol demonstrates to quantify the antifungal activity of O. sanctum L. essential oil (OSEO) as reflected by the decreased F. graminearum growth and ZEA production. Antifungal activities of OSEO are carried out by micro well dilution method and further validated quantitatively by scanning electron microscopic methods. Effects of OSEO on ZEA production is analysed by Quantitative reverse transcription PCR (RT-qPCR) and Ultra high performance liquid chromatography (UHPLC) methods from a broth culture of F. graminearum. Anti-mycotoxic efficacy of OSEO is assessed directly on F. graminearum inoculated maize grains. The protocol efficiently assessed the activity of OSEO as an herbal antagonistic agent against fungal infestation and ZEA production by F. graminearum. The protocol can be used to test a wide variety of herbal compounds for antifungal activity against F. graminearum or with modifications on other mycotoxigenic fungi, an important intervention in food safety and processing industries where the fungal infestation is a major concern.