Separation and quantification of mycotoxins in floral tissue of hemp (Cannabis sativa) infected with Fusarium graminearum

Background

The fungal pathogen Fusarium graminearum produces mycotoxins when it infects grains. This pathogen also infects hemp (Cannabis sativa L. containing less than 0.3% tetrahydrocannabinol or THC). The presence of trichothecene mycotoxins like deoxynivalenol (DON) has not been reported in floral tissue of hemp infected with F. graminearum. The object of this study was to develop a method to extract three trichothecene mycotoxins—DON, 3-acetyldeoxynivalenol (3-ADON), and 15-acetyldeoxynivalenol (15-ADON)—from hemp floral tissue, and to quantify the mycotoxins by high-performance liquid chromatography (HPLC) with ultraviolet detection.

Results

Standards of nivalenol (NIV), DON-3-glucoside (D3G), DON, 3-ADON, and 15-ADON were separated from each other and from standards of several cannabinoids. Standard curves were linear (R-squared values >0.99). Recoveries from hemp spiked with 36 μg/g mycotoxins were 86%–90% for DON, 75%–77% for 15-ADON, and 86%–101% for 3-ADON. In extracts of hemp inflorescences infected with different strains of F. graminearum (15-ADON chemotypes), DON was detected in one sample. Other samples contained 15-ADON but no detectable DON, or neither mycotoxin in detectable amounts.

Conclusion

Mycotoxins were separated from cannabinoids. DON was also separated from matrix components, and 15-ADON and 3-ADON were partially separated from matrix components. The presence of DON in hemp may depend on fungal strain or stage of disease development, as well as the sensitivity of the method. The current method could quantify DON and 15-ADON at about 3 μg/g in hemp floral tissue, and 3-ADON at about 6 μg/g.