Monitoring Phenolic Compounds in Rice during the Growing Season in Relation to Fungal and Mycotoxin Contamination

Total phenolic content (TPC) and several phenolic acids present in rice grains were compared with fungal infection and mycotoxin presence throughout the growing season. Samples of 4 rice varieties were collected in 2018 and 2019 at 3 different plant phenological stages. Total fungal and main mycotoxigenic fungi incidence were checked and mycotoxin content was analysed. On the same samples, TPC and the concentration of 8 main phenolic acids (chlorogenic acid, caffeic acid, syringic acid, 4-hydroxybenzoic acid (4-HBA), p-coumaric acid, ferulic acid, protocatecuic acid and gallic acid) were measured. The results showed significant differences between years for both fungal incidence and mycotoxin presence. In 2018 there was a lower fungal presence (42%) than in 2019 (57%) while, regarding mycotoxins, sterigmatocystin (STC) was found in almost all the samples and at all growing stages while deoxynivalenol (DON) was found particularly during ripening. An interesting relationship was found between fungal incidence and TPC, and some phenolic acids seemed to be more involved than others in the plant defense system. Ferulic acid and protocatecuic acid showed a different trend during the growing season depending on fungal incidence and resulted to be positively correlated with p-coumaric acid and 4-HBA that seem involved in mycotoxin containment in field.