This study proposes a simple methodology to construct the production curves of mycophenolic acid by Penicillium sp. (CASP5) and citrinin by Penicillium sp. (CATL1.1) in the crude extract, without any purification. The quantification of the compounds was done by 1H nuclear magnetic resonance (NMR) using the signal integration and an internal standard, N,N-dimethylformamide. Fungi were cultivated for a period of 20 days and quantification of the metabolites in the extracts was done starting from time zero, 2 days and after this period in an interval of 4 days. The maximum production of mycophenolic acid and citrinin was obtained at 12 and 8 days of fermentation, respectively. These results show that the 1H NMR technique was efficient to define the production curves of mycophenolic acid and citrinin directly in the crude extracts. In addition, the technique made it possible to evaluate the purity degree of the substances obtained in the extraction process. Furthermore, this is the first study that uses the 1H NMR technique to determine the production curves of secondary metabolites.