Exposure assessment of lovastatin in Pu-erh tea

Abstract

This paper reports the results of an extensive survey on the levels of lovastatin in Pu-erh tea samples. The microbial source of lovastatin was assessed by testing the ability of fungi with higher isolation frequency in the Pu-erh tea samples to produce lovastatin on Czapek yeast extract agar (CYA). Lovastatin was not detected in any of the raw Pu-erh tea samples without storage but was found in almost all the ripe Pu-erh tea samples, with lovastatin contents ranging from 20.61 ng/gdw to 226.38 ng/gdw. After five years' storage, the lovastatin levels increased obviously in ripe Pu-erh tea samples and 55% of raw Pu-erh tea samples from 2007 were found to contain lovastatin with concentrations ranging between 28.41 ng/gdw and 228.61 ng/gdw. With increasing storage time, lovastatin concentration in ripe Pu-erh tea, and the occurrence and concentration of lovastatin for raw Pu-erh tea increased significantly. Three genera of fungi: Aspergillus, Penicillium and Trichoderma were often isolated from Pu-erh tea samples. A total of 40 strains from 3 fungal genera were selected to test their ability to produce lovastatin. Only 6 strains, Aspergillus tubingensis, Aspergillus wentii, Aspergillus fumigatus, Penicillium chrysogenum, Trichoderma asperellum and Trichoderma citrinoviride, were able to produce lovastatin reaching concentrations of 9.59 ± 0.42 ng/g CYA, 2.33 ± 0.21 ng/g CYA, 2.77 ± 0.13 ng/g CYA, 3.36 ± 0.69 ng/g CYA, 4.8 ± 0.17 ng/g CYA, and 1.47 ± 0.36 ng/g CYA respectively in Czapek yeast extract agar.