An investigation of fungal contamination on the surface of medicinal herbs in China

Background: The dried parts of medicinal herbs are susceptible to the infection of fungi during pre- or post-harvest procedure. This study aimed to investigate the presence of fungi and their metabolites mycotoxins on the surface of medicinal herbs collected from China. Methods: Forty-five retail samples of 15 different medicinal herbs were collected from 3 different regions in China. Then the potential fungi were immediately washed off from the surface of each sample with 0.1% Tween-20 followed by incubation of the rinse on petri-dish with potato dextrose agar containing chloramphenicol at 28 degrees C. The obtained fungi were isolated as single colonies and then characterized by morphology and molecular identification using internal transcribed spacer (ITS) sequencing with extracted DNA. Meanwhile, the mycotoxin-producing potential of the isolates was studied by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results: A total of 126 fungi were identified from the surface of samples by morphology and ITS sequencing, with Aspergillus and Penicillium genera as the predominant contaminants. The mycotoxin-producing potential analysis showed that 6 of 8 A. versicolor isolates could produce sterigmatocystin. All 3 A. aculeatus isolates produced ochratoxin A, but only 1 of 3 A. flavus strains produced aflatoxins B-1 and B-2 without G(1) and G(2). Although the sample contamination ratios were high (>= 95.6%), there was no significant difference (chi(2) = 1.05, P = 1.0) among the samples from 3 regions, which demonstrates the prevalent fungal contamination in the herbal medicines. Conclusion: The prevalent contamination phenomenon of fungi and high potential risk of sterigmatocystin and ochratoxin A were observed in 45 medicinal herbs collected from China.