Aflatoxin B1-producing aspergillus in sun-dried medicinal plant materials

Fifty sun-dried medicinal plants were obtained from traditional drug stores in Songkhla Province, Thailand, and examined for Aspergillus and aflatoxin B sub(1). 288 isolates of Aspergillus were obtained by standard blotter plate and 25 species were identified. The most common species were A. niger with 99 isolates, A. flavus 84 isolates, A. terreus 33 isolates, A. oryzae 25 isolates, A. nidulans (Emericella nidulans) 10 isolates, A. fumigatus 9 isolates and A. chevalieri (Eurotium chevalieri) 8 isolates. The other species [A. alliaceus, A. auricomus, A. carbonarius, A. carneus, A. clavatus, A. fischeri (Sartorya fumigata), A. janus, A. melleus, A. ochraceus, A. phoencis, A. sparsus, A. terricola, A. thomii, A. versicolor, A. wentii and Aspergillus sp.1-3] each had 1-2 isolates. Of the 50 different plants examined, 9 had no trace of Aspergillus, namely Cinnamomum zeylanicum, Illicium verum, Andrographis paniculata, Carthamus tinctorius, Eugenia caryophyllus, Elettaria cardamomum, Coriandrum sativum, Curcuma longa and Cassia garrettiana. The highest number of species (9) of Aspergillus was found on Rauvolfia serpentina. The ability of Aspergillus to form aflatoxin was determined in coconut milk agar by observing the intensity of blue fluorescence in agar surrounding the colonies under ultraviolet light and the yellow pigment under the colonies. The results showed that production of aflatoxin was limited to the one species, A. flavus, from which 84 isolates produced aflatoxin in 57 isolates (67.8 percent). Aflatoxin B sub(1) production was confirmed by culturing fluorescencing isolates of A. flavus in coconut milk broth and detecting by ELISA technique. Aflatoxin B sub(1) showed increasing production after 2 days, stabilizing at 3-4 days, and then decreasing after 5-6 days. Aflatoxin B sub(1) could not be detected from non-fluorescencing isolates. The morphological characteristics of the aflatoxin B sub(1)-producing and non-producing strains of A. flavus were similar under light microscope and scanning electron microscope. Using the ELISA technique, all medicinal plants sampled showed aflatoxin B sub(1), with the highest contamination being found in Cassia garrettiana at 1,101.8 ppb, Caesalpinia sappan 655.9 ppb, Cassia siamea 583.0 ppb and Smilax ferox 572.5 ppb. Only 16 kinds of medicinal plant had levels of aflatoxin B sub(1) lower than WHO guidelines (20 ppb) specifically Smilax japonica, Derris scandens, Myristica fragrans, Piper spp., Curcuma zedoaria, Zingiber purpureum, Piper retrofractum, Elettaria cardamomum, Curcuma longa, Imperata cylindrica, Rhinacanthus nasutus, Kaempferia pulchra, Foeniculum vulgare, Diospros decandra, Bosenbergia pandurata and Alyxia reinwardtii.