Gamma radiation is a physical process commonly used for the eradication of microorganisms distributed in food ingredients, medicinal plants and other bioresearches. The aim of this study was to investigate the effect of radiation dosage on the microbial load, chemical compounds and antioxidative characteristics of Polygoni Multiflori Radix (POMU). Ten commercial POMUs were purchased from different herbal markets and treated with 2 kGy, 4 kGy, 6 kGy, 8 kGy and 10 kGy gamma radiation doses to evaluate the microbial burdens of irradiated and unirradiated POMUs.
Our results confirmed that 2 kGy was sufficient for the inactivation of enterobacteria; at 4 kGy, mold and yeast counts were obviously reduced; and at 6 kGy, neither yeasts nor fungi were observed any longer.
The antioxidative effects and major antioxidant components of 0 kGy, 5 kGy, 10 kGy and 15 kGy irradiated POMU samples were also examined. Our results confirmed that 5 kGy irradiated POMU had both the highest antioxidative activity and lowest value in IC50 of DPPH radical-scavenging activity. The content of total phenols had no statistically significant changes. Therefore gamma irradiation at 8 kGy could be a potential method for decontaminate the microbial load of POMU to prolong shelf life and to improve hygienic quality.
Studies on Molecular Identification of Taraxacum formosanum and Distinguishing from Its Adulterants
Original identification of medicinal plants is important for quality control. In this study, the internal transcribed spacer 2 (ITS2) nuclear ribosomal DNA served as a DNA barcode and was amplified by allele-specific sequence-primed PCR; this approach was exploited to differentiate Taraxacum formosanum from five related adulterants. Using a set of designed PCR primers, a highly specific 250 bp PCR product of Taraxacum formosanum was successfully amplified by PCR. However, no product was amplified from any of the adulterants. This indicates that our allele specific primers have high specificity and can accurately discriminate Taraxacum formosanum from other 5 adulterant plants.
We also established a rapid, sensitive and specific loop-mediated isothermal amplification (LAMP) assay for authenticating Taraxacum formosanum. A set of four specific LAMP primers was designed ba sed on the nucleotide sequence of the internal transcribed spacer 2 (ITS2) nuclear ribosomal DNA (nrDNA) of TF. LAMP amplicons were successfully amplified and detected when genomic of TF was added in the LAMP reaction under isothermal condition (65℃) within 45 min. This specific LAMP primers have high specificity and can accurately discriminate Taraxacum formosanum from other adulterant plants; 1 pg of genomic DNA was determined to be the minimum concentration limit of the LAMP assay.
