Genetic Authentication of the Medicinal Plant Portulaca oleracea Using a Quick, Precise, and Sensitive Isothermal DNA Amplification Assay.

Portulaca oleracea (PO) is a commonly known medicinal crop that is an important ingredient for traditional Chinese medicine (TCM) due to its use as a vegetable in the diet. PO has been recorded to be frequently adulterated by other related species in the market of herbal plants, distorting the PO plant identity. Thus, identification of the botanical origin of PO is a crucial step before pharmaceutical or functional food application. In this research, a quick assay named "loop-mediated isothermal amplification (LAMP)" was built for the specific and sensitive authentication of PO DNA. On the basis of the divergences in the internal transcribed spacer 2 (ITS2) sequence between PO and its adulterant species, the LAMP primers were designed and verified their specificity, sensitivity, and application for the PO DNA authentication. The detection limit of the LAMP assay for PO DNA identification specifically was 100 fg under isothermal conditions at 63 °C for 30 min. In addition, different heat-processed PO samples can be applied for use in PO authentication in the LAMP assay. These samples of PO were more susceptible to the effect of steaming in authentication by PCR than boiling and drying treatment. Furthermore, commercial PO samples pursued from herbal markets were used to display their applicability of the developed LAMP analysis for PO postharvest authentication, and the investigation found that approximately 68.4% of PO specimens in the marketplace of herbal remedies were adulterated. In summary, the specific, sensitive, and rapid LAMP assay for PO authentication was first successfully developed herein, and its practical application for the inspection of adulteration in PO samples from the herbal market was shown. This LAMP assay created in this study will be useful to authenticate the botanical origin of PO and its commercial products.

Development of a specific and sensitive diagnostic PCR for rapid molecular authentication of the medicinal plant Portulaca oleracea.

Adulteration by Bacopa monnieri (BM) in Portulaca oleracea (PO) plants frequently occurs; it decreases the efficacy of traditional Chinese medicine (TCM) and leads to fraud in the herbal marketplace. In this study, a diagnostic PCR assay was established for the rapid authentication of PO and BM in the herbal market. The sequence divergences in internal transcribed spacer 2 (ITS2) between PO and its adulterant species were used to design diagnostic PCR primers. The specific designed primer sets were evaluated and show that the diagnostic PCR assay can be used to verify the authenticity of PO and BM. The detection limits of the primer set for PO and BM identification were 10 pg and 1 pg, respectively. The reactivity of diagnostic PCR was 0.1% PO genomic DNA and 0.01% BM genomic DNA in the test sample during DNA amplification. In addition, multiplex PCR (mPCR) for PO and BM identification was also established. The samples were more susceptible to the effect of steaming in authentication by singleplex PCR and mPCR than boiling and drying treatment. Furthermore, commercial samples from the market were used to demonstrate the applicability of the developed diagnostic PCR for PO authentication and diagnose BM adulteration, and the investigation found that approximately 72.2% (13/18) of PO plants in the herbal market were adulterated. In conclusion, the diagnostic PCR assay was successfully developed and its specificity, sensitivity and reactivity for PO and BM authentication were proven. These developed PCR-based molecular methods can be applied as an identification tool for PO authenticity and can be practically applied for inspection of BM adulteration in the herbal market in the future.