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Research articles

ScienceAsia 39 (2013): 124-133 |doi: 10.2306/scienceasia1513-1874.2013.39.124

Authentication of the Thai medicinal plants sharing the same common name `Rang Chuet': Thunbergia laurifolia, Crotalaria spectabilis, and Curcuma aff. amada by combined techniques of TLC, PCR-RFLP fingerprints, and antioxidant activities

Pipob Suwanchaikasem, Thatree Phadungcharoen, Suchada Sukrong*

ABSTRACT:     The herbal drug known as `Rang Chuet' has been widely used in traditional Thai medicine for the treatment of poisoning. However, at least three medicinal plants, Thunbergia laurifolia, Crotalaria spectabilis, and Curcuma aff. amada, share this name. Because of the similarity in nomenclature, the commercial products are considered authentic and have been effectively used as herbal drugs. Therefore, the aims of this study were to compare the biological activities of these plants with antioxidant assays and to establish a reliable method to identify the original plant species. T. laurifolia exhibited the highest free-radical-scavenging and ferric-reducing properties of the three aqueous extracts. Crotalaria spectabilis exhibited the highest antioxidant activity when ethanolic extracts were investigated. The total phenolic content was associated with the antioxidant capacities of the extracts. Thin-layer chromatography (TLC) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods were used to differentiate the three species. In the TLC analysis, characteristics of flavonoids in the ethanolic extracts and of phenolic compounds in the aqueous extracts were observed for T. laurifolia and Crotalaria spectabilis but not for Curcuma aff. amada. Variable sites in the matK genes of the three species were identified and can be recognized by the restriction enzymes DdeI and HaeIII. In summary, the TLC and PCR-RFLP fingerprints established in this study can be used to discriminate between T. laurifolia, Crotalaria spectabilis, and Curcuma aff. amada. As `Rang Chuet' samples from different plant origins differ in their antioxidant potency, the substitution of these medicinal plants should be recognized.

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Department of Pharmacognosy and Pharmaceutical Botany, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Bangkok 10330 Thailand

* Corresponding author, E-mail: suchada.su@chula.ac.th

Received 23 Jul 2012, Accepted 27 Feb 2013