Standardization of leaf and stem of Thunbergia Laurifolia and quantitative analysis of rosmarinic acid in selected Thai medicinal plants

Abstract

Rang-Jued or Thunbergia laurifolia Lindl. is a species in family Thunbergiaceae. In Thailand, leaf and stem of T. laurifolia are used to treat fever, inflammation, as well as antidotes. Perilla frutescens (L.) Britton or Nga-Kee-Mon belongs to Labiatae family. The leaf of P. frutescens is used to treat allergy, fever and inflammation. Rosmarinic acid is the active compound in both plants which was used as a standard marker in this study. Quantification of rosmarinic acid in the three samples using TLC-densitometry and TLC-image analysis were not statistically significantly different (P > 0.05). The pharmacognostic specification of T. laurifolia leaf and stem including macroscopic evaluation, microscopic evaluation, physico-chemical parameters and chemical fingerprints were established in order to provide the quality control for medicinal plant as per World Health Organization recommended. In vitro biological activities indicated that the ethanolic extracts of T. laurifolia leaf and stem as well as rosmarinic acid had antioxidant and anti-diabetic potentials. Furthermore, both T. laurifolia ethanolic extracts and rosmarinic acid showed non-toxicity to cancer and normal cell lines according to standard criteria. However, the comet assay showed that the three test samples exhibited DNA damage in human lymphocytes which were proportional to the concentration.