Chlorogenic acid content, essential oil compositions, and in vitro antioxidant activities of Chromolaena odorata leaves.

Chromolaena odorata (L.) R. M. King and H. Rob. is a Thai medicinal plant used for the treatment of wounds, rashes, diabetes, and insect repellent. The leaves of C. odorata were collected from 10 different sources throughout Thailand. The chemical constituents of essential oils were hydro-distilled from the leaves and were analyzed by gas chromatography-mass spectrometry. Chlorogenic acid contents were determined by thin-layer chromatography (TLC) - densitometry with winCATS software and TLC image analysis with ImageJ software. The TLC plate was developed in the mobile phase that consisted of ethyl acetate:water:formic acid (17:3:2). Antioxidant activities were examined by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging and β-carotene bleaching assays. C. odorata essential oil has shown the major components of pregeijerene, dauca-5, 8-diene, (E)-caryophyllene, β-pinene, and α-pinene. The chlorogenic acid content of C. odorata leaves was determined by TLC-densitometry and TLC image analysis. Results have shown that TLC-densitometry and TLC image analysis method were not statistically significantly different. DPPH radical scavenging and β-carotene bleaching assays of ethanolic extract of C. odorata leaves showed its antioxidant potential.