Characterization of the phytochemicals and antioxidant properties of extracts from Teaw ( Cratoxylum formosum Dyer)

Abstract

The leaves of the Thai vegetable, Teaw ( Cratoxylum formosum Dyer) were extracted with ethanol to provide an extract that had antioxidant properties. The composition of the extract was studied by high-performance liquid chromatography with a diode array detector, and by electrospray ionization mass spectrometry. The main antioxidant component (peak 1) was chlorogenic acid, which was present at 60% of the extract. Three minor components were present at 7%, 3% and 2%, and other components that were present at lower concentrations were also observed. Treatment of the Teaw extract with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH ) caused a similar reduction in peak area of 55.2–58.1% for chlorogenic acid and the three minor components, indicating that these components had common structural features. Component 2 was identified as dicaffeoylquinic acid, and compounds 3 and 4 were identified as ferulic acid derivatives. The radical-scavenging activity of the Teaw extract was compared with α-tocopherol, BHT and chlorogenic acid, using the DPPH and 2,2′-azinobis (3-ethylbenzothialozinesulfonic acid) radical cation (ABTS + ) assays. The Teaw extract scavenged both free radicals more strongly than did α-tocopherol and BHT, and the activity of the extract was consistent with the concentration of chlorogenic acid that was present, confirming that this component is a major contributor to the antioxidant activity. The acute toxicity of the Teaw leaf extract was investigated in mice, and it was found that the LD 50 of the extract was >32 g/kg. Consequently, this plant is a promising source of a natural food antioxidant.