Antioxidant activity and cytotoxicity of Rang Chuet (Thunbergia laurifolia Lindl.) extracts

Thunbergia laurifolia Lindl. or Rang Chuet (RC) is widely described in Thai traditional medicine for protection against dietary and environmental toxicants with little substantiation. To better access the potential of RC as a medicinal plant, extracts were prepared by infusion with water, ethanol and acetone. Antioxidant activities and total phenolic content of RC extracts were evaluated using free radical scavenging, ferric reducing antioxidant power assay (FRAP) and the FolinCiocalteu method. It was found that water extraction of phenolic compounds was the most efficient ( 2433.9 mg GAE/100g) compared to ethanol and acetone extraction which had phenolic contents of 565 and 142.1mg GAE /100g, respectively. In addition, RC water extract possessed the highest antioxidant activities using free radical scavenging at the EC50 values of 0.13 mg GAE/mL, whereas ethanol and acetone extract showed EC50 at 0.26 and 0.61 mg GAE/mL respectively. Finally, the water extract also showed the highest total antioxidant activity using FRAP assay at 0.93 mmol/g followed by ethanol and acetone extracts (0.18 and 0.04 mmol/g). Extracts were subsequently investigated for their cytotoxicity. Cytotoxicity of RC crude extracts were investigated in L929, BHK(21)C13, HepG2 and Caco-2 cell lines. The toxicity was indicated at high concentrations over 100 μg/mL for all extracts, which would be the index for further recommended concentration use.