Antioxidant potential, total phenolic content and proposed structures of antioxidative chemical compounds from Curcuma longa leaves

Nowadays, the importance of natural sources in modern medicine cannot be underestimated as they exhibit remarkable antioxidant properties and total phenolic content (TPC). Therefore, the aim of this research is to investigate antioxidant potential through thin layer chromatographic (TLC) dot blot assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay of Curcuma longa leaves extracts, TPC using Folin-Ciocalteau method as well as proposed structures of antioxidative compounds through Gas Chromatography Mass Spectroscopy (GC-MS). The crude extracts of C. longa leaves were prepared by conducting consecutive maceration using organic solvent such as hexane, ethyl acetate and acetone. According to TLC dot blot assay, the acetone extract of C. longa scavenges the DPPH radical at the concentration of 0.024 mg/mL. The radical scavenging activity is in concentration dependent manner for all types of extracts. Acetone extract of C. longa shows the lowest concentration to scavenge 50% DPPH radical (IC50) at 460.40 ug/mL. Therefore, the polar extracts are known to be the most promising source of antioxidant agent compared to the less polar extract. The highest TPC value is calculated as 128.129 mg GAE/g sample. The antioxidative compounds are proposed as (Z)-9-methyl octadecenoate, Methyl hexadecanoate, 6,10,14-trimethyl-2-pentadecanone, Methyl octadecanoate, 4-pyridinol acetate, Octadecyl methacrylate and (E)-10-methyl octadecenoate. The results may be applicable to the medical and pharmaceutical industries as they provide basic scientific data for the development of new natural medicines from plant base.