Determination of caffeic acid content and antioxidant capacity of Thunbergia grandiflora and T. laurifolia leaves

Abstract

Introduction. Thunbergia grandiflora Roxb. a climbing shrub belonging to the Thunbergiaceae family, is very similar in appearance and habit to T. laurifolia or Rang Jued, a Thai traditional medicine which possess antioxidant activity. A few studies on phytochemical and antioxidant activity of T. grandiflora have been reported in this study, the ethanolic extracts of T. grandiflora and T. laurifolia leaves were subjected to investigate the quantity of caffeic acid as well as the free radical scavenging activity Methods, Plant materials were extracted with ethanol by reflux extraction method and filtered through filer paper Vacuum evaporation and lyophilization were used to obtain the dryness extracts. The extracts were determined for caffeic acid content using HPTLC method while evaluation of antioxidant activity of the extracts using DPPH assay. Results. The mobile phase of dichloromethane ethanol-formic acid 9:1:0/5 (ww provided a good resolution with an Ry value of 0:50 for caffeic acid at the wavelength of 254 nm. The Ry values and UV spectrum of caffeic acid from the sample extracts were Identical to those from the standard which indicated that both extracts contained caffeic acid. The caffeic acid content in T. grandiflora and T. laurifolia extracts were 3.2240 03 and 2 95+0.11 mg/g extract, respectively When the caffeic acid content in each fresh leaves was calculated, T. grandiflora leaves contained 20:54 mg caffeic acid per 100 g dry weight which was greater content than that of T. laurifolia leaves 70 mg caffeic acid per 100 g dry weight, In addition, the ethanolic extracts of T. grandiflora and T. laurifolia showed antioxidant activity with the IC50 values of 62:67 and 49:98 ug/ml, respectively Conclusion. T. grandiflora and T. laurifolia are climbing shrub with resemblance in appearance and habit. The flowers of these plants are similar but the leaves are different shape T. grandiflora leaves are cordate shaped with pubescent petioles while T. laurifolia leaves are ovate lanceolate shape. The results demonstrated that T. grandiflora leaves which consisted of caffeic acid and possessed antioxidant capacity can be used as a source of natural antioxidant However, further study on its safety should be evaluated.