Total phenolic content and antioxidant activity of Ulam raja (Cosmos caudatus) and quantification of its selected marker compounds: Effect of extraction

Abstract

The effect of heating time (30, 45, and 60 min) and temperature (45, 65, and 85°C) on the extraction yield (total soluble solids) of Ulam raja (Cosmos caudatus) was studied using face-centered composite design-response surface methodology. Total phenolic content and antioxidant activity (TEACDPPH) of samples obtained by aqueous extraction under different temperature and time were determined using Folin–Ciocalteau and 2,2-diphenyl-1-picrylhydrazyl scavenging activity assays, respectively. The yield, total phenolic content, and TEACDPPH of Ulam raja extracts ranged as 3.0–4.2 °Brix, 36.09–37.76 mg gallic acid equivalent/g, and 121.17–146.84 µmol Trolox equivalent/g of plant material on dry basis, respectively. Yield and TEACDPPH of samples were significantly influenced (p < 0.05) by the extraction conditions. Meanwhile, no significant effect (p > 0.05) on total phenolic content was observed. Extraction of Ulam raja at 85°C for 30 min resulted in higher yield and TEACDPPH of the extract. The chromatographic and spectral data confirmed the presence of several flavonoids in the lyophilized Ulam raja extract, i.e., quercitrin, catechin, and rutin, and their quantities were also reported as 36.9, 25.0, and 8.2 mg/g of Ulam raja extract, respectively.