Extraction of brown pigment from Rosa laevigata and its antioxidant activities

Rosa laevigata Michx. (Rosaceae), widespread in China, contains many valuable nutrients and has long been used as food and medicine in Chinese folklore. Nowadays, due to its favorable property of coloring, the brown pigment of R. laevigata has an attractive potential as an available additive in food.

The aims of this study were to optimize the extraction process of brown pigment from R. laevigata and investigate its antioxidant activities on the basis of its abilities to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical and superoxide radical.

Extraction conditions of brown pigment from R. laevigata were investigated through an orthogonal design of L₉(3)⁴ assay. Ethanol concentration, extraction temperature, time, and ratio of material to solvent were the main factors affecting the extraction rate. Subsequently, the antioxidant activity of brown pigment was assessed using DPPH method, while hydroxyl radicals and superoxide free radicals were respectively determined by the Fenton-RhB (Rhodamine B) system and using the pyrogallol-luminol system.

The optimum extraction conditions were determined: temperature 70°C, ethanol concentration was 60%, extraction time 2 h and ratio of material to solvent was 1:6. Brown pigment showed a good radical scavenging activity, and exhibited a concentration-dependent inhibition of hydroxyl radical and superoxide free radical at low concentrations. When the concentration of brown pigment was 1 mg/mL, the scavenging percentage of hydroxyl radical reached 67.33%.

The brown pigment of R. laevigata could potentially be used as a promising natural antioxidant in the food and pharmaceutical industries.