Extraction process optimization and activity assays of antioxidative substances from Rheum officinale

In the present work, we optimized the ultrasound-assisted extraction condition of antioxidative substances from Rheum officinaleby orthogonal experiment followed by response surface methodology. The obtained ethanol extract of R. officinale(EER) was further investigated with its antioxidant activity, the effect on extending the longevity of Drosophila melanogasterand antibacterial activity against Propionibacterium acnes.The results showed that the EER extracted under the condition of solid–liquid ratio of 1:43, ultrasonic extraction time of 8 min and ethanol concentration of 50% got the highest radical scavenging (92.95 ± 1.82%), whose antioxidant activity was close to ascorbic acid and butylated hydroxytoluene. In Longevity assay, male flies were fed extract with a range from 50 to 200 mg/L and the result showed a good work on extending the lifespan of fruit flies. In antibacterial assays, the EER exhibited a moderate antibacterial ability. Moreover, it is found that Rhein could be the main constituent against Propionibacterium acnes. Therefore, R. officinalecould be developed continuously for application in medical, cosmetic and anti-aging field, due to its potential antioxidant, anti-P. acnesand anti-aging activities.