Identification of volatile oil and optimization of the extraction process for polysaccharides of Oenothera rosea L'Hér. ex Aiton using response surface methodology.

Oenothera rosea L'Hér. ex Aiton has demonstrated certain medicinal and animal feed applications, while further investigation into its active ingredients remains urgently needed. Thus, this study was designed to extract volatile oil using steam distillation, followed by component identification via GC-MS. Additionally, response surface methodology was employed to optimise the extraction process of crude polysaccharides from Oenothera rosea L'Hér. ex Aiton. The optimal conditions were determined as follows: ultrasonic time of 57 min, sample-solvent ratio of 24 (mL/g), extraction time of 62 min, and extraction temperature of 63 °C, achieving a maximum crude polysaccharides content of 6.54%. Moreover, antioxidant activities of the obtained volatile oil and crude polysaccharides were explored. The IC50 values of the volatile oil and crude polysaccharides were 6.26 mg/mL and 0.43 mg/mL for DPPH radical scavenging, and 4.47 mg/mL and 0.78 mg/mL for ABTS radical, respectively. These findings provide a preliminary theoretical foundation for future research.