Optimization of Subcritical Water Extraction of Rosmarinic Acid from Perilla (Perilla frutescens L.) Seed Meal and Its Antioxidant Activity

Subcritical water extraction (SWE), a green and environmentally friendly extraction technology, was successfully used to extract rosmarinic acid from Perilla seed meal (PSM). Based on the results of single-factor experiments, three-factor and three-level of response surface methodology were used to optimize the extraction parameters of rosmarinic acid in PSM, including extraction temperature (140~180 ℃), extraction time (20~40 min) and solid-liquid ratio (1:30~1:50 g/mL). Meanwhile, the effects of SWE and several conventional extraction methods on the extraction yields of rosmarinic acid and their antioxidant activities (DPPH and ABTS free radical scavenging capacity) of PSM extracts were compared. The results showed that the optimized parameters were as follows: Extraction temperature 163 ℃, extraction time 30 min, and the ratio of solid to liquid 1:41 g/mL. Under these conditions, the extraction yield of rosmarinic acid was 4.91±0.16 mg/g dw, and the free radicals scavenging capacities of DPPH and ABTS were 10.62 and 13.46 mgV_C/g dw, respectively, which were significantly higher than those of several conventional extraction methods. In addition, scanning electron microscope (SEM) showed that the structure of the PSM residues became looser after SWE, which could benefit the extraction of rosmarinic acid.