Effect of ultra high pressure processing on immuno-modulatory activities of the fruits of Rubus coreanus Miquel

In this study, the most optimal extraction conditions as regards to the immuno-modulatory activity of Rubus coreanus were determined to be 500 MPa with water at 60 °C for 15 min (HPE15). The extraction yield under these conditions was estimated to be 17.3%, which was higher than the yield obtained from the conventional extraction process (13.9%) with water at 100 °C (NE100). For most cases, the extract obtained under a high pressure of 500 MPa for 15 min HPE15 contained higher concentrations of the three main phenolic compounds relative to the conventional extraction procedure; catechin — 5.48 mg/L vs. 3.11 mg/L, caffeic acid — 12.34 mg/L vs. 10.14 mg/L and ferulic acid — 6.94 mg/L vs. 2.59 mg/L. It was found that the high amounts of bioactive components in HPE15 had a stronger beneficial effect on the growth of human B cell (> 20%) and NK cell (> 15%). In addition, the secretion of cytokines, IL-6 (> 10%) and TNF-α (> 12%), and NO- (> 20%) production from macrophages treated with the HPE15 extract was also higher than when the cells were treated with NE100. Based on these combined findings, we concluded that the immuno-modulatory activities of the HPE15 could be enhanced by simultaneous responses of high concentrations of key active components and their synergistic effects. These results clearly proved that high pressure treatment over the appropriate extraction time could effectively destroy the cell membrane and allow the solvents to easily penetrate into the cytoplasm, which can result in the large release of immuno-modulatory active components with less heat damage.Industrial relevanceHigh pressure processing has been used for preservation purposes with no or minimal heat treatment where high temperature processing should be avoided. But, this process has not much studied yet on extracting useful compounds which are sensitive to heat from many food resources including medicinal plants even though this technology has many other advantages including a high yield and rapid extraction time within one hour without the need for thermal energy as well as with few impurities.Therefore, the results from this work about analyzing the ultra high pressure extraction process could definitely contribute to wide ranges of food industries for improving extraction yields correlated to their biological activities, which can expand this technology to process various natural resources having much nutritive and functional values as well as to overcome the mechanical limitations of manufacturing ultra high pressure extraction machines.

Research highlights
► Optimal extraction condition for enhancing immuno-modulatory activities was 500 MPa and 60 °C for 15 min.
► Under this condition, contents of catechin, caffeic acid and ferulic acid in the extracts were increased ca. two times.
► Immnue activities of the extract were enhanced due to both high amounts and synergistic effect of three flavonoids.
► Process time is most critical for improving immuno-modulatory activities under high pressure extraction condition