Isolation, characterization, and immunological effects of alpha-galacto-oligosaccharides from a new source, the herb Lycopus lucidus Turcz.

This study was designed to isolate and characterize a mixture of alpha-galacto-oligosaccharides (GOS) from a new source, the roots of Lycopus lucidus Turcz. (RL), a traditional dietary treatment. In this study, the chemical components and immunological function of RL-GOS were investigated. HPLC analysis showed that the purified RL-GOS was a typical raffinose family oligosaccharide (RFO) with a high stachyose content of 51.8% (w/w), followed by 26.5% raffinose and 10.1% verbascose. Further functional evaluation showed that RL-GOS could elicit a significant increase (p < 0.05 vs control) in humoral immunity, as measured by plaque-forming cell (PFC) generation and serum hemolysin level in response to sheep red blood cells (SRBC) at all three tested doses of RL-GOS (0.75, 1.5, and 3.0 g/kg of BW) in mice. In addition, the cellular immune activity of RL-GOS was also demonstrated by enhancing in vivo delayed-type hypersensitivity (DTH) reaction to SRBC and spleenocyte proliferation response to concanavalin A (p < 0.05, compared with control group). Nevertheless, there were no significant differences in weight gain, lymphoid organ indices, and phagocytosis capacity following RL-GOS treatment. This study provides evidence for the discovery of a new GOS source (20% w/w GOS in fresh roots of L. lucidus Turcz.) and its potential application as an immune stimulant in functional foods.