The physicochemical properties and immunomodulatory activities of gardenia yellow pigment from gardenia fruit

Gardenia yellow pigment (GYP) was isolated from Gardenia jasminoides fruit. GYP possess various beneficial biological activities, but its immunomodulatory activity remains incompletely known. In present study, we evaluated the stability of GYP at different temperature, light, pH, and metal ions firstly. The antioxidant capacity of GYP was then evaluated by 1, 1-Diphenyl-2-picrylhydrazyl radical (DPPH), 2, 2 '-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), Ferric ion reducing antioxidant power (FRAP), and Hydroxyl radicals. Finally, the immunomodulatory activities and underlying mechanism of GYP were determined using RAW264.7 cells. The results indicated that the stability of GYP was greatly affected by higher temperature (60-100 celcius), ultraviolet radiation, acid, alkali, and Fe3+. Furthermore, GYP exhibited strong antioxidant activity, and the IC50 values of DPPH, ABTS, and Hydroxyl radicals were 0.44, 0.07, and 0.09 mg/mL, respectively. Meanwhile, FRAP value was 1.65 +/- 0.04 mM FeSO4 at the GYP concentration of 0.11 mg/mL. The cell experiment exhibited that GYP significantly enhanced the proliferation and phagocytosis of macrophages. It also increased the secretion of NO, TNF-alpha, IL-10, and COX-2, and promoted the activation of transcription factor (NF-kappa B) in RAW264.7 cells. Furthermore, GYP promoted the phosphorylation of P13K and Akt in RAW264.7 cells, indicating that GYP might exert its immunoregulatory effects through modulation of PI3K/Akt pathway. Overall, the results of this study suggest that GYP can be used as a natural antioxidant and immunomodulator in the fields of functional foods.