Inhibitory effects of cranberry polyphenol and volatile extracts on nitric oxide production in LPS activated RAW 264.7 macrophages†
Cranberry volatiles have received little attention for health-promoting properties. In this study, we compared the inhibitory effects of cranberry polyphenol and volatile extracts and volatile standards on nitric oxide (NO) production in lipopolysaccharide (LPS) activated RAW 264.7 macrophages. Polyphenols were analyzed by HPLC/HPLC-MS and volatiles were analyzed by GC/GC-MS. The inhibition of NO production of the fresh cranberry polyphenol and volatile extracts and α-terpineol, linalool, linalool oxide, and eucalyptol standards at 2, 4, and 8-fold dilutions of their original concentrations in fresh cranberries was evaluated by treating these extracts/standards for 1 h before or after LPS application for 24 h. After inducing inflammation with LPS, the polyphenol treatments (317.8 and 635.7 μg g−1) and 1.8 μg g−1 volatile treatment lowered NO levels 46–62% compared to the positive control (P < 0.05). When the cells were treated with polyphenol and volatile extracts before inducing inflammation, the 635.7 μg g−1 and 317.8 μg g−1 polyphenol treatments and 1.8 μg g−1 and 0.9 μg g−1 volatile treatments lowered NO levels (13–52%) compared to the positive control (P < 0.05). Polyphenol and volatile extracts from cranberry were effective in reducing NO production whether applied before or after the application of LPS. α-Terpineol at a concentration found in fresh cranberries (1.16 μg mL−1) was also found to be effective in reducing NO production whether cells were treated before or after application of LPS. Future studies are needed to reveal the mechanisms by which volatile compounds, especially α-terpineol act to mitigate inflammation and to determine the bioavailability of terpenes.