Alkaloids of Linderae Radix suppressed the lipopolysaccharide-induced expression of cytokines in cultured macrophage RAW 264.7 cells

Linderae Radix, the dry roots of Lindera aggregata (Sims) Kosterm, has long been used as traditional Chinese medicine for treatment of inflammatory diseases. The total alkaloids are believed to be the active components responsible for anti-inflammation of Linderae Radix. Here, the total alkaloids of Linderae Radix were extracted and isolated, including 12 isoquinoline alkaloids and 1 furan sesquiterpene. Within the alkaloids, norisoboldine, boldine, linderaline, isoboldine, reticuline, N-methyllaurotetanine, norjuziphine were found to be the major ingredients. In lipopolysaccharide-treated macrophage RAW 264.7 cells, application of Linderae Radix extract, or total alkaloids, suppressed the transcription of proinflammatory cytokines, interleukin-1β and interleukin-6. Out of the 12 alkaloids, norisoboldine, boldine, and isoboldine were tested in lipopolysaccharide-treated macrophages, and norisoboldine was the strongest alkaloid in suppressing the cytokine expressions. The current studies suggested that the identification of alkaloids from Linderae Radix could provide a plausible explanation for herbal therapeutic functions.