A Comparative Study of Sodium Houttuyfonate and 2-Undecanone for Their in Vitro and in Vivo Anti-Inflammatory Activities and Stabilities

Houttuynia cordata Thunb. (H. cordata) is an anti-inflammatory herbal drug that is clinically used in Asia. The essential oil obtained from H. cordata is known to contain 2-undecanone (2-methyl nonyl ketone). In addition, sodium houttuyfonate is a compound that can be derived from H. cordata and has important clinical uses as an anti-inflammatory agent. Sodium houttuyfonate can be converted to decanoyl acetaldehyde (houttuynin) and then to 2-undecanone. Therefore, the experiments described here explore the comparative anti-inflammatory activities of these compounds. Sodium houttuyfonate showed more potent anti-inflammatory activities than that of 2-undecanone at the same dosage, both in vitro and in vivo, although both compounds significantly inhibited the production of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and the expression of toll-like receptor 4 (TLR4), but increased the secretion of interleukin-10 (IL-10) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. In addition, both compounds showed dose-dependent inhibitory effects on xylene-induced mouse ear edema. In a previous study, we found sodium houttuyfonate to be transformed to 2-undecanone during steam distillation (SD). Optimum therapeutic effects are related to the stability and pharmacological activity of the drugs. Consequently, we studied the stability of sodium houttuyfonate under a simulated gastrointestinal environment with the main influencing factors being solvent, temperature and pH effects. For the first time, sodium houttuyfonate and 2-undecanone were detected simultaneously in the mouse serum and the gastrointestinal tissue after oral administration. Sodium houttuyfonate is detected within a short period of time in the systemic circulation and tissues without conversion to 2-undecanone.