In Vitro and In Vivo Anti-Inflammatory Activities of Benjakul: A Potential Medicinal Product from Thai Traditional Medicine

Benjakul (BJK) is a Thai traditional remedy consisting of five plants: Piper chaba Hunt., Piper sarmentosum Roxb., Piper interruptum Opiz., Plumbago indica Linn., and Zingiber officinale Roscoe. It is used as a first-line drug to balance patient's symptoms before other treatments. BJK ethanolic extract has been reported to show anti-inflammatory activity through various mediators, e.g., nitric oxide, TNF-α, IL-1β, and IL-6. Therefore, BJK could serve as a potential novel anti-inflammatory herbal medicine. However, studies on prostaglandin E2 (PGE2), one of the key mediators in acute inflammation, and anti-inflammation in animal models (in vivo) have not been done. This study investigated the anti-inflammatory activity of BJK extract and some of its chemical compounds against PGE2 production in murine macrophage (RAW 264.7) cell line and two in vivo models of anti-inflammatory studies. Ethanolic extract of BJK (BJK[E]) showed high inhibitory activity against PGE2 production with an IC₅₀ value of 5.82 ± 0.10 μg/mL but its water extract (BJK[W]) was inactive. Two chemicals from BJK[E], i.e., plumbagin and myristicin, which served as biological markers, showed strong activity with IC₅₀ values of 0.08 ± 0.01 and 1.80 ± 0.06 μg/mL, respectively. BJK[E] was administered both topically and orally to rats inhibited with inflammation induced by ethyl phenylpropiolate (rat ear edema model) and carrageenan (hind paw edema model). Moreover, the biological activity of BJK extract did not reduce after six-month storage under accelerated condition (40°C, 75% RH). This indicated its stability and a 24-month shelf-life under normal condition. These results supported not only the use of BJK in Thai traditional medicine but also the possibility of further development of phytopharmaceutical products from BJK.