In this study, we investigated the anti-inflammatory effect of rosmarinic acid methyl ester (RAME) isolated from a mutant cultivar of Perilla frutescens (L.) Britton. We found that RAME inhibits lipopolysaccharide (LPS)-induced nitric oxide (NO) production, with an IC₅₀ of 14.25 µM, in RAW 264.7 cells. RAME inhibited the LPS-induced expression of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, IL-10, monocyte chemoattractant protein-1, interferon-β, and inducible nitric oxide synthase (iNOS). Moreover, RAME suppressed the activation of nuclear factor kappa B. These results suggest that the downregulation of iNOS expression by RAME was due to myeloid differentiation primary response gene 88 (MyD88)-dependent and -independent pathways. Furthermore, RAME induced the expression of heme oxygenase-1 (HO-1) through activation of nuclear factor-erythroid 2-related factor 2. Treatment with tin protoporphyrin, an inhibitor of HO-1, reversed the RAME-induced suppression of NO production. Taken together, RAME isolated from P. frutescens inhibited NO production in LPS-treated RAW 264.7 cells through simultaneous induction of HO-1 and inhibition of MyD88-dependent and -independent pathways.

The leaves of Perilla frutescens var. crispa (Lamiaceae)—known as ‘Jureum-soyeop’ or ‘Cha-jo-ki’ in Korean, ‘ZI SU YE’ in Chinese, and ‘Shiso’ in Japan—has been used as a medicinal herb. Recent gamma irradiated mutation breeding on P. frutescens var. crispa in our research group resulted in the development of a new perilla cultivar, P. frutescens var. crispa (cv. Antisperill; PFCA), which has a higher content of isoegomaketone. The leaves of PFCA were extracted by supercritical carbon dioxide (SC-CO₂) extraction, and phytochemical investigation on this extract led to the isolation and identification of a new compound, 9-hydroxy-isoegomaketone [(2E)-1-(3-furanyl)-4-hydroxy-4-methyl-2-penten-1-one; 1]. Compound 1 exhibited inhibitory activity on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW264.7 cells with an IC₅₀ value of 14.4 μM. The compounds in the SC-CO₂ extracts of the radiation mutant cultivar and the original plant were quantified by high-performance liquid chromatography with diode array detection.

In this study, we attempted to identify and assess effects of isoegomaketone (IK) isolated from Perilla frutescens var. crispa on the development of rheumatoid arthritis (RA). RA was induced in male Balb/c mice by collagen antibody injection. Experimental animals were randomly divided into five groups: normal, collagen antibody-induced arthritis (CAIA), CAIA + IK (5 mg/kg/day), CAIA + IK (10 mg/kg/day), and CAIA + apigenin (16 mg/kg/day) and respective treatments were administered via oral gavage once per day for four days. Mice treated with IK (10 mg/kg/day) developed less severe arthritis than the control CAIA mice. Arthritic score, paw volume, and paw thickness were less significant compared to the control CAIA mice at day seven (73%, 15%, and 14% lower, respectively). Furthermore, histopathological examination of ankle for inflammation showed that infiltration of inflammatory cells and edema formation were reduced by IK treatment. Similarly, neutrophil to lymphocyte ratio (NLR) in whole blood was lower in mice treated with IK (10 mg/kg/day) by 85% when compared to CAIA mice. Taken together, treatment with IK delays the onset of the arthritis and alleviates the manifestations of arthritis in CAIA mice.

In this study, we aimed to compare supercritical carbon dioxide extraction and ethanol extraction for isoegomaketone (IK) content in perilla leaf extracts and to identify the optimal method. We measured the IK concentration using HPLC and inflammatory mediators in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells from the extracts. The IK concentration was 10-fold higher in perilla leaf extracts by supercritical carbon dioxide extraction (SFE) compared with that in perilla leaf extracts by ethanol extraction (EE). When the extracts were treated in LPS-induced RAW 264.7 cells at 25 μg/mL, the SFE inhibited the expression of inflammatory mediators such as nitric oxide (NO), monocyte chemoattractant protein-1 (MCP-1), interleutkin-6 (IL-6), interferon-β (IFN-β), and inducible nitric oxide synthase (iNOS) to a much greater extent compared with EE. Taken together, supercritical carbon dioxide extraction is considered the optimal process for obtaining high IK content and anti-inflammatory activities in leaf extracts from the P. frutescens Britt. radiation mutant.