Maclurin inhibits caspase-11 non-canonical inflammasome in macrophages and ameliorates acute lethal sepsis in mice.

Maclurin is a natural phenolic compound isolated from Morus alba(white mulberry) andGarcinia mangostana (purple mangosteen) and has been reported to regulate cancer progression, oxidative stress, and melanogenesis. The regulatory role of maclurin, however, has never been demonstrated. This study investigated in vitro and in vivo anti-inflammatory roles of maclurin and the underlying mechanism in caspase-11 non-canonical inflammasome-stimulated inflammatory responses in macrophages and an animal model of acute lethal sepsis. Maclurin protected J774A.1 macrophages from LPS-induced cytotoxicity and suppressed caspase-11 non-canonical inflammasome-stimulated pyroptosis. Maclurin decreased the secretion and mRNA expression of pro-inflammatory cytokines and inflammatory mediators, such as IL-1ß, IL-18, TNF-α, IL-6, nitric oxide (NO), and inducible NO synthase (iNOS) in caspase-11 non-canonical inflammasome-stimulated J774A.1 macrophages. Mechanistic studies revealed that maclurin markedly suppressed the proteolytic activation of caspase-11 and gasdermin D (GSDMD) in caspase-11 non-canonical inflammasome-stimulated J774A.1 macrophages, while it did not inhibit caspase-11-mediated direct sensing of LPS. In vivo study revealed that maclurin ameliorated acute lethal sepsis in mice by increasing the survival rate and decreasing the serum levels of IL-1ß and IL-18 without significant toxicity. In conclusion, this study suggests that maclurin is a novel anti-inflammatory agent in inflammatory responses and against acute lethal sepsis via the inhibition of the caspase-11 non-canonical inflammasome in macrophages, which justifies its potential as an anti-inflammatory therapeutic agent in traditional medicine.

Xanthone-related compounds as an anti-browning and antioxidant food additive.

Although enzymatic browning is important for the beneficial coloration of some foods, it also causes negative effects on safety, quality, and nutritional values of fruit and vegetable. Thus, anti-browning natural compounds have gained attention in the food industry. Xanthone-related compounds have been well-known for its biological activities, but their roles in enzymatic browning are unclear. We screened xanthone-related natural compounds for their anti-polyphenol oxidase (PPO) activity and maclurin was selected for further experiments due to stronger PPO-inhibitory activity. Maclurin suppressed enzymatic browning in potato supernatant for long-term partly through direct binding to and inactivating PPO presumably by forming multiple hydrogen bonds and aromatic interactions with the binding pocket. In addition, maclurin elevated antioxidant capacity when added to potato supernatant. Considering the diverse health-promoting effects of antioxidants, maclurin can be applied as a functional food additive to block enzymatic browning and increase the antioxidant property of foods including beverages and soups.

Maclurin exerts anti-cancer effects on PC3 human prostate cancer cells via activation of p38 and inhibitions of JNK, FAK, AKT, and c-Myc signaling pathways.

Maclurin is a phenolic compound extracted from purple mangosteen and mulberry twigs. Earlier reports indicated that it exerts antioxidant activity. We hypothesized that maclurin exerts antioxidant activity and anti-cancer effects in small cell neuroendocrine carcinomas (SCNCs), a very aggressive type of human prostate cancer. To verify our hypothesis, we selected PC3 cells as a model system and investigated the antioxidant activity and anti-cancer effects of maclurin. In the reactive oxygen species (ROS) detection assay for the verification of antioxidant activity, we observed the unexpected prooxidant activity of maclurin in PC3 cells. For the anti-cancer activities, we investigated the effects of maclurin on induction of apoptosis and inhibition of metastatic characteristics of PC3 cells. In the apoptosis assay, maclurin significantly induced apoptosis of PC3 cells. Maclurin also showed significant anti-metastatic effects. Maclurin inhibited cell migration in a dosage-dependent manner. In addition, the gelatin zymography assay indicated that maclurin inhibited activities of matrix metalloproteinase-2 and 9 (MMP-2 and MMP-9) that affect cell migration and extracellular matrix (ECM) degradation. Then, we investigated the effects of maclurin on the cancer-related signaling molecules. Maclurin activated p38 signaling and inhibited c-Jun N-terminal kinase (JNK), focal-adhesion kinase (FAK), AKT, and c-Myc signalings in PC3 cells. Finally, we observed prooxidant activity and anti-SCNC effects of maclurin in DU145 cells. This suggests that the effects of maclurin may not be specifically limited to PC3 cells. Our findings suggest that maclurin exerts anti-cancer effects on SCNC cells via activation of p38 and inhibitions of JNK, FAK, AKT and c-Myc signalings.