Assessment of Anti-Inflammatory and Antioxidant Effects of Citrus unshiu Peel (CUP) Flavonoids on LPS-Stimulated RAW 264.7 Cells

Citrus unshiu is a popular medicinal herb in several Asian countries, in particular South Korea. C. unshiu peel (CUP) has several biologically active compounds, including flavonoids. Hence, this research aimed to label the flavonoids from CUP by HPLC-MS/MS analysis and examine their anti-inflammatory and antioxidant potential on LPS-stimulated RAW 264.7 macrophages. A total of four flavonoids (Rutin, naringin, hesperidin, and poncirin) were characterized, and their contents were quantified from CUP. It showed that the naringin is rich in CUP. Further, treatment with the flavonoids at concentrations of 2.5 and 5 μg/mL had no effect on the cell viability of RAW 264.7 macrophages. On the other hand, it decreased the production and expression of inflammatory mediators and pro-inflammatory cytokines such as NO, PGE2, TNF-α, IL-1β, iNOS, and COX2 in the LPS-stimulated RAW 264.7 macrophages. In addition, flavonoids treatment inhibited the NF-κB activation by downregulating the p-p65 and p-IκBα proteins expression. Furthermore, reactive oxygen species (ROS) production considerably decreased at the same concentrations while antioxidant enzyme activity increased in the LPS-stimulated RAW 264.7 macrophages. Collectively, our results show that CUP flavonoids have the potential to decrease inflammation and oxidative damage.

Comparison of the Effects of Yokukansan and Yokukansankachimpihange on Glutamate Uptake by Cultured Astrocytes and Glutamate-Induced Excitotoxicity in Cultured PC12 Cells

The traditional Japanese Kampo medicine yokukansan (YKS) is effective for behavioral and psychological symptoms of dementia (BPSD) in patients with Alzheimer’s disease. As the pharmacological mechanisms, YKS is known to protect astrocytes from thiamine-deficiency (TD)-induced decreased glutamate (Glu) uptake and neuron model cells (PC 12 cells) from Glu-induced death. Yokukansankachimpihange (YKSCH) is an alternative formula to YKS, in which Citrus unshiu peel and Pinellia tuber are added to the YKS components, and is sometimes used to treat BPSD, but its pharmacological properties remain unknown. This study aims to investigate the cellular pharmacological effects of YKS and YKSCH on glutamatergic pathways, compare their efficacy, and determine the differences and similarities in the activities between these formulations. First, we examined the effects of YKS and YKSCH on Glu uptake by cultured astrocytes under TD conditions. We observed significant ameliorative effects of YKS and YKSCH on the TD-induced decrease in Glu uptake, with a 50% effective dose of 8.9 ± 1.8 μg/mL and 45.3 ± 9.2 μg/mL, respectively. Second, using cultured PC12 cells as a model for neurons, we examined the effects of YKS and YKSCH on Glu-induced cell death. We observed that YKS and YKSCH had significant inhibitory effects on Glu-induced cell death, with a 30% effective dose of 51.4 ± 20.8 μg/mL and 49.2 ± 11.0 μg/mL, respectively. Thus, while YKSCH was less effective than YKS in ameliorating the TD-induced decrease in Glu uptake by astrocytes, the two drugs showed similar inhibitory effects on Glu-induced PC12 cell death. These findings are important for understanding the differences and similarities in pharmacological actions between these drugs.

Co-Existence of Hypertensive and Anti-Hypertensive Constituents, Synephrine, and Nobiletin in Citrus unshiu Peel

A single herb can contain multiple constituents with diverse bioactivities. We found that the extract of Citrus unshiu peel (CUP), induced abnormal vasoconstriction responses on the freshly isolated rat aortic rings in vitro. CUP stimulated the vasoconstriction alone, and it suppressed the phenylephrine-stimulated vasoconstriction. We studied the reasons behind this abnormal vasoconstriction pattern. Major constituents of CUP were determined and evaluated for their vaso-activities. Notably, synephrine, a contractile agonist, and nobiletin, newly identified to have anti-contractile activity co-existed in CUP. Synephrine and nobiletin competitively blocked or activated the same contractile targets resulting in contradicting and abnormal vasoconstriction responses. Accordingly, the vasoconstriction pattern varies significantly depending on the relative contents of synephrine and nobiletin in CUP. Interestingly, this response pattern could be observed with another plant extract, Acorus gramineus Sol. Collectively, we demonstrated that active ingredients with contradicting bioactivities could co-exist in a single plant extract, interact and produce abnormal response patterns in bioassay, which would give an important insight into the interpretation of unusual activity patterns induced by plant extracts.