Anti-Cancer - The intake of citrus fruits has been suggested as a way to prevent the development of some types of human cancer. Nitric oxide (NO) is closely associated with the processes of epithelial carcinogenesis. We attempted a search for NO generation inhibitors in Citrus unshiu.

As a result, nobiletin, a polymethoxyflavonoid, was identified as an inhibitor of both NO and O₂⁻ generation. Nobiletin significantly inhibited two distinct stages of skin inflammation induced by double TPA application [first stage priming (leukocyte infiltration) and second stage activation (oxidative insult by leukocytes)] by decreasing the inflammatory parameters.

The present study suggests that nobiletin is a functionally novel and possible chemopreventive agent in inflammation-associated tumorigenesis.

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Anti-Inflammatory - In this paper, they further examine the effects of nobiletin on the production of cyclooxygenases (COXs), prostaglandin (PG) E₂, and proinflammatory cytokines in human synovial fibroblasts and the mouse macrophage J774A.1 cell line. Nobiletin suppressed the interleukin (IL)-1-induced production of PGE₂ in human synovial cells in a dose-dependent manner (<64 μM). Additionally, it selectively downregulated COX-2, but not COX-1 mRNA expression.

These anti-inflammatory actions of nobiletin are very similar to those of anti-inflammatory steroids such as dexamethasone, and the upregulation of TIMP-1 production is a unique action of nobiletin.

Therefore, these results further support the notion that nobiletin is likely to be a candidate for characterization as a novel immunomodulatory and anti-inflammatory drug.

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Apoptotic Effect - Lung cancer is the leading cause for cancer-related death worldwide and the effectiveness of current treatments is very limited. Here we reported that Nobiletin, an effective component of citrus fruit, has antiproliferative activity on lung cancer cells both in vitro and in vivo.

Cell viability and clonogenic assay showed that Nobiletin dose-dependently suppressed the proliferation of human lung adenocarcinoma cell line A549 cells, while has having a minimal effect on human umbilical vein endothelial cell line ECV-304 cells.

Furthermore, Nobiletin had overt inhibitory effect on the tumor growth in nude mice model was observed in vivo. Taken together, these results suggest that Nobiletin could induce p53-mediated cell cycle arrest and apoptosis via modulated the Bax:Bcl-2 protein ratio, is effective as a potent antitumor agent on lung tumors.

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Eliminate Acne - Acne vulgaris is characterized by excess sebum production, and apart from all-trans retinoic acid (atRA) or 13-cis retinoic acid (13-cisRA), there are few effective agents for acne therapy that directly suppresses sebaceous lipogenesis. In this study, we demonstrated that topical application of a citrus polymethoxy flavonoid, nobiletin, to hamster auricles decreased skin surface triacylglycerols (TG) level and the size of sebaceous glands along with inhibition of diacylglycerol acyltransferase (DGAT)-dependent TG synthesis and sebocyte proliferation. The inhibitory actions were similar to that observed with atRA and 13-cisRA in hamster sebocytes. The antilipogenic and antiproliferative actions of nobiletin were also reproduced in UVB (5.4kJ/m2)-irradiated hamsters, which showed aberrant enhancement of sebum accumulation and sebaceous enlargement.

Furthermore, nobiletin, but not 13-cisRA, augmented sebum excretion along with increases in intracellular cAMP level, protein kinase A (PKA) activation, and apoptosis-independent phosphatidylserine (PS) externaliza- tion in cell membrane. These phenomena were reproduced by forskolin and inhibited by a PKA inhibitor, H-89. These results provide early evidence that nobiletin is an effective candidate for acne therapy through mechanisms that include the inhibition of DGAT-dependent TG synthesis and sebocyte proliferation, and the progression of apoptosis-independent and PS-externalization-dependent sebum excretion by PKA activation.

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