A potential natural melanogenesis inhibitor was discovered in the form of a sesquiterpene isolated from the flowers of Inula britannica, specifically 6-O-isobutyrylbritannilactone (IBL). We evaluated the antimelanogenesis effects of IBL on B16F10 melanocytes and zebrafish embryos. As a result, we found that 3-isobutyl-1-methylxanthine (IBMX)-induced melanin production was reduced in a dose-dependent manner in B16F10 cells by IBL. We also analyzed B16F10 cells that were and were not treated with IBMX, investigating the melanin concentration, tyrosinase activity, mRNA levels. We also studied the protein expressions of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related proteins (TRP1, and TRP2). Furthermore, we found that melanin synthesis and tyrosinase expression were also inhibited by IBL through the modulation of the following signaling pathways: ERK, phosphoinositide 3-kinase (PI3K)/AKT, and CREB. In addition, we studied antimelanogenic activity using zebrafish embryos and found that the embryos had significantly reduced pigmentation in the IBL-treated specimens compared to the untreated controls.

2α-Hydroxyeudesma-4,11(13)-dien-8β,12-olide (HEDO), a eudesmane-type sesquiterpene lactone belonging to large group of plant terpenoids isolated from Inula britannica, displays cytotoxic activity against diffuse large B cell lymphoma cells in vitro. However, the molecular mechanism of the anticancer effect remains unclear. In this study, we showed that HEDO inhibits cell growth by inducing apoptosis in lymphoma cell lines through its antiproliferative activity. HEDO increases the depolarization of mitochondrial membrane potential and upregulated intracellular reactive oxygen species (ROS). Furthermore, we examined the cell cycle effect, and our results provided evidence that the arrest of the cell cycle at the SubG0/G1 phase plays an important role in the ability of HEDO to inhibit cell growth in Ontario Cancer Institute (OCI)-LY3 lymphoma cells by preventing nuclear factor-kappa B (NF-κB) signaling. In addition, HEDO induced apoptosis by instigating the activation of Bcl-2-associated X (BAX) and cleaved caspase-3, decreasing B-cell lymphoma 2 (BCL2), B-cell lymphoma-extra large (BCL-XL), and procaspase 3 expression levels. Based on these findings, we suggest that HEDO has potential as an anticancer drug of lymphoma by inducing ROS-dependent accumulation of SubG0/G1 arrest and apoptosis in OCI-LY3 cells.

Melanogenesis is a complex process by which melanin is produced by melanocytes in melanosomes [1]. Melanin is responsible for skin, hair, and eye color and plays a critical role in protecting the skin against ultraviolet radiation [2]. However, excessive melanin synthesis and accumulation are associated with hyperpigmentation disorders including freckles, melasma, and senile lentigo [3]. Regulation of melanin production is therapeutically important when treating pigmentation-related disorders. Several synthetic antimelanogenic agents are known; however, only a few are used as skin-whitening agents because of various safety issues [4]. There is an increasing need for natural melanogenesis inhibitors with fewer side effects, for cosmetic and medicinal applications [5].Inula britannica Linnaeus (Asteraceae) is well known in China ("Xuan-Fu-Hua"), as its flowers are used in traditional Chinese medicine to treat digestive disorders, bronchitis, and inflammation [6]. In a preliminary screen using B16F10 melanoma cells, we found that a flower extract of I. britannica significantly reduced melanin production [7]. However, the active principle remained unclear. Further study of I. britannica flowers yielded a new sesquiterpene, inularin. Here, we describe its isolation and structural characterization, its antimelanogenic effect in B16F10 cells, and its effect on melanin production by embryonic zebrafish.An ethanol extract of I. britannica flowers was subjected to silica gel column chromatography and divided into four fractions (A-D) based on thin-layer chromatography (TLC) data. Fraction C, which significantly reduced melanin production (65% inhibition at 50 μg/ml) by B16F10 cells, was subjected to a further series of chromatographic separation steps guided by antimelanogenic activity, leading to isolation of inularin (Fig. 1A). The material was an amorphous white powder with a molecular ion peak at m/z 349.1626 [M + Na] + on highresolution electron ionization mass spectrometry (HRESIMS), corresponding to a molecular formula of C 17 H 26 O 6 . The 1 H-NMR spectrum displayed the characteristic signals of paired olefinic protons at δ H 6.28 (1H, s) and 5.68 (1H, s), two oxygenated methine protons at δ H 5.29 (1H, m) and 3.28 (1H, dd, J = 10.4, 4.8 Hz), two singlet methyls at δ H 1.17 (3H, s) and 1.03 (3H, s), and an acetoxymethyl at δ H 1.95 (3H, s) (Table 1). The 13 C-NMR spectrum (Table 1), combined with the distortionless enhancement by polarization transfer (DEPT) data, yielded 17 carbon signals consisting of three methyls, five methylenes, four methines, three quaternary carbons, and two carbonyl carbons; the signals at δ C 172.2 and 21.2 were assigned to an acetoxy group. These spectroscopic data suggest that inularin is a eudesmane-type sesquiterpene with an acetoxy moiety, as are its analogs [8]. A complete assignment of the chemical shifts of inularin and its substitution pattern was made using various 2D-NMR techniques. The 1 H-1 H correlation spectroscopy (COSY) correlations of inularin established two segments: ...