Theophylline-stimulated B16 Melanoma 4A5 Cells Research Articles

Structure-activity relationship study of 4,5-didehydroguadiscine, an aporphine alkaloid showing potent melanogenesis-inhibitory activity in B16 melanoma cells

Although 4,5-didehydroguadiscine (12a), an alkaloid with potent melanogenesis-inhibitory activity isolated from Hornschuchia obliqua (Annonaceae), consists of an aporphine nucleus with an aromatized B-ring, to date, it has not been utilized as a template for structure–activity relationship (SAR) studies of pharmacological activities because of its exceptional structure. Accordingly, herein, five analogs (12b–12f) of 12a and five benzylisoquinoline analogs (13b–13f) lacking the C11a–C11b bond of 12b–12f were prepared. The inhibitory effects of 12b–12f and 13b–13f on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were examined and compared with those of 12a. Melanogenesis-inhibitory activities of 12b–12f were the same as that of 12a, whereas the melanogenesis-inhibitory activities of 13b–13f were significantly inferior to those of 12a and 12b–12f. These results suggest that the C11a–C11b bond plays an essential role in the melanogenesis-inhibitory activities of 12a–12e.

Structural Requirements of Alkylglyceryl-l-Ascorbic Acid Derivatives for Melanogenesis Inhibitory Activity.

l-Ascorbic acid has multifunctional benefits on skin aesthetics, including inhibition of melanin production, and is widely used in cosmetics. It, however, has low stability and poor skin penetration. We hypothesize that alkylglyceryl-l-ascorbic acid derivatives, highly stable vitamin C–alkylglycerol conjugates, would have similar anti-melanogenic activity with better stability and penetration. We test 28 alkylglyceryl-l-ascorbic acid derivatives (1–28) on theophylline-stimulated B16 melanoma 4A5 cells to determine if they inhibit melanogenesis and establish any structure–function relationships. Although not the most potent inhibitors, 3-O-(2,3-dihydroxypropyl)-2-O-hexyl-l-ascorbic acid (6, IC50 = 81.4 µM) and 2-O-(2,3-dihydroxypropyl)-3-O-hexyl-l-ascorbic acid (20, IC50 = 117 µM) are deemed the best candidate derivatives based on their inhibitory activities and low toxicities. These derivatives are also found to be more stable than l-ascorbic acid and to have favorable characteristics for skin penetration. The following structural requirements for inhibitory activity of alkylglyceryl-l-ascorbic acid derivatives are also determined: (i) alkylation of glyceryl-l-ascorbic acid is essential for inhibitory activity; (ii) the 3-O-alkyl-derivatives (2–14) exhibit stronger inhibitory activity than the corresponding 2-O-alkyl-derivatives (16–28); and (iii) derivatives with longer alkyl chains have stronger inhibitory activities. Mechanistically, our studies suggest that l-ascorbic acid derivatives exert their effects by suppressing the mRNA expression of tyrosinase and tyrosine-related protein-1.

Acylated sucroses and acylated quinic acids analogs from the flower buds of Prunus mume and their inhibitory effect on melanogenesis

The methanolic extract from the flower buds of Prunus mume, cultivated in Zhejiang Province, China, showed an inhibitory effect on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. From the methanolic extract, five acylated sucroses, mumeoses A-E, and three acylated quinic acid analogs, 5-O-(E)-p-coumaroylquinic acid ethyl ester, and mumeic acid-A and its methyl ester, were isolated together with 13 known compounds. The chemical structures of the compounds were elucidated on the basis of chemical and physicochemical evidence. Inhibitory effects of the isolated compounds on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were also investigated. Acylated quinic acid analogs substantially inhibited melanogenesis. In particular, 5-O-(E)-feruloylquinic acid methyl ester exhibited a potent inhibitory effect [inhibition (%): 21.5±1.0 (P<0.01) at 0.1 μM]. Moreover, its biological effect was much stronger than that of the reference compound, arbutin [inhibition (%): 10.6±0.6 (P<0.01) at 10 μM]. Interestingly, the obtained acylated quinic acid analogs displaying melanogenesis inhibitory activity showed no cytotoxicity [cell viability >97% at 10 μM]. It is concluded that acylated quinic acid analogs are promising therapeutic agents for the treatment of skin disorders.

Melanogenesis Inhibitory and Fibroblast Proliferation Accelerating Effects of Noroleanane- and Oleanane-Type Triterpene Oligoglycosides from the Flower Buds of Camellia japonica

A 28-noroleanane-type triterpene oligoglycoside, camellioside E (4), an oleanane-type triterpene oligoglycoside, camellioside F (5), and the known compounds camelliosides A (1) and D (3) were isolated from a 50% EtOH extract of Camellia japonica flower buds from Korea. The principal constituents (1 and 5) significantly inhibited melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. Camellioside B (2), a major constituent of C. japonica grown in Japan, showed potent inhibition of melanogenesis [95.0 ± 1.0% (p < 0.01) at 20 μM]. The inhibitory effects of 1, 2, and 5 were stronger than that of the reference compound, arbutin. We believe the melanogenesis inhibitory effects of 2 and 5 are partly related to the proliferation inhibitory effects in B16 melanoma 4A5 cells. Conversely, camelliosides tended to enhance proliferation in normal human neonatal skin fibroblasts. Interestingly, camellioside B (2) significantly accelerated fibroblast proliferation. This biological selectivity could make camellioside B useful for treating skin disorders. Herein, we report the first scientific investigation of a triterpene that displays an inhibitory effect on melanogenesis, but that also has an enhancing effect on fibroblast proliferation.

Medicinal Flowers. XXXV. Nor-oleanane-type and acylated oleanane-type triterpene saponins from the flower buds of Chinese &lt;i&gt;Camellia japonica&lt;/i&gt; and their inhibitory effects on melanogenesis&lt;sup&gt;1)&lt;/sup&gt;

The methanolic extract and its 1-butanol-soluble fraction from the flower buds of Camellia japonica, cultivated in Yunnan Province, China, showed inhibitory effects on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. From the 1-butanol-soluble fraction, a new 28-nor-oleanane-type and three new oleanane-type triterpene saponins, sanchakasaponins A-D, were isolated together with four known triterpene saponins. Their chemical structures were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells and structure-activity relationships of the saponins were investigated.

Medicinal Flowers. XXXVI.&lt;sup&gt;1&lt;/sup&gt;&lt;sup&gt;)&lt;/sup&gt; Acylated Oleanane-Type Triterpene Saponins with Inhibitory Effects on Melanogenesis from the Flower Buds of Chinese &lt;i&gt;Camellia japonica&lt;/i&gt;

Four acylated oleanane-type triterpene oligoglycosides, sanchakasaponins E-H, were isolated from the flower buds of Camellia japonica cultivated in Yunnan province, China, together with four known triterpene oligoglycosides. The chemical structures of the new triterpene oligoglycosides were elucidated on the basis of chemical and physicochemical evidence. The inhibitory effects of the triterpene oligoglycoside constituents on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells were investigated.

Brazilian Natural Medicines. IV. New Noroleanane-Type Triterpene and Ecdysterone-Type Sterol Glycosides and Melanogenesis Inhibitors from the Roots of Pfaffia glomerata

The ethyl acetate and 1-butanol soluble fractions of the roots of Pfaffia glomerata were found to show inhibitory effects on melanogenesis in theophylline-stimulated B16 melanoma 4A5 cells. From the ethyl acetate and 1-butanol soluble fractions, we isolated a new noroleanane-type triterpene, pfaffianol A, its glycosides, pfaffiaglycosides A and B, and ecdysterone-type sterol glycosides, pfaffiaglycosides C, D, and E, together with eight known constituents. The structures of new constituents were determined on the basis of physicochemical and chemical evidence. Among them, pfaffianol A (IC(50)=44 microM) and pfaffoside C (IC(50)=92 microM) substantially inhibited melanogenesis without cytotoxic effects. The inhibitory effects were stronger than that of reference compound, arbutin (IC(50)=174 microM).