Alkaloid constituents from flower buds and leaves of sacred lotus (Nelumbo nucifera,Nymphaeaceae) with melanogenesis inhibitory activity in B16 melanoma cells |
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| Authors: | Seikou Nakamura Souichi Nakashima Genzo Tanabe Yoshimi Oda Nami Yokota Katsuyoshi Fujimoto Takahiro Matsumoto Rika Sakuma Tomoe Ohta Keiko Ogawa Shino Nishida Hisako Miki Hisashi Matsuda Osamu Muraoka Masayuki Yoshikawa |
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| Affiliation: | 1. Department of Pharmacognosy, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan;2. School of Pharmacy, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan |
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| Abstract: | Methanolic extracts from the flower buds and leaves of sacred lotus (Nelumbo nucifera, Nymphaeaceae) were found to show inhibitory effects on melanogenesis in theophylline-stimulated murine B16 melanoma 4A5 cells. From the methanolic extracts, a new alkaloid, N-methylasimilobine N-oxide, was isolated together with eleven benzylisoquinoline alkaloids. The absolute stereostructure of the new alkaloid was determined from chemical and physicochemical evidence. Among the constituents isolated, nuciferine, N-methylasimilobine, (?)-lirinidine, and 2-hydroxy-1-methoxy-6a,7-dehydroaporphine showed potent inhibition of melanogenesis. Comparison of the inhibitory activities of synthetic related alkaloids facilitated characterization of the structure-activity relationships of aporphine- and benzylisoquinoline-type alkaloids. In addition, 3–30 μM nuciferine and N-methylasimilobine inhibited the expression of tyrosinase mRNA, 3–30 μM N-methylasimilobine inhibited the expression of TRP-1 mRNA, and 10–30 μM nuciferine inhibited the expression of TRP-2 mRNA. |
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