Abstract
Two new bromotyrosine alkaloids, ceratinadins E (1) and F (2), were isolated from an Okinawan marine sponge Pseudoceratina sp. as well as a known bromotyrosine alkaloid, psammaplysin F (3). The gross structures of 1 and 2 were elucidated on the basis of spectroscopic data. The absolute configurations of 1 and 2 were assigned by comparison of the NMR and ECD data with those of a known related bromotyrosine alkaloid, psammaplysin A (4). Ceratinadins E (1) and F (2) are new bromotyrosine alkaloids possessing an 8,10-dibromo-9-methoxy-1,6-dioxa-2-azaspiro[4.6]undeca-2,7,9-trien-4-ol unit with two or three 11-N-methylmoloka’iamine units connected by carbonyl groups, respectively. Ceratinadin E (1) exhibited antimalarial activities against a drug-resistant and a drug-sensitive strains of Plasmodium falciparum (K1 and FCR3 strains, respectively).
Highlights
According to the World Health Organization (WHO), 216 million clinical cases of malaria occurred and 445,000 people died of malaria in 2016 [1]
Structure elucidation, and structure-activity relationship studies of this type of alkaloids are required for the development of new antimalarial drugs
Summary
According to the World Health Organization (WHO), 216 million clinical cases of malaria occurred and 445,000 people died of malaria in 2016 [1]. The representative antimalarial natural products, quinine and artemisinin, and their derivatives have been widely used for the treatment of malaria. Marine sponges have been recognized as a rich source of unique bioactive natural products. A variety of bromotyrosine alkaloids with a wide range of biological activities have been isolated from marine Verongid sponges [2] and references therein. The bromotyrosine alkaloids possessing the 1,6-dioxa-2-azaspiro[4.6]undecane skeleton, such as pammaplysins F (3), G, and H, and 19-hydroxypsammaplysin E, have been reported to exhibit antimalarial activity [3,4,5,6] Notably, psammaplysins F (3) and G showed antimalarial activities against the drug-sensitive strain and against the drug-resistant strain of Plasmodium falciparum [4]
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