A new isomaneonene derivative from the red alga Laurencia cf. mariannensis.

Determining the structures of new natural products from marine species not only enriches our understanding of the diverse chemistry of these species, but can also lead to the discovery of compounds with novel and/or important biological activities. Herein, we describe the isolation of isomaneonene C (1), a new halogenated C15 acetogenin, and three known compounds, α-snyderol (2), cis-maneonene D (3), and isomaneonene B (4), from the organic extract obtained from the red alga Laurencia cf. mariannensis collected from Iheya Island, Okinawa, Japan. The structures of these secondary metabolites were elucidated spectroscopically. All compounds were inactive at 30 µg/disc against methicillin-resistant Staphylococcus aureus (MRSA) in combination treatment with a ß-lactam drug, meropenem.

Two New Halogenated Compounds from the Marine Red Alga Laurencia nipponica Yamada from the Kunashiri and Etorofu Islands.

The red alga Laurencia nipponica comprises various chemical races distributed relative to the ocean current in Japanese coastal areas. We investigated the chemical compositions and chemical races of L. nipponica distributed from the Kunashiri and Etorofu Islands, the confluence of the Soya warm current and Oya-shio cold current. Two new halogenated secondary metabolites, deacetylneonipponallene (1) and neopacifenol (2), along with four known compounds, deoxyprepacifenol (3), pacifenol (4), halo-chamigrene diether (5), and isolaurallene (6) were isolated from L. nipponica collected at Chikappunai, Kunashiri Island, while Zaimokuiwa (Kunashiri Island) and Sana (Etorofu Island) populations contained 3, 7-hydroxylaurene (7), 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene (8), and (3Z)-laurefucin (9). The structures of 1 and 2 were established using spectroscopic methods. The chemical races of L. nipponica distributed in this area were divided into 6- and 9-producing races. Interestingly, both races contained 4 as an additional race-index, as well as its derivatives, 2 and 5. To the best of our knowledge, this is the first example of a race comprising a mixture of two race-index compounds, suggesting that the convergence of two currents causes the production of new and diverse chemical races in this species.

Synergistic effect of secondary metabolites isolated from Pestalotiopsis sp. FKR-0115 in overcoming ß-lactam resistance in MRSA.

Six aromatic secondary metabolites, pestalone (1), emodin (2), phomopsilactone (3), pestalachlorides B (4), C (5), and D (6), were isolated from Pestalotiopsis sp. FKR-0115, a filamentous fungus collected from white moulds growing on dead branches in Minami Daito Island. The efficacy of these secondary metabolites against methicillin-resistant Staphylococcus aureus (MRSA) with and without meropenem (ß-lactam antibiotic) was evaluated using the paper disc method and broth microdilution method. The chemical structures of the isolated compounds (1-6) were characterised using spectroscopic methods, including nuclear magnetic resonance and mass spectrometry. All six isolated compounds exhibited synergistic activity with meropenem against MRSA. Among the six secondary metabolites, pestalone (1) overcame bacterial resistance in MRSA to the greatest extent.