Structures and Antibacterial Activities of Minor Dolabellanes from the Brown Alga Dilophus spiralis

Abstract

Thirteen new minor diterpenes featuring the dolabellane skeleton (1–13) were isolated from the organic extracts of the brown alga Dilophus spiralis, collected in Elafonissos Island. The structures and relative configurations of the isolated natural products were elucidated on the basis of extensive analyses of their spectroscopic data (NMR, MS, IR). The absolute configuration of 1 was determined by using the modified Mosher's method, whereas the structure of 2 was confirmed by single‐crystal X‐ray diffraction analysis. The antibacterial activities of metabolites 1–9 and 13 were evaluated against six strains of Staphylococcus aureus, including multidrug‐ and methicillin‐resistant variants. Compounds 1 and 4 exhibited noteworthy levels of activity with MIC values in the range of 2–8 μg/mL.

Diterpenes From the Marine Brown Algae of the Genus Dilophus

“…A series of dolabellane diterpenes, compounds 42 to 71, have been isolated from the brown alga D. spiralis collected on Elafonissos Island, Greece. 19,44 Moreover, compound 58 is also separated from the brown alga D. okamurai collected from the west coast of Awashima, Niigata Prefecture, Japan. 17 44 Four dolabellane diterpenes, compounds 72 to 75, are obtained from the brown alga D. mediterraneus collected from St. Paul's Bay, Malta.…”

“…19,44 Moreover, compound 58 is also separated from the brown alga D. okamurai collected from the west coast of Awashima, Niigata Prefecture, Japan. 17 44 Four dolabellane diterpenes, compounds 72 to 75, are obtained from the brown alga D. mediterraneus collected from St. Paul's Bay, Malta. 33 Three ichthyotoxic diterpenes, compounds 76 to 78, are isolated from the brown alga D. fasciola collected near Rovinj, Yugoslavia.…”

Marine Pharmacology in 2012–2013: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, and Antiviral Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

“…[40]; new butenolide cadiolides C–F ( 17 – 20 ) from a Korean tunicate Pseudodistoma antinboja [41]; novel tris-aromatic furanones cadiolides G-I ( 21 – 23 ) from the Korean dark red ascidian Synoicum sp. [42]; xanthones citreamicins θ A and B ( 24 , 25 ), isolated from the Red Sea marine Streptomyces caelestis [43]; two new aromatic polyketides, communols A and F ( 26 , 27 ), isolated from the marine Penicillium commune 518, associated with the gorgonian Muricella abnormalis [44]; two dolabellane diterpenes ( 28 , 29 ), isolated from the Greek brown alga Dilophus spiralis [45]; a novel enhygrolide A ( 30 ), isolated from the obligate marine myxobacterium Enhygromyxa salina from a mud sample from Prerow, Germany [46]; a new β-carboline alkaloid eudistomin Y 11 ( 31 ), isolated from a purple-colored ascidian Synoicum sp. [47]; a new capoamycin-type antibiotic fradimycin B ( 32 ), isolated from the marine Streptomyces fradiae strain PTZ0025 [48]; three novel cyclic bis -1,3 dialkylpyridiniums ( 33 – 35 ) from a Korean sponge Halyclona sp.…”

Antimicrobial Secondary Metabolites—Extraction, Isolation, Identification, and Bioassay

“…Kladi and coworkers [91] reported the isolation of some new C 15 eight-membered cyclic ethers with a characteristic terminal cis eneeyne moiety from the organic extract of the red alga, Laurencia glandulifera, collected at the Crete island in South Greece and found MICs in the range of 8e256 mg/mL when tested against a panel of MDR S. aureus and MRSA. Ioannou and coworkers [92] reported the isolation of 17 diterpenes featuring the dolabellane skeleton from the organic extracts of the brown alga Dilophus spiralis. Some of these revealed good antibacterial activity against six strains of S. aureus, including multidrugresistant and methicillin-resistant variants.…”