Nigrodiquinone A, a Hydroanthraquinone Dimer Containing a Rare C-9–C-7′ Linkage from a Zoanthid-Derived Nigrospora sp. Fungus

Abstract

One new hydroanthraquinone dimer with a rare C-9–C-7′ linkage, nigrodiquinone A (1), and four known anthraquinone monomers 2–5, were isolated from a fungus Nigrospora sp. obtained from the zoanthid Palythoa haddoni collected in the South China Sea. The structure of 1 was established through extensive NMR spectroscopy, and the absolute configuration was elucidated by comparing computed electronic circular dichroism (ECD) and optical rotations (OR) with experimental results. All the compounds were evaluated for antiviral activity, and 1 was also evaluated for antibacterial activity. Compound 4 displayed mild antiviral activity against coxsackie virus (Cox-B3) with the IC50 value of 93.7 μM, and 5 showed an IC50 value of 74.0 μM against respiratory syncytial virus (RSV).

Total Synthesis of (+)-Rubellin C

“…Anthraquinone-based natural products have provided a variety of medicinally valuable entities, including FDA-approved therapies such as the chemotherapeutic anthracyclines, the chemotherapeutic and immunosuppressant mitoxantrone for multiple sclerosis, the laxative sennosides, and the anti-inflammatory diacerein for osteoarthritis . A large number of naturally occurring anthraquinoids are characterized by homodimeric linkages . Fewer family members are characterized by heterodimeric structures that contain anthraquinones linked by multiple bonds to other anthraquinone or xanthone partners; these natural products have inspired elegant syntheses to access their molecular architectures …”

Anthraquinones and Their Analogues from Marine-Derived Fungi: Chemistry and Biological Activities

“…8-acetoxyaustrocortirubin ( 47a ), 8-acetoxy-3,5-dihydroxy-7-methoxy-2-methylanthracene-9,10-dione ( 58a ), 5-acetoxy-3,8-dihydroxy-7-methoxy-2-methylanthracene-9,10-dione ( 58b ), 3-acetoxy-5,8-dihydroxy-7-methoxy-2-methylanthracene-9,10-dione ( 58c ), 5,8-diacetoxy-3-hydroxy-7-methoxy-2-methylanthracene-9,10-dione ( 58d ), 3,8-diacetoxy-5-hydroxy-7-methoxy-2-methylanthracene-9,10-dione ( 58e ), 3,5-diacetoxy-8-hydroxy-7-methoxy-2-methylanthracene-9,10-dione ( 58f ), and 3,5,8-triacetoxy-7-methoxy-2-methylanthracene-9,10-dione ( 58g ) ( Figure 5 ) [ 68 ]. The fermentation extract of the same fungus, isolated from the inner tissue of the zoathid, Palythoa haddoni (GX-WZ-20100026), collected from coral reefs in the South China Sea, also furnished both 47 and 58 ( Figure 5 ) [ 69 ].…”

“…The absolute configurations of the stereogenic carbons in 187 were tentatively assigned as 2 S ,3 R ,4 S on the ground that 187 shared a biogenesis with 4a- epi -9α-methoxydihydrodeoxybostrycin whose absolute structure had already been established [ 68 ]. Compound 187 was also reported from the same fungal strain but was isolated from the inner tissue of the zoathid, Palythoa haddoni [ 69 ]. A bostrycin derivative, hydroxybostrycin ( 188 ) ( Figure 16 ), was isolated from the culture broth extract of a mangrove endophytic fungus, Altenaria sp.…”

“…The relative configurations of the stereogenic carbons of 251 were assigned as 1a R* ,2 S* ,3 R* ,4a R* ,9 R* ,2′ S* ,3′ R* ,4′ S* , which were the same as those of 4a- epi -9α-methoxydihydrodeoxybostrycin ( 210 ) and 10-deoxybostrycin ( 187 ). The absolute configurations of the stereogenic carbons of 251 were established as 1a R ,2 S ,3 R ,4a R ,9 R ,2′ S ,3′ R ,4′ S by comparison of the calculated and experimental ECD spectra as well as of the values of the calculated and experimental optical rotations [ 69 ].…”

“…Compound 47 exhibited antiviral activity against respiratory syncytial virus (RSV) with an IC 50 value of 74.0 μM, while 58 showed a moderate inhibitory activity against coxsackie virus (Cox-B3) with an IC 50 value of 93.7 μM. The positive control, ribavirin, showed antiviral activity against RSV and Cox-B3 with IC 50 values of 78.0 and 39.0 μM, respectively [ 69 ].…”