Naphthoquinone-Based Meroterpenoids from Marine-Derived Streptomyces sp. B9173

Abstract

Naphthoquinone-based meroterpenoids are hybrid polyketide-terpenoid natural products with chemical diversity and a broad range of biological activities. Here, we report the isolation of a group of naphthoquinone-containing compounds from Streptomyces sp. B9173, and their structures were elucidated by using a combination of spectroscopic techniques, including 1D, 2D NMR, and high-resolution mass (HRMS) analysis. Seven flaviogeranin congeners or intermediates, three of which were new, have been derived from common naphthoquinone backbone and subsequent oxidation, methylation, prenylation, and amino group incorporation. Both flaviogeranin B1 (1) and B (2) contain an amino group which was incorporated into the C8 of 1,3,6,8-terhydroxynaphthalene (THN). Flaviogeranin D (3) contains an intact C-geranylgeranyl residue attached to the C2 of THN, while the O-geranylgeranyl group of 2 links with the hydroxyl on the C2 site of THN. Four compounds were selected and tested for antibacterial activity and cytotoxicity, with 3 and flaviogeranin C2 (5) displaying potent activity against selected bacteria and cancer cell lines. In light of the structure features of isolated compounds and the biosynthetic genes, a biosynthetic pathway of naphthoquinone-based flaviogeranins has been proposed. These isolated compounds not only extend the structural diversity but also represent new insights into the biosynthesis of naphthoquinone-based meroterpenoids.

Meroterpenoids: A Comprehensive Update Insight on Structural Diversity and Biology

“…Notably, compound 381 illustrated significant antibacterial effects towards Mycobacterium smegmatis and Staphylococcus aureus with MIC values ranging from 5.2 to 9.2 µg/mL. In addition, compound 381 also possessed potent cytotoxic effects towards HeLa and A549 with IC 50 : 0.4 and 0.6 µM, respectively [120]. In another report Streptomyces sp.…”

“…This compound exhibited moderate cytotoxic effects on B16, MDA-MB-321, and A549 cells with IC 50 ranging from 21.5 to 41.5 µM [55]. Phloroglucinol based meroterpenes named fischernolides A-D (119)(120)(121)(122), having a diterpene core (Figure 13), were produced by Euphorbia fischeriana. Meroterpenes 120 and 122 illustrated significant cytotoxic effects towards HT-29, Bel-7402, MCF-7, A549, and HeLa with IC 50 values from 2.0 to 8.6 µM [56].…”

Natural Quinone Dyes: A Review on Structure, Extraction Techniques, Analysis and Application Potential

“…In bacteria, quinones such as 2-hydroxy-9,10-anthraquinone and naphthoquinone have been isolated from Streptomyces olivochromogenes [56] and Streptomyces sp. [57], respectively. In.algae, 2,6-dichloro-1,4-benzoquinone has been found in green algae [58], 1,4-napthoquinone in brown algae [59] and 1-methyl emodin anthraquinone in red algae among others.…”

Recently Discovered Secondary Metabolites from Streptomyces Species

“…CA-271078: one each of types A (28) and C (31), and two of which were type B napyradiomycins (29 and From a group of six compounds isolated from Streptomyces sp. MJM3055 and spectroscopically characterised, two compounds, (3E,8E)-1-hydroxydeca-3,8-dien-5-one ( 24) and (S,E)-3-hydroxy-5-oxodec-8-en-1-yl acetate (25), were identified as novel natural products via a Jurkat cell antiproliferation screening study (Figure 9) [20]. Using LCMSguided screening of Streptomyces sp.…”