Elsevier

Tetrahedron Letters

Volume 59, Issue 51, 19 December 2018, Pages 4496-4499
Tetrahedron Letters

Symbiodinolactone A, a new 12-membered macrolide from symbiotic marine dinoflagellate Symbiodinium sp.

https://doi.org/10.1016/j.tetlet.2018.11.018Get rights and content

Highlights

Abstract

A new 12-membered macrolide, symbiodinolactone A, was isolated from the culture broth of symbiotic marine dinoflagellate Symbiodinium sp. The gross structure of symbiodinolactone A was elucidated by spectroscopic analyses, and the relative configuration was elucidated by the J-based configuration analysis and density-functional theory calculations. Symbiodinolactone A is the new 12-membered macrolide possessing an E double bond between C-4 and C-5, a branched methyl group at C-7, and a 1,2,3-trihydroxybutyl group at C-11. Symbiodinolactone A is the first usual size macrolide and the first non-nitrogen-containing macrolide from dinoflagellate Symbiodinium sp. Symbiodinolactone A might be generated by the unexplained dinoflagellate polyketide biosynthetic machinery.

Introduction

The marine dinoflagellate has been recognized as the producer of novel natural products with intriguing structures and significant bioactivities [1]. Especially, the carbon skeletons of dinoflagellate polyketides, that might be synthesized by unexplained dinoflagellate polyketide biosynthetic machinery, are unique and unavailable from other organisms [2]. In our continuing search for bioactive natural products from marine dinoflagellates, we have isolated a series of macrolides, amphidinolides, and long chain polyketides from the cells of cultured dinoflagellates Amphidinium spp. [3]. In 2012, we collected a marine acoelomorpha Amphiscolops sp. at Okinawa, which was harboring dinoflagellates Amphidinium sp. (2012-7-4A strain) and Symbiodinium sp. (2012-7-4S strain). We have isolated two known macrolides, amphidinolides P [4] and Q [5], a known linear polyketide, amphidinin A [6], and five new linear polyketides, amphidinins C-G [7], [8], from the culture medium of dinoflagellates Amphidinium sp. (2012-7-4A strain). Recently, we investigated the culture medium of dinoflagellates Symbiodinium sp. (2012-7-4S strain) and resulted in isolation of a new 12-membered macrolide, symbiodinolactone A (1) (Fig. 1). Here, we describe the isolation and structure elucidation of 1.

Section snippets

Results and discussion

The dinoflagellates Symbiodinium sp. (2012-7-4S strain) were isolated from inside of a marine acoelomorpha Amphiscolops sp. collected at Ishigaki Island, Okinawa, Japan. The dinoflagellates were cultured at 25 °C for 3 weeks under 16 h light/8h dark schedule in seawater medium and the supernatant was subjected to a porous polymer gel column. The column was washed with H2O and the adsorbed material was eluted with MeOH, which was concentrated in vacuo and partitioned between organic solvents (n

Conclusion

Symbiodinolactone A (1) is the new 12-membered macrolide possessing an E double bond between C-4 and C-5, a branched methyl group at C-7, and a 1,2,3-trihydroxybutyl group at C-11. Though the 62-membered or more large giant macrolides possessing a nitrogen-containing long side chain, such as zooxanthellatoxins A and B [12], zooxanthellamides Cs [13], and symbiodinolide [14], have been isolated from dinoflagellates Symbiodinium sp., 1 is the first usual size macrolide and the first

Acknowledgments

We thank Mr. K. Chiba, The Instrument Analysis Equipment Research Center, Showa Pharmaceutical University, for measurements of MS. This work was partly supported by the Naito Foundation, the Shorai Foundation for Science and Technology, a Grant-in-Aid for Young Scientists of Showa Pharmaceutical University, MEXT-Supported Program for the Strategic Research Foundation at Private Universities (2013–2017), and JSPS KAKENHI Grant Number JP17K08345.

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