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Open AccessCommunication

Hybrid Polyketides from a Hydractinia-Associated Cladosporium sphaerospermum SW67 and Their Putative Biosynthetic Origin

1
School of Pharmacy, Sungkyunkwan University, Suwon 16419, Korea
2
Leibniz Institute for Natural Product Research and Infection Biology e.V., Hans-Knöll-Institute (HKI), 07745 Jena, Germany
3
Laboratory of Nuclear Magnetic Resonance, National Center for Inter-University Research Facilities (NCIRF), Seoul National University, Gwanak-gu, Seoul 08826, Korea
4
College of Korean Medicine, Gachon University, Seongnam 13120, Korea
5
Department of Chemistry, Yale University, New Haven, CT 06520, USA
6
Chemical Biology Institute, Yale University, West Haven, CT 06516, USA
*
Authors to whom correspondence should be addressed.
Mar. Drugs 2019, 17(11), 606; https://doi.org/10.3390/md17110606
Received: 22 August 2019 / Revised: 16 October 2019 / Accepted: 20 October 2019 / Published: 24 October 2019
(This article belongs to the Special Issue Synthetic and Biosynthetic Approaches to Marine Natural Products)
Five hybrid polyketides (1a, 1b, and 24) containing tetramic acid core including a new hybrid polyketide, cladosin L (1), were isolated from the marine fungus Cladosporium sphaerospermum SW67, which was isolated from the marine hydroid polyp of Hydractinia echinata. The hybrid polyketides were isolated as a pair of interconverting geometric isomers. The structure of 1 was determined based on 1D and 2D NMR spectroscopic and HR-ESIMS analyses. Its absolute configuration was established by quantum chemical electronic circular dichroism (ECD) calculations and modified Mosher’s method. Tetramic acid-containing compounds are reported to be derived from a hybrid PKS-NRPS, which was also proved by analyzing our 13C-labeling data. We investigated whether compounds 14 could prevent cell damage induced by cisplatin, a platinum-based anticancer drug, in LLC-PK1 cells. Co-treatment with 2 and 3 ameliorated the damage of LLC-PK1 cells induced by 25 μM of cisplatin. In particular, the effect of compound 2 at 100 μM (cell viability, 90.68 ± 0.81%) was similar to the recovered cell viability of 88.23 ± 0.25% with 500 μM N-acetylcysteine (NAC), a positive control. View Full-Text
Keywords: hybrid polyketides; tetramic acid; Cladosporium sphaerospermum; hybrid PKS-NRPS; LLC-PK1 cells hybrid polyketides; tetramic acid; Cladosporium sphaerospermum; hybrid PKS-NRPS; LLC-PK1 cells
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MDPI and ACS Style

Lee, S.R.; Lee, D.; Eom, H.J.; Rischer, M.; Ko, Y.-J.; Kang, K.S.; Kim, C.S.; Beemelmanns, C.; Kim, K.H. Hybrid Polyketides from a Hydractinia-Associated Cladosporium sphaerospermum SW67 and Their Putative Biosynthetic Origin. Mar. Drugs 2019, 17, 606.

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