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Molecules 2016, 21(9), 1116; doi:10.3390/molecules21091116

Bioactive 2(1H)-Pyrazinones and Diketopiperazine Alkaloids from a Tunicate-Derived Actinomycete Streptomyces sp.

1
Natural Products Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah 21589, Saudi Arabia
2
Suez Canal University Hospital, Suez Canal University, Ismailia 41522, Egypt
3
Department of Natural Products, Faculty of Pharmacy, King Abdulaziz University, Jeddah 21589, Saudi Arabia
4
Department of Pharmacognosy, Faculty of Pharmacy, Suez Canal University, Ismailia 41522, Egypt
5
Special Infectious Agents Unit, Fahd Medical Research Center, King Abdulaziz University, Jeddah 21589, Saudi Arabia
*
Author to whom correspondence should be addressed.
Academic Editor: Isabel C. F. R. Ferreira
Received: 8 May 2016 / Revised: 11 August 2016 / Accepted: 16 August 2016 / Published: 24 August 2016
(This article belongs to the Collection Bioactive Compounds)
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Abstract

As a part of our ongoing effort to allocate marine microbial bioactive leads, a tunicate-derived actinomycete, Streptomyces sp. Did-27, was investigated. Three new 2(1H)-pyrazinones derivatives, (S)-6-(sec-butyl)-3-isopropylpyrazin-2(1H)-one (1), (S)-3-(sec-butyl)-6-isopropylpyrazin-2(1H)-one (2) and (S)-6-(sec-butyl)-3-isobutylpyrazin-2(1H)-one (3), together with the known (1H)-pyrazinones analogues deoxymutaaspergillic acid (4), 3,6-diisobutyl-2(1H)-pyrazinone (5) and 3,6-di-sec-butyl-2(1H)-pyrazinone (6), and the diketopiperazine alkaloids cyclo(6-OH-d-Pro-l-Phe) (7), bacillusamide B (8), cyclo(l-Pro-l-Leu) and cyclo(l-Pro-l-Ile) (10) were isolated from this strain. The structures of the compounds were determined by study of their one- and two-dimensional NMR spectra as well as high-resolution mass spectral determinations. Compound 4 was reported previously as a synthetic product, while compound 6 was reported as 2-hydroxy-3,6-di-sec-butylpyrazine. Herein, we report the complete NMR data for compounds 4 and 6. The compounds were evaluated for their cytotoxic activities against three cell lines. Compound 5 showed potent and selective activity against HCT-116 cell line with IC50 of 1.5 μg/mL, while 110 showed variable cytotoxic activities against these cancer cell lines. These results provide further understanding about the chemistry and bioactivities of the alkylated 2(1H)-pyrazinone derivatives. View Full-Text
Keywords: Red Sea Didemnum sp.; Streptomyces sp. Did-27; alkylated 2(1H)-pyrazinone derivatives; diketopiperazine alkaloids; cancer cell lines; antiproliferative and cytotoxic activities Red Sea Didemnum sp.; Streptomyces sp. Did-27; alkylated 2(1H)-pyrazinone derivatives; diketopiperazine alkaloids; cancer cell lines; antiproliferative and cytotoxic activities
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Shaala, L.A.; Youssef, D.T.A.; Badr, J.M.; Harakeh, S.M. Bioactive 2(1H)-Pyrazinones and Diketopiperazine Alkaloids from a Tunicate-Derived Actinomycete Streptomyces sp.. Molecules 2016, 21, 1116.

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