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 1–10 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.
Highlights
The genus Streptomyces was first described by Waksman and Henrici [1] and is considered as a promising resource for bioactive natural products and drug discovery [2,3]
Compound 5 showed potent and selective activity against HCT-116 cell line with IC50 of 1.5 μg/mL, while 1–10 showed variable cytotoxic activities against these cancer cell lines. These results provide further and deeper insight into the chemical diversity and biological activities the alkylated 2(1H)-pyrazinone derivatives
All other compounds were moderatly active against MCF-7 and weakly active against HepG2 cell line
Summary
The genus Streptomyces was first described by Waksman and Henrici [1] and is considered as a promising resource for bioactive natural products and drug discovery [2,3]. As a part of our ongoing effort to allocate bioactive leads from marine microbes [7,8,9], we have investigated a tunicate-derived actinomycete, Streptomyces sp. Bioassay-guided fractionation of the active fractions of an organic extract of this strain resulted in the isolation and identification of three new alkylated 2(1H)-pyrazinone derivatives including (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 deoxymutaaspergillic acid. Four diketopiperazine alkaloids including cyclo(6-OH-D-Pro-L-Phe) (7) [27], bacillusamide B (8) [28], cyclo(L-Pro-L-Leu) (9) [29] and cyclo(L-Pro-L-Ile) (10) [30] were isolated from the extract of the marine
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