Solphenazines A–F, Glycosylated Phenazines from Streptomyces sp. Strain DL-93

Abstract

During a survey of actinobacteria known to suppress the growth of Streptomyces scabies (the causative agent of potato scab disease) in vivo, six new rhamnosylated alkaloids, the solphenazines A-F (1-6), were isolated from a biological control strain of Streptomyces (DL-93). The known rhamnosyl analogue of paraben (9) was also isolated along with a new rhamnosylated derivative of N-methyl-p-aminobenzoic acid (10). None of the compounds exhibited any antibacterial or antifungal activity against a standard panel of microorganisms, but compounds 1, 2, and 6 displayed some cytotoxicity against HCT-116 cancer cells. Additional in vitro testing provided data suggesting that the cytotoxic activity is not due to DNA intercalation or topoisomerase inhibition.

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“…The aglycone was also confirmed by comparison of the spectral data with the literature. [29][30][31] Analysis of the COSY spectrum revealed one contiguous spin system formed by correlations of five oxygen-bearing methines and one doublet methyl signal at δ H 1.39, confirming the deoxyhexapyranose. The connectivity of the 6-deoxysugar to the aglycone was confirmed from the HMBC long-range coupling of H-8 (δ H 7.97) and H-1′ (δ H 6.03) to the C-6 (δ C 152.8) of the phenazine nucleus.…”

“…As mentioned above, few glycosylated phenazines have so far been found in nature, most of which are rhamnosides with significant bioactivity. 30,31 Endophenasides A (1) and C (3) are the first example for 2′-O-methylation of the rhamnose moiety in the phenazine glycosides.…”

“…27,[30][31][32][33] Indeed, the prenyl-and the carboxyl group on the phenazine core of compounds 1-4, could be either 1,6-or 1,9-disubstituted. However, the presence of a 1,9-disubstituted pattern is deduced from previous analysis of the aglycone moiety 27 that is also present in compounds 2-4.…”

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“…These fractions were subsequently purified using Sephadex LH‐20 size exclusion media, flash chromatography using an ISCOcombiflash instrument, and semipreparative reversed phase C‐18 high performance liquid chromatography separations (Agilent 1260). Pure compounds were identified and characterized using nuclear magnetic resonance spectroscopy, mass spectrometry, optical rotation measurements, circular dichroism spectroscopy and semi‐synthesis 35,77,78 …”

“…Pure compounds were identified and characterized using nuclear magnetic resonance spectroscopy, mass spectrometry, optical rotation measurements, circular dichroism spectroscopy and semi-synthesis. 35,77,78 The mycelia and supernatants from liquid cultures were separated by filtration and separately extracted three times using methanol and ethyl acetate, respectively. Supernatants were also subsequently extracted with n-butanol.…”