Isolation, purification and chemical characterization of a new angucyclinone compound produced by a new halotolerant Nocardiopsis sp. HR-4 strain

Abstract

A halotolerant Actinobacteria strain HR-4 was isolated from a salt lake soil sample in Algerian Sahara. Analysis of 16S rDNA gene sequence showed that strain HR-4 belonged to the genus Nocardiopsis. The similarity level ranges between 97.45 and 99.20% with Nocardiopsis species and Nocardiopsis rosea being the most closely related one. Morphological, physiological and phylogenetic characteristics comparisons showed significant differences with the nearest species. These data strongly suggest that strain HR-4 represents novel species. The antimicrobial activity of strain HR-4 showed an antibacterial activity against Gram-positive bacteria as well as an antifungal one. Two major natural products including a new one were isolated from the culture broth using various separation and purification procedures. The chemical structure established on the basis of spectroscopic studies NMR and by comparing with spectroscopic data from the literature of the two compounds affirm that they are classified in the group of Angucyclinones. This is the first report of a production of this type of molecules by the genus Nocardiopsis. The new natural compound was established as (-)-7-deoxy-8-O-methyltetrangomycin with a new configuration.

Actinobacteria Derived from Algerian Ecosystems as a Prominent Source of Antimicrobial Molecules

“…and reported without the stereochemical assignment at this centre [102]. These metabolites exhibited good antibacterial activities only against Gram-positive bacteria [103].…”

Concepts and Methods to Access Novel Antibiotics from Actinomycetes

“…Other recent examples for the empiric progress in isolation of actinomycetes is the halotolerant Nocardiopsis sp. HR-4 strain producing (-)-7-deoxy-8- O -methyltetrangomycin [ 28 ] and the non-extremophilic Streptomyces spp. ERI-26 producing 6,6 1 -bis(1,5,7-trihydroxy-3-hydroxylmethylanthraquinone) [ 29 , 30 ].…”

“…Similar antibiotic bioactivity profile was exhibited by the halotolerant Nocardiopsis sp. HR-4 recently isolated from salt lake soil sample in Algerian Sahara [ 28 ], however the activities were not connected to known or novel natural products. One of the more promising compounds is actinomadurol, also isolated from a rare actinomycete Actinomadura strain KC 191 as it exhibits potent activity against S. aureus , K. rhizophila , and P. hauseri (MIC = 0.39–0.78 μg/mL) [ 70 ].…”

“…ERI-26 [ 29 , 30 ] and (-)-7-deoxy-8- O -methyltetrangomycin from Nocardiopsis sp. HR-4 [ 28 ] are examples for novel metabolites found using this conventional method. ( B ) Soil sample or marine sample is co-cultivated with other microorganisms to promote culturable isolates or to stimulate the secondary metabolism.…”

Natural Product Potential of the Genus Nocardiopsis

“…Bioactivity tests with extracts of strain HR-4 showed an antibacterial activity against namely S. aureus , E. faecalis , and M. luteus , as well as antifungal properties against S. cerevisiae and C. albicans . Chemical investigations led to the isolation and identification of two major angucyclinones, namely, 8- O -methyltetrangomycin ( 38 ) and (−)-7-deoxy-8- O -methyltetrangomycin ( 39 ) [ 40 ]. Structures are shown in Figure 5 .…”