Characterization of anti-BCG benz[α]anthraquinones and new siderophores from a Xinjiang desert–isolated rare actinomycete Nocardia sp. XJ31

Abstract

The current global demand for novel anti-TB drugs has drawn urgent attention on the discovery of natural product compounds with anti-TB activity. Lots of efforts have emphasized on environmental samples from unexplored or underexplored natural habits and identified numerous rare actinomycete taxa producing structurally diverse bioactive natural products. Herein, we report a survey of the rare actinobacteria diversity in Xinjiang region together with the discovery of anti-TB active natural products from these strains. We have collected 17 soil samples at different sites with different environmental conditions, from which 39 rare actinobacteria were identified by using a selective isolation strategy with 5 media variations. Among those isolated strains, XJ31 was identified as a new Nocardia sp. based on 16S rRNA gene analysis. Through one strain-many compounds (OSMAC) strategy combined with anti-Bacillus Calmette-Guérin bioassay-guided isolation, two groups of compounds were identified. They were twelve siderophores (nocardimicins, 1-12) and two anthraquinones (brasiliquinones, 13 and 14) and ten of them were identified as new compounds. The structures of the purified compounds were elucidated using HR-ESI-MS, 1D NMR, and 2D NMR techniques. The anti-TB bioassays revealed that the two benz[α]anthraquinones have potent activity against BCG (MICs = 25 μM), which can be used as a promising start point for further anti-TB drug development. Key points • Ten new natural products were identified from Nocardia sp. XJ31. • Brasiliquinones 13 and 14 showed moderate anti-BCG activity.

Diversity and adaptation properties of actinobacteria associated with Tunisian stone ruins

“…Many studies have emphasized environmental samples from unexplored or underexplored natural habitats (Zhang et al, 2020). Among these habitats, stones are complex environments composed of several micro-niches that permit the proliferation of several microorganisms despite the harsh conditions resulting from low water and nutrient availability (Cockell et al, 2002;10.3389/fmicb.2022.997832 Frontiers in Microbiology 13 frontiersin.org TABLE 3 Biocontrol potential of bacterial isolates against pathogenic (A) bacteria and (B) fungi.…”

Two novel aliphatic unsaturated alcohols isolated from a pathogenic fungus Fusarium proliferatum

“…Recently, poorly tapped biological resources, including rare actinobacteria, endophytic fungi, and even phytopathogenic fungi, have been explored as innovative resources for discovering novel natural products with promising bioactivity [ [24] , [25] , [26] ]. Among them, phytopathogenic fungi play an important, but yet rarely explored role.…”

Actinobacteria From Desert: Diversity and Biotechnological Applications

“…One new anthraquinone, brasiliquinone E produced by Nocardia sp. XJ31 from the Xinjiang Desert, demonstrated modest anti- Bacillus Calmette-Guérin (BCG) activity in an antituberculosis (anti-TB) assay ( Zhang et al, 2020 ). The anti-TB activity indicated that brasiliquinone E can be used as a potential treatment for MDR TB.…”

“…Nocardia sp. XJ31, isolated from the Xinjiang Desert, generated nine new siderophores (nocardimicins J–R), which were found to inhibit viral infection by binding affinities with the four 3′′-RNA pockets of viral polymerases (>90%) ( Zhang et al, 2020 ).…”