Antibacterial Activity of Endophytic Actinomycetes Isolated from the Medicinal Plant Vochysia divergens (Pantanal, Brazil)

Abstract

Endophytic actinomycetes from medicinal plants produce a wide diversity of secondary metabolites (SM). However, to date, the knowledge about endophytes from Brazil remains scarce. Thus, we analyzed the antimicrobial potential of 10 actinomycetes isolated from the medicinal plant Vochysia divergens located in the Pantanal sul-mato-grossense, an unexplored wetland in Brazil. Strains were classified as belonging to the Aeromicrobium, Actinomadura, Microbacterium, Microbispora, Micrococcus, Sphaerisporangium, Streptomyces, and Williamsia genera, through morphological and 16S rRNA phylogenetic analyzes. A susceptibility analysis demonstrated that the strains were largely resistant to the antibiotics oxacillin and nalidixic acid. Additionally, different culture media (SG and R5A), and temperatures (28 and 36°C) were evaluated to select the best culture conditions to produce the active SM. All conditions were analyzed for active metabolites, and the best antibacterial activity was observed from metabolites produced with SG medium at 36°C. The LGMB491 (close related to Aeromicrobium ponti) extract showed the highest activity against methicillin-resistant Staphylococcus aureus (MRSA), with a MIC of 0.04 mg/mL, and it was selected for SM identification. Strain LGMB491 produced 1-acetyl-β-carboline (1), indole-3-carbaldehyde (2), 3-(hydroxyacetyl)-indole (4), brevianamide F (5), and cyclo-(L-Pro-L-Phe) (6) as major compounds with antibacterial activity. In this study, we add to the knowledge about the endophytic community from the medicinal plant V. divergens and report the isolation of rare actinomycetes that produce highly active metabolites.

Screening of metabolites from endophytic fungi of some Nigerian medicinal plants for antimicrobial activities

“…Indole-3-carbaldehyde (indole-3-carboxaldehyde), an indole alkaloid, had been isolated from an endophytic Lasiodiplodia sp. associated with Viscum coloratum (96), from endophytic actinomycetes (85,97), from Pseudomonas sp. (98), and from a Red Sea sponge Hyrtios erectus (86).…”

“…(98), and from a Red Sea sponge Hyrtios erectus (86). Indole-3-carbaldehyde showed moderate cytotoxic (86) and antibacterial activities (85). In plants, indole-3-carbaldehyde is associated with the innate immunity to microbial pathogen infections (84,85).…”

Anti-MRSA Activity of Actinomycin X2 and Collismycin A Produced by Streptomyces globisporus WA5-2-37 From the Intestinal Tract of American Cockroach (Periplaneta americana)

“…Therefore, there is an emerging demand for discovery of novel, safe and potent bioactive compounds with anti-MRSA activity (Uchida et al, 2014). Therefore, more and more research efforts have focused on the exploration of microorganism to discover bioactive secondary metabolites (Gos et al, 2017;Sadaf et al, 2018;Lee et al, 2018). But with decreased of the identification of natural products from traditional sources, scientists have turned their eyes to the microorganism from new sources such as insects (Beemelmanns et al, 2017;Ma et al, 2017).…”

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“…Endophytes have great importance in the production of compounds with a unique structure, which may result from several biological interactions [47], however, the challenge for drug discovery is how to access this chemical potential. Most of the studies on endophytic biodiversity published in Brazil (2012-2017) present some bioprospecting studies, such as evaluation of antibiotic, antioxidant, antiparasitic, or cytotoxicity activities, or the use of endophytes to promote plant growth or reactive dye discoloration [40,[48][49][50][51][52][53][54] (▶ Table 3). As a result of the success obtained in terms of discovering active metabolite-producing endophytes, a large number of compounds [2,[55][56][57] or known compounds with unreported biological properties [33,36,[58][59][60] have been reported.…”