# Biochemical characterization of actinomycete from Namibia rocky crest mountainous soil and analyzing their bioactive metabolites for antagonistic effect against human respiratory pathogens

## TL;DR

This study explores actinomycete bacteria from Namibian soil for their potential to produce bioactive compounds that fight respiratory pathogens and show antioxidant properties.

## Contribution

The study identifies new actinomycete isolates with strong antimicrobial and antioxidant properties from an unexplored region.

## Key findings

- Three actinomycete isolates showed strong inhibition of Streptococcus pneumonia with growth inhibition zones up to 27 mm.
- All isolates exhibited potent activity against Stachybotrys chartarum with inhibition zones up to 48 mm.
- Chloroform extracts demonstrated high antioxidant activity with up to 73% DPPH scavenging.

## Abstract

the present study aimed at isolating and characterizing actinomycete from unexplored Windhoek rocky crest mountainous soil and extracting bioactive metabolites as possible therapeutics against common life-threatening Streptococcus pneumonia (S. pneumonia) and Stachybotrys chartarum (S. chartarum).

chemotaxonomy and biochemical methods were used to identify the isolates. The solvent extraction method was used to extract bioactive compounds. Agar overlay and disc diffusion methods were used to determine the antimicrobial activity of isolates and extracted bioactive metabolites against S. pneumonia and S. chartarum. The antioxidant activity of the extracted bioactive metabolites was determined using 2.2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method with ascorbic acid as a positive control. Comparison between groups was done using a Two-way ANOVA, followed by Bonferroni post-test.

three distinct isolates from 3 soil samples were identified on starch casein agar and distinguished using biochemical tests. All three isolates showed strong inhibitory activity against S. pneumonia with average growth inhibition zones between 18.0±1.00 and 27±0.00 mm p< 0.005. All isolates showed potent inhibitory activity against S. chartarum with the average inhibition zones ranging between 42.0±1.00 and 48±0.00 mm, p< 0.005. The chloroform extracts showed potent DPPH activity of up to 73± 1.41%.

growth conditions and extraction solvents can influence the antimicrobial and antioxidant properties of bioactive metabolites.