Antibacterial and Anticancer Properties of Anthraquinones from Streptomyces galbus AVL08, An Endophyte in Aloe vera Linn.

Abstract

<b>Background and Objective:</b> Endophytic actinomycetes represent a promising source of novel bioactive compounds. This study aimed to isolate and characterize endophytic actinomycetes from <i>Aloe vera</i> leaves, identify their bioactive metabolites and assess their antimicrobial and anticancer properties. <b>Materials and Methods:</b> Endophytic actinomycetes were isolated from <i>Aloe vera</i> leaf sections and screened for antimicrobial activity. Isolate AVL08, exhibiting potent activity against <i>Staphylococcus aureus</i>, was identified using 16S rRNA gene sequencing and morphological characterization. Bioactive compounds were extracted, purified and identified using spectroscopic methods. Antimicrobial activity was evaluated using microbroth dilution assays and cytotoxicity was assessed against Vero, HeLa, HepG2 and MDA-MB-231 cell lines. Molecular docking studies were performed to investigate interactions with human DNA topoisomerase II. <i>In silico</i>, ADMET predictions were conducted using SwissADME, PreADMET and pkCSM. Statistical analysis was performed using SPSS (version 11.01) with One-way ANOVA and Tukey's <i>post hoc</i> test, considering differences significant at p<0.05. <b>Results:</b> Isolate AVL08 was identified as <i>Streptomyces galbus</i> and produced two anthraquinone compounds, 1,4,6-trihydroxy-8-(2'-oxopentyl)-9,10-anthraquinone (<b>1</b>) and 1,4,6-trihydroxy-8-pentacarboxyl-9,10-anthraquinone (<b>2</b>). These compounds exhibited selective antibacterial activity against Gram-positive bacteria and significant cytotoxicity against MDA-MB-231 and HeLa cancer cell lines, with IC₅₀ values ranging from 94.00 to 154.52 μg/mL. Compound <b>2</b> demonstrated enhanced potency and selectivity against HepG2 cells. Molecular docking revealed favorable interactions of the anthraquinones with topoisomerase II. The ADMET predictions indicated favorable pharmacokinetic profiles but highlighted potential hERG channel inhibition and mutagenicity in specific bacterial strains. <b>Conclusion:</b> <i>Streptomyces galbus</i> AVL08 is a promising source of bioactive anthraquinones with potent antimicrobial and anticancer properties. The identified compounds, particularly Compound <b>2</b>, warrant further investigation for therapeutic applications. This study highlights the potential of endophytic actinomycetes from <i>Aloe vera</i> as a valuable resource for drug discovery.