Anthraquinones from the Endophytic Streptomyces griseoincarnatus SB03 (Ocimum basilicum): Isolation and Evaluation of Antibacterial and Cytotoxic Activities

<b>Background and Objective:</b> The rising global challenge of drug resistance and cancer demands the discovery of novel therapeutic agents. Endophytic microorganisms, particularly those from medicinal plants like <i>Ocimum basilicum</i>, represent a promising, yet underexplored, source of natural products. This study aimed to isolate and screen bioactive endophytic actinomycetes from <i>O. basilicum</i> roots. The research focused on characterizing the most active isolate, purifying its secondary metabolites and evaluating their antibacterial and anticancer properties. <b>Materials and Methods:</b> The potent strain SB03 was isolated from basil roots and identified as <i>Streptomyces griseoincarnatus</i> using 16S rDNA sequencing. Two compounds were purified from its crude extract and structurally characterized by spectroscopy. Their bioactivities were assessed by determining MIC/MBC against pathogenic bacteria (including MRSA) and IC<sub>50</sub> against human cancer cells (HeLa, HepG2 and MDA-MB-231). Molecular docking investigated their interaction with topoisomerase II, complemented by <i>in silico</i> ADMET analysis. <b>Results:</b> A potent actinomycete strain, <i>S. griseoincarnatus</i> SB03, was successfully isolated from sweet basil roots. Two known anthraquinone compounds, 2-butyryl-1,8-dihydroxy-3-methyl-anthraquinone (Compound <b>1</b>) and 2-butyryl-1,4,8-trihydroxy-3-methyl-anthraquinone (Compound <b>2</b>), were isolated from the culture extract. Both exhibited strong antibacterial activity (MIC 64-128 μg/mL against Gram-positive strains) and significant cytotoxicity (IC<sub>50</sub> 35.01-97.68 μg/mL) against all tested cancer lines. Importantly, they showed a higher selectivity index against the HepG2 line than the control, doxorubicin. Docking studies indicated favorable binding to topoisomerase II. <b>Conclusion:</b> <i>Streptomyces griseoincarnatus</i> SB03 from sweet basil is a promising source of therapeutic agents. Its anthraquinone metabolites possess valuable dual antibacterial and selective anticancer properties. These compounds are excellent lead candidates for future drug development against infectious diseases and hepatocellular carcinoma.