Diketopiperazines from the Endophytic Streptomyces triticiradicis TTCF1 (Tinospora cordifolia): Isolation and Evaluation of Antibacterial and Anticancer Properties

Pak J Biol Sci. 2025 Dec;28(12):735-748. doi: 10.3923/pjbs.2025.735.748.

ABSTRACT

&lt;b&gt;Background and Objective:&lt;/b&gt; Endophytic actinomycetes associated with medicinal plants constitute a valuable yet underinvestigated source of bioactive secondary metabolites. &lt;i&gt;Tinospora cordifolia&lt;/i&gt;, a widely respected ethnomedicinal plant, harbors diverse microbial endophytes with strong therapeutic potential. This study aimed to isolate and characterize endophytic actinomycetes from &lt;i&gt;T. cordifolia&lt;/i&gt;, identify their major metabolites and evaluate the antibacterial, anticancer and molecular inhibitory properties of the purified compounds. &lt;b&gt;Materials and Methods:&lt;/b&gt; Actinomycetes were isolated from surface-sterilized root, stem and leaf tissues using selective media. The most potent isolate, TTCF1, was identified through morphological characteristics, chemotaxonomic profiling and 16S rRNA gene sequencing. Bioactive metabolites were extracted and purified via column chromatography, followed by structural characterization using advanced spectroscopic techniques. Antibacterial activity was assessed by determining MIC and MBC values against human pathogens, including MRSA. Cytotoxicity was evaluated using the MTT assay on HeLa, HepG2 and MDA-MB-231 cancer cell lines, along with Vero cells as the non-cancerous control. Molecular docking was performed against EGFR, accompanied by ADMET property prediction. Statistical significance was determined using one-way ANOVA with Tukey’s &lt;i&gt;post hoc&lt;/i&gt; test (p<0.05). &lt;b&gt;Results:&lt;/b&gt; Ten actinomycete isolates were obtained, all exclusively from root tissues. The strongest producer, TTCF1, showed 99.54% 16S rRNA similarity to &lt;i&gt;Streptomyces triticiradicis&lt;/i&gt;. Chemical analysis yielded two diketopiperazines: Cyclo-(D-Pro-L-Tyr) and Cyclo-(D-Pro-L-Leu). Both compounds demonstrated potent antibacterial activity against Gram-positive pathogens (MIC 32-64 μg/mL) and cytotoxicity toward cancer cell lines (IC&lt;sub&gt;50&lt;/sub&gt; 58.16-362.71 μg/mL). Compound 1 showed selective toxicity toward HepG2 cells and exhibited stronger predicted EGFR binding affinity (-7.188 kcal/mol) than the reference inhibitor AQ4 (-6.703 kcal/mol). The ADMET profiles indicated good oral absorption. &lt;b&gt;Conclusion:&lt;/b&gt; &lt;i&gt;Streptomyces triticiradicis&lt;/i&gt; TTCF1 is a promising source of pharmacologically relevant diketopiperazines. Cyclo-(D-Pro-L-Tyr) emerges as a potential lead molecule with notable antimicrobial and selective anticancer activity, supported by strong EGFR-binding predictions.

PMID:41618675 | DOI:10.3923/pjbs.2025.735.748