<b>Background and Objective:</b> The AL22 strain was isolated from the rhizosphere soil of <i>Alpinia galanga</i> (L.) Willd (Zingiberaceae) and identified as <i>Microbispora</i> sp., by analysing its morphology, chemotaxonomy and 16S rDNA sequence. Previous studies demonstrated the bactericidal effects of its crude extract against <i>Bacillus cereus</i>, <i>Bacillus subtilis</i>, <i>Staphylococcus aureus</i> and methicillin-resistant <i>Staphylococcus aureus</i>. The present study aimed to isolate the major compounds and evaluate their biological properties. <b>Materials and Methods:</b> Silica gel column chromatography and thin-layer chromatography were used for the purification and identification of 3,4-dihydro-lactucin (compound <b>1</b>) and umbelliferone (compound <b>2</b>) by NMR and mass spectrometry, respectively. Antibacterial and anticancer activities were carried out. <b>Results:</b> The bioassay studies illustrated that compound <b>1</b> had antibacterial activity against gram-positive bacteria, with its minimum inhibitory concentration and minimum bactericidal concentration of 16-32 and 64-128 μg mL<sup></sup><sup>1</sup>, respectively. The crude extract and purified compounds showed weak cytotoxic activity on the L929 and Vero cells with IC<sub>50</sub> values >512.00 μg mL<sup></sup><sup>1</sup>. The cytotoxicity of compound <b>1</b> was observed in the MDA-MB-231 and HeLa cells with IC<sub>50</sub> values of 37.62 and 75.34 μg mL<sup></sup><sup>1</sup>, respectively, while its IC<sub>50</sub> value against the HepG2 cells was 456.67 μg mL<sup></sup><sup>1</sup>. <b>Conclusion:</b> These findings showed that compound <b>1</b> of <i>Microbispora</i> sp., AL22 exhibited antibacterial and anticancer activities. Extensive studies on 3,4-dihydro-lactucin could lead to the development of beneficial approaches for managing bacterial infections and cancer.
Keywords: 3; 4-dihydro-lactucin; AL22; Alpinia galanga; Microbispora sp.; antibacterial activity; anticancer activity; bioactive compounds; endophytic actinomycetes.