Antibacterial and Anticancer Properties of Microbispora sp., AL22: An Endophyte of Alpinia galanga (L.) Willd

Thongchai Taechowisan, Thanaporn Chuen-Im and Waya Phutdhawong

Background and Objective: The AL22 strain was isolated from the rhizosphere soil of Alpinia galanga (L.) Willd (Zingiberaceae) and identified as Microbispora sp., by analysing its morphology, chemotaxonomy and 16S rDNA sequence. Previous studies demonstrated the bactericidal effects of its crude extract against Bacillus cereus, Bacillus subtilis, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. The present study aimed to isolate the major compounds and evaluate their biological properties. Materials and Methods: Silica gel column chromatography and thin-layer chromatography were used for the purification and identification of 3,4-dihydro-lactucin (compound 1) and umbelliferone (compound 2) by NMR and mass spectrometry, respectively. Antibacterial and anticancer activities were carried out. Results: The bioassay studies illustrated that compound 1 had antibacterial activity against gram-positive bacteria, with its minimum inhibitory concentration and minimum bactericidal concentration of 16-32 and 64-128 μg mL^–1, respectively. The crude extract and purified compounds showed weak cytotoxic activity on the L929 and Vero cells with IC₅₀ values >512.00 μg mL^–1. The cytotoxicity of compound 1 was observed in the MDA-MB-231 and HeLa cells with IC₅₀ values of 37.62 and 75.34 μg mL^–1, respectively, while its IC₅₀ value against the HepG2 cells was 456.67 μg mL^–1. Conclusion: These findings showed that compound 1 of Microbispora 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.

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