Chemical investigations of the termite-associated Streptomyces tanashiensis BYF-112 resulted in the discovery of four novel alkaloid derivatives: vegfrecines A and B (1 1 and 2 ), exfoliazone A (3), 3 ), and venezueline H (7), 7 ), in addition to nine known metabolites (4-6, 4 - 6 , 8 - 13 ). The structures of these compounds were elucidated through comprehensive spectroscopic analysis and comparison with existing literature data. Antibacterial assays revealed that viridomycin A (11) 11 ) exhibited potent antibacterial activity against Staphylococcus aureus, , with a zone of inhibition (ZOI) of 12.67 mm, in comparison to a ZOI of 17.67 mm for the positive control gentamicin sulfate. Viridomycin A (11) 11 ) showed moderate activity against Micrococcus tetragenus and Pseudomonas syringae pv. actinidae, , with ZOI values of 15.50 and 14.33 mm, respectively, which were inferior to those of gentamicin sulfate (34.67 and 24.00 mm). Viridomycin F (12) 12 ) also exhibited moderate antibacterial effects against S. aureus, , M. tetragenus, , and P. syringae pv. actinidae, , with ZOI values of 8.33, 16.50, and 10.83 mm, respectively. Cytotoxicity assays demonstrated that viridobruunine A (5), 5 ), exfoliazone (6), 6 ), viridomycin A (11), 11 ), and X-14881E (13) 13 ) exhibited significant cytotoxicity against human malignant melanoma (A375), ovarian cancer (SKOV-3), and gastric cancer (MGC-803) cell lines, with IC50 50 values ranging from 4.61 to 19.28 mu molL-1. -1 . Furthermore, bioinformatic analysis of the complete genome of S. tanashiensis suggested a putative biosynthetic gene cluster (BGC) responsible for the production of compounds 1-12. . These findings indicate that the secondary metabolites of insect-associated S. tanashiensis BYF-112 hold promise as potential sources of novel antibacterial and anticancer agents.