Synthesis and biological evaluation of marine alkaloid-oriented β-carboline analogues

Pityriacitrin is a marine alkaloid with typical β-carboline scaffold, and which has been proven to exhibit diverse biological functions. During the course of our research for highly active compounds from natural products, the pityriacitrin have also been isolated and identified from a Chinese Burkholderia sp. NBF227. So, in order to explore the potential functional molecules, a series of β-carboline analogues derived from pityriacitrin were designed and synthesized, and their in vitro cytotoxic activities against SGC-7901, A875, HepG2, and MARC145 cell lines were evaluated. The results demonstrated that some of these β-carboline derivatives exhibited moderate to good cytotoxic activities, especially, compound 9o with a special sulfonyl group presented the highest inhibitory activities against all tested cell lines with the IC₅₀ values of 6.82 ± 0.98, 8.43 ± 1.93, 7.69 ± 2.17, 7.19 ± 1.43 μM, respectively, which might be used as lead compound for discovery of novel cytotoxic agents.