Lyngbyabellin Q, an Antimalarial Cyclic Peptide, and Its Acyclic Analog from a Cyanobacterial Biomat Dominated by <i>Moorena</i> sp.

Two new lyngbyabellin analogs, Q (<b>1</b>) and R (<b>2</b>), were isolated from a marine cyanobacterial biomat dominated by <i>Moorena</i> sp. Their structures were established primarily through a combination of spectroscopic analyses and degradation reactions. Lyngbyabellin Q (<b>1</b>) inhibited the growth of HeLa cells and disrupted actin dynamics. In addition, lyngbyabellin Q (<b>1</b>) exhibited potent antimalarial activity with an IC₅₀ value of 22 nM, and a new structure-activity relationship enhancing selectivity for the growth inhibition of <i>Plasmodium falciparum</i> over mammalian cells was identified.