Antimicrobial Activity of the Secondary Metabolites Isolated from a South African Red Seaweed, .

South Africa's highly diverse marine biota includes several endemic marine red algae of the genus. Cryptic species and morphological variability make the taxonomy of plant challenging, and a record of the secondary metabolites isolated from South African spp. can be used to assess their chemotaxonomic significance. In addition, the rapid development of resistance against antibiotics, coupled with the inherent ability of seaweeds to resist pathogenic infection, supported this first phycochemical investigation of J. Agardh. A new tricyclic keto-cuparane () and two new cuparanes () were obtained alongside known acetogenins, halo-chamigranes, and additional cuparanes. These compounds were screened against , , , , and , with exhibiting excellent activity against the Gram-negative (minimum inhibitory concentration (MIC) 1 μg/mL) strain.