Antimicrobial activities of crude extract, Caulindole D, a mixture of Caulindole E and F, Pinocembrin and an Oxyheptanoid (Clestochlamic acid) from stem bark of Isolona cauliflora and Cleistochlamys krikii on Pseudomonas phaseolicola, Fusarium solani, Botryodiploida theobromae, Aspergillus niger and Aspergillus flavus have been investigated. An in vitro bioassay test showed that the crude dichloro-methane extract from C. krikii and a very strong antimicrobial property. The pure compound had strong to moderate inhibitory effect on Pseudomonas syringae pv. phaseolicola and Botryodiplodia theobromae. The pure compounds from Cleistochlamus krikii had more pronounced inhibitory activities than the pure compounds from Isola cauliflora. At lower concentration of 100-200 ppm, the crude extract of Caulindole, mixture of Caulindole E and F, Pinocembrion and Oxyheptanoid had effect on most of the investigated plant pathogens. Higher concentration of 500-1000 ppm had moderate to weak effect on the Aspergillus spp.