ANTIBACTERIAL PROPERTY TESTING OF TWO SPECIES OF TROPICAL PLANT LASIANTHUS (RUBIACEAE).

Two tropical plant species, Lasianthus pilosus and Lasianthus stipularis are used in traditional medicine but there have been no published studies of the extracts of these plants against bacteria. In this study, we aimed to determine the antimicrobial activities of the above two plants against two gram-positive and seven gram-negative bacterial strains to determine the potential of these two plant species for possible antimicrobial drug development. The antibacterial activities of the lipophilic extracts of these plants were evaluated by disk diffusion and broth microdilution methods. The zone diameters and minimum inhibitory concentrations (MIC) for these plant extracts exhibited their highest antibacterial activity against Pseudomonas aeruginosa, followed by Staphylococcus aureus and Acinetobacter baumannii, respectively. The MIC of these extracts against P. aeruginosa (ATCC 37166 and ATCC 27853) varied from 50 to 200 µg/ml. Thin layer chromatography and detection using different specific reagents revealed the presence of terpenoids, phenolic compounds and iridoid. Cell lysis due to the effect of the lipophilic extracts of these tested plants was demonstrated using scanning electron microscopy. In conclusion, the bioactive compounds of these plants should be studied further to develop potential antimicrobial agents.

Correlation of camptothecin-producing ability and phylogenetic relationship in the genus Ophiorrhiza.

Camptothecin (CPT) is an essential precursor of semisynthetic chemotherapeutic agents for cancers throughout the world. In spite of the rapid growth of market demand, CPT raw material is still harvested by extraction from Camptotheca acuminata and Nothapodytes foetida because its total synthesis is not cost-effective. In this study, we examined eight species of the genus Ophiorrhiza (Rubiaceae) from Thailand as novel alternative sources of CPT. CPT and/or 9-methoxy camptothecin (9-MCPT) were detected at different amounts in the leaf and root extracts of five species. We found that the CPT production ability of Ophiorrhiza spp. in Thailand was related mainly to species, not habitat. Chloroplast MATK and nuclear TOPI genes of eight species were investigated and compared with those of other Ophiorrhiza sequences from GenBank in order to classify and study the evolution in this genus. The molecular phylogenetic trees of both separated and combined MATK and TOPI nucleotide sequences revealed a major clade of Ophiorrhiza taxa correlated with production of CPT and its derivatives. Several amino acid markers of CPT- or 9-MCPT-producing Ophiorrhiza plants were also suggested from the alignment of TopI amino acid sequences. Our findings suggest that genetic factors play an important role in determining the CPT- and 9-MCPT-producing properties of Ophiorrhiza plants. Consequently, MATK and TOPI gene sequences could be utilized for the prediction of CPT and 9-MCPT production ability of members of Ophiorrhiza.