Bioactivity of leaves of Macaranga species in tropical peat swamp and non-peat swamp environments

Very few studies have been reported on the chemical properties of peat swamp plants compared with their non-peat swamp counterparts. In this study, the total phenolic content, antioxidant activity and antibacterial activity of fresh Macaranga gigantea, M. hosei, M. hypoleuca, M. kingii, M. pruinosa and M. triloba leaf extracts from four tropical peat swamp forests and three non-peat swamp forests were measured and compared. Total phenolic content was measured by the Folin-Ciocalteu assay. Antioxidant activity was determined using the 1,1-diphenyl-2-picrylhydrazyl free radical scavenging and ferric reducing power assays, while disc-diffusion technique was used to determine the antibacterial properties. Reversed-phase-high-performance liquid chromatography methods were used to identify and quantify the concentrations of phenolics. Antioxidant properties of leaf extracts from peat swamp forest species were 42 to 60% higher than those of the same plant species from non-peat swamp forest. However, no significant differences were observed for samples collected from within the same environmental conditions. No significant differences were found in antibacterial activities between peat swamp and non-peat swamp samples. The results suggest that trees in peat swamp forests are producing higher levels of phenolic compounds in response to extreme conditions.