Secondary metabolites from leaves and branches of Podocarpus fleuryi Hickel and their antibacterial activities

ObjectiveThe present study was conducted to analyze and identify the chemical composition of the volatile oils extracted in leaves and branches of Podocarpus fleuryi Hickel. The antibacterial activities of the volatile oils and methanol extracts were tested against seven different bacteria. This study would provide the potential foundation for the development and utilization of P. fleuryi resources. MethodThe volatile oils were extracted by hydro-distillation from leaves and branches of P. fleuryi and the chemical compositions of the essential oil were analyzed by gas chromatography-mass spectrometry(GC-MS). The relative percentages of different chemical components were measured by peak area nor-malization. Inhibition zone method and TLC-MTT-bioautography were used to detect the inhibitory activities of volatile oils extracted from leaves and branches of P. fleuryi and methanol extracts against the tested bacteria. ResultThe yields of volatile oils in leaves and branches were 0.104% and 0.078%, respectively. Forty-five components were identified from the volatile oils in leaves, accounting for 92.63% of total volatile components. The major constituents included(1R)-α-pinene (34.50%), germacrene B (22.82%), germacrene D (5.46%), viridiflorene (4.74%) and α-gurjunene (3.15%). Forty-four components were identified from the volatile oils in branches, accounting for 95.51% of total volatile compo-nents. The major constituents included (1R)-α-pinene (43.86%), δ-cadinene (7.93%), l-caryophyllene (4.92%), (3aS,3bR,4S,7R,7aR)-7-methyl-3-methylidene-4-(propan-2-yl)octahydro-1H-cyclopenta1,3cyclopropa1,2ben-zene (4.91%), 2-isopropyl-5-methyl-9-methylene4.4.0dec-1-ene (3.72%), copaene (3.68%), γ-cadinene (3.60%) and cyclosativene(3.04%). The volatile oils in leaves and branches showed certain inhibitory activities to the tested bacte-ria, but the differences were not obvious. The volatile oil in leaves showed the strongest inhibitory activity against A-grobacterium tumefaciens and the inhibition zone diameter was 9.0 ±0.0 mm. While the branches volatile oil showed strongest inhibitory activities against Staphylococcus haemolyticus and Pseudomonas syringae, and inhibition zone diame-ters were both 8.3 ±0.6 mm. The methanol extracts from the leaves and branches showed sound inhibitory activity to the tested bacteria except for Ralstonia solanacearum, and the inhibitory activities of methanol extracts from leaves was stronger than that of methanol extracts from branches. ConclusionThe antibacterial substances in leaves and branches of P. fleuryi Hickel are mainly non-volatile substances, and can be developed as natural antibacterial substance resources.