Study On The Secondary Metabolites Of Pittosporum Subulisepalum And Their Biological Activities

The secondary metabolites and their biological activities of Pittosporum subulisepalum（P.subulisepalum）were studied.Various chromatographic methods and techniques,such as silica/RP-silica column,Sephadex LH-20,preparation HPLC,et al,were applied to isolate the secondary metabolites from P.subulisepalum.The planar and stereo structures of the isolates were identified by comprehensive use of 1D/2D NMR,HRESIMS,IR,UV,CD,SC-XRD and other spectral analysis techniques.Finally,a total of 33 compounds were isolated and elucidated from this plant,including 22 new sesquiterpenoid glycosides with various skeleton types and11 other known compounds（three triterpenoids,four lignans,two phenylpropanoids and a benzaldehyde derivative）.With respect to the structure scaffolds,P.subulisepalum possessed various types of secondary metabolites,and sesquiterpenoid glycosides are the main components,including twelve eudesmane-type（pitsubcoside A-L（1-12））,seven cadinane-type（pitsubcoside M-S（13-19））,one elemane-type（pitsubcoside T（20））,one carabrane-type（pitsubcoside U（21））and one unknown skeleton（pitsubcoside V（22））.All the compounds were submitted to the screening for antibacterial activities.Above all,the antibacterial activities against four Gram-positive bacteria（Staphylococcus aureus,Methicillin-resistant Staphylococcus aureus,Bacillus cereus and Bacillus subtilis）and four Gram-negative bacteria（Escherichia coli,Pseudomonas solanacearum,Erwinia carotovora and Pseudomonas syringae pv.actinidiae）showed that the sesquiterpenoid glycosides from P.subulisepalum displayed obvious antibacterial effects with the minimum inhibitory concentrations（MICs）among 25-100μM,whearas the phenylpropanoids,lignans and oleanane-type triterpenoids had relatively weak antibacterial activities with MICs above 100μM.Among those,compound 20 exhibited strong inhibitory activities against S.aureus,E.coli and P.syringae pv.actinidiae with MIC 25μM and relatively higher MIC 50μM against B.cereus.Also,compounds 3,6 and 7 showed certain growth inhibitory effects against these four bacteria with MICs below 100μM.Meanwhile,anti-neuroinflammatory activities of all the sesquiterpenoid glycosides were evaluated by constructing a mouse microglia BV-2 cells inflammatory model induced by LPS,which manifested that some showed significant activities against the LPS-induced NO release in BV-2 cells.Among those,compound 20 exhibited the highest activity(IC₅₀=5.96μM),and compounds 3,8,13 and 21 also showed strong activities with IC₅₀ of 11.15,8.79,16.29 and8.76μM,respectively.