Study On The Terpenoid Constituents Of Agarwood, A Mongolian Medicinal Herb

Syringa pinnatifolia Hemsl.(SP),an endemic Chinese species belonging to the Oleaceae family,is mainly distributed in the Helan Mountain region between Ningxia and Inner Mongolia provinces of China.The peeled roots,stems,and twigs,called 'Shanchenxiang' in Chinese,is one of the most traditional Mongolian folk medicines for the treatment of cardiovascular symptoms,asthma,pain,and fever,and this remedy has been used for hundreds of years.SP is traditionally used as a powder,while its purple resins in the wood are believed to contribute to its therapeutic effects.Previous pharmacological research revealed that SP essential oils,which containing mainly zerumbone(humulane-type sesquiterpenoid),showed a cardioprotective effect against acute myocardium ischemia(AMI)in rats.In addition,the EtOH extract of SP,which mainly contain sesquiterpenoids and lignans with moderate to low polarities,also showed anti-AMI effects in mice.Consequently,although terpenoids and especially sesquiterpenoids are rarely reported from SP,they are among the constituents with prominent anti-AMI effects.Therefore,aiming to determine the constituents of SP with anti-AMI efficacy,a phytochemical investigation using 1H NMR-guided fractionation of SP stems and evaluation of pharmacological effects against AMI was conducted herein.Firstly,the review section summarizes the previously reported humulane-type sesquiterpenoids,classifying them in three types,and describes their sources and biological activities,hopefully to provide evidences for the elucidation,pharmacological activity screening and illustrating their mechanisms.The phytochemical investigation was launched via 1H NMR-guided fractionation of SP stems,leading to the isolation of 62 compounds including 40 new compounds and 11 analogues isolated from the genus for the first time.These structure were established using IR,UV,MS,and NMR spectroscopic data.The absolute configurations of the compounds were determined using X-ray diffraction,a modification of Mosher's method,and calculated ECD methods.There are 47 terpenes isolated from the peeled stems of SP,consisting of 29 sesquiterpenoids 1-22(seven pair of enantiomers),six eremophilane dimers(23-28),seven dimeric sesquiterpenoid-lignan derivatives(29-35),and five triterpenoids(36-40).These sesquiterpenoids isolated from SP stems possess five structure skeletons,namely,a rare 2,2,5,9-tetramethylbicyclo[6.3.0]-undecane(1),humulane-type(2-8,11-16),eremophilane-type(19-22),and caryophyllene-type sesquiterpenoids(9,10,17),and an acyclic aldehyde(18).Elsewhere,15 other types of constituents consisting of 13 lignans(41-53),a phenylpropanoid(54),and one phenolic compound(55)were isolated,due to the practical difficulty of separating the two portions of sesquiterpenoids and lignans clearly.Pharmacological evaluation in vitro of these compounds were tested according to the anti-AMI effects of SP and cytoxic activities against HepG2 cells of humulane-type sesquiterpenoids.Compounds 6a,7,and 13 showed protective effects against hypoxia-induced injury to H9c2 cells at a concentration of 40?M,and 5b-7,13,and 15 inhibited nitric oxide(NO)production in lipopolysaccharide(LPS)-induced RAW 264.7 macrophage cells with IC50 values ranging from 13.6-70.6 ?M.Moreover,these compounds decreased the TNF-? and IL-6 levels in RAW 264.7 macrophage cells in a concentration-dependent manner at 20-80?M.Compounds 13,14,20 and 21 showed cytoxic activities against HepG2 cells with IC50 values of 34.81,14.12,34.41,and 40.86 ?M,respectively?Briefly,as a part of the systematic research on illustrating the anti-AMI components of SP,this paper herein describes the isolation and structural determination of 62compounds and the biological evaluations of their protective effects against hypoxia injury to H9c2 cells,abilities to inhibit NO production in LPS-induced RAW 264.7 cells,and cytoxic activities against HepG2 cells.These findings provide a foundation for illustrating the anti-AMI components of SP,and are helpful on the elucidation for the absolute configurations of humulane-type sesquiterpenoids.