Studies On Chemistry And Bioactivities Of The Brown Alga Pachydictyon Coriaceum

Brown algae of the Pachydictyon coriaceum（genu Pachydictyon,family Dictyotaceae,order Dictyotales and class Phaeophyceae）,found in all oceans and seas as well as almost all latitudes,mostly in tropical and subtropical regions,are well-known for their ability to biosynthesize an astonishing variety of structurally unusual secondary metabolites.Secondary metabolites from this alga are sesquiterpenes,diterpenes,alkaloids,fatty acids,and sterols,of which diterpenes are predominant substances that possess unique structural features and show a range of potent biological activities.These usual strucgural and biological features have attracted great attention from marine natural product chemists and pharmacologist.During the course of our search for bioactive secondary metabolites,we have collected P.coriaceum from Nanji Island Zhe Jiang Province.In this thesis,we have systematically studied on the chemical constituents and biological activity of this alga.The fresh algal material was exhaustively extracted with 95%EtOH.The resultant extracts were suspended in H₂O and then partitioned with Et₂O.The Et₂O-soluble portions were repeatedly subjected to silica gel and Sephadex LH-20 column chromatography followed by semipreparative C₁₈8 silica HPLC purification,yielding31 compounds,including 4 sesquiterpenes（1⁴）,15 diterpenes（5¹9）,2 sterols（20and 21）,3 phthalates（22²4）,7 fatty acids（25³1）.Among these compounds,compound 6 is new.Their structures including relative stereochemistry were elucidated on the basis of extensive spectroscopic analysis（NMR,MS,IR,UV,and optical rotation）and comparison with those reported data in the literature.Literature checking revealed that secondary metabolites from P.coriaceum showed diverse activities,such as cytotoxic,antimicrobial,antifeedant,and antiinflammatory etc.Because the on enzyme inhibitory activity for metabolites from the alga has not been reported,The PTP1B inhibition and enzyme inhibition against receptor tyrosine kinases c-Met,ALK,and RET of the isolated compounds were evaluated in our experiments.At present,the evaluation of PTP1B inhibitory and enzyme inhibitory activities of the compounds from P.coriaceum have been finished.As a result,compounds 1,8,9,14,and 16 exhibted different levels of inhibitory activity against PTP1B,and only compound 4 showed weak inhibitory activity against RET with an IC₅₀0 value of 10.9μM.However,all of tested compounds exhibited no inhibition against receptor tyrosine kinases c-Met and ALK.