Studies On Chemical Constituents And Their Bioactivities Of Medicinal Parts Of Melia Toosendan From Guizhou Province

Objective:In this study,we systematically investigated the chemical compositions and biological activities of the Et OAc extract from the bark and fruit of Melia toosendan in Guizhou Province,with the aim of identifying small molecular compounds with novel structures and potent activities,and providing a basis for the development and utilization of traditional medicinal plant resources in the region.Methods:The barks and fruits of Melia toosendan were collected from Guizhou Province,dried,and crushed before undergoing extraction by reflux with 95%ethanol.The resulting extract was concentrated with Et OAc to obtain the ethyl acetate extract of toosendania bark and fruit.Monomer compounds were then purified and isolated using various methods,including reverse ODS chromatography,silica gel column chromatography,Sephadex LH-20,and semi-preparative HPLC.The structures of the monomer compounds were identified using spectroscopy methods,such as 1D(¹H,¹³C)NMR,2D（HMBC,HSQC,¹H-¹H COSY,or NOESY）NMR,HR-ESIMS,IR,and UV.The absolute configurations of new compounds were confirmed by ECD calculations and single crystal X-ray crystallography.The natural compounds were further evaluated for antibacterial and cytotoxic activities.Results:A total of 85 compounds were identified from the ethyl acetate extract of the bark of M.toosendan,consisting of 77 triterpenoids,including sixty-four tirucallane types,ten damarane types,two limonin types and one alkyl oleanate type,as well as five steroid compounds and three other classes.Of these,27 structures（1-27）,including eighteen tirucallanes,four damaranes,two limonins,and three steroids,were newly discovered,and the structures of compounds 1,7,and 15 were confirmed by the single crystal X-ray crystallographic experiment.This plant yielded a novel collection of 32 monomeric compounds,which were isolated for the first time.Moreover,the ethyl acetate extract of the fruits of M.toosendan in Guizhou Province yielded 39 natural products,including twenty-nine limonin triterpenes,six tirucallane triterpenes,one lupinane triterpene,and three steroids,with fourteen new structures（86-99）,comprising eleven limonin triterpenes,two tirucallane triterpenes,and one steroid.Furthermore,a total of 15 compounds were isolated from this plant for the first time.Several compounds,including 11,41,44,45,46,55,69,and 78,showed significant antibacterial activities against Pseudomonas solanum,Clostridium perfringens,and Bacillus subtilis,with minimum inhibitory concentrations ranging from 47μg/m L to 97.6μg/m L.Secondly,compound 109 had significant inhibitory effects on Botrytis cinerea with EC₅₀ of 9.8μg/m L,while compound 104 showed the EC₅₀ value of 20.1μg/m L on Alternaria solani,outperforming Chlorothalonil（11.4and 28.3μg/m L）.In addition,compounds 15 and 88 exhibited weak cytotoxic activity against three breast cancer cell lines（MDA-MB-231,MCF-7,and 4T1）,with IC₅₀values ranging from 12.1μM to 23.2μM.Conclusions:This paper provides a systematic study of the chemical compositions and biological activities of the medicinal properties of the bark and fruit of M.toosendan from Guizhou Province,employing modern phytochemical separation methods.The study reveals that the chemical constituents of M.toosendan are primarily triterpenoids,with tirucallane triterpenoids being the main component of its antibacterial activity,and limonin triterpenoids being the main component of its anti-viral activity.These findings provide a scientific and theoretical basis for further exploration and utilization of this plant.