Study On Chemical Constituents Of Meliae Cortex

Meliae Cortex is the dried root bark and cortex of the plant Melia azedarach L.Meliae Cortex was included in the Pharmacopoeia of People's Republic of China as an anthelmintic drug.With researching and discoverying over the years,there are a variety of chemical constituents in Meliae Cortex,and many other pharmacological effects have also been confirmed in addition to expelling parasite.In this study,it was carried out that the systematic investigation on the chemical consitituents of the 75%ethanol extraction of Meliae Cortex.By using silica gel column chromatography,gel chromatography,semi preparative HPLC and other separation and purification methods,prosapogenins were obtained by hydrolysis reaction with alkaline at the same time.Twenty-two compounds were identified.Nineteen of them were separated and determined from the extraction site of the ethyl acetate layer.They were toosendansin A?1?,toosendansin D?2?,7?-benzoyl-12?-O-methylvolkensin?3?,7?-tigloyloxyl-12?-O-methylvolkensin?4?,1a-benzoyloxy-3a,7a-dihydroxy-12a-ethoxy nimbolinin?5?,1a-tigloyloxy-3a,7a-dihydroxy-12?-ethoxynimbolinin?6?,1?-benzoyloxy-3?-acetoxyl-7?-hydroxyl-12?-ethoxylnimbolinin?7?,meliatoosenin L?8?,1?,3?-dihydroxyl-7?-tigloyloxy-12?-ethoxylnimbolinin?9?,1?,7?-ditigloyloxy-3?-acetoxyl-12?-ethoxyl-nimbolinin?10?,12?-O-ethyl-nimbolinin B?11?,3?-O-?-D-xylopyranosyl-?1?3?-?-L-rhamnopyranosyl-?1?2?-?-L-arabinopyranosyl-hederagenin-28-O-?-L-rhamnopyranosyl-?1?2?-?-D-xylopyranosyl-?1?4?-?-D-glucopyranoside?12?,3?-O-?-L-rhamnopyranosyl-?1?2?-?-L-arabinopyranosyl-11?-methoxy-hederagenin-28-O-?-L-rhamnopyranosyl-?1?2?-?-D-glucopyranosyl-?1?4?-?-D-glucopyranoside?13?,3?-O-?-D-xylopyranosyl-hederagenin-28-O-?-D-glucopyranosyl-?1?6?-?-D-glucopyranoside?14?,3?-O-?-D-xylopyranosyl-22?-hydroxyl-hederagenin?15?,12?-O-methyl-1?-O-deacetyl-nimbolinin B?16?,12?-O-ethyl-1?-deactylnimbolinin B?17?,6?,11?-diacetoxygedunin?18?,3'-O-methylcatechin 7-O-?-D-glucopyranoside?19?.The products obtained by alkaline hydrolysis of compounds 12,13 and 14 are:3?-O-?-D-xylopyranosyl-?1?3?-?-L-rhamnopyranosyl-?1?2?-?-L-arabinopyranosyl-hederagenin?12a?,3?-O-?-L-rhamnopyranosyl-?1?2?-?-L-arabinopyranosyl-11?-methoxy hederagenin?13a?,3?-O-?-D-xylopyranosyl-hederagenin?14a?.Compounds 2¹9 were obtained from Meliae Cortex for the first time,and compounds 12¹5 were identified as four new compounds.Compounds 12a,13a and 14a were identified as artefacts.The preliminary pharmacological activities of compounds 1¹7 and three prosapogenins?12a?13a?14a?were studied by the method of MTT.It was found that compounds 12a and 13a,which there is a free carboxyl at C-28 position,had strong cytotoxicity to human hepatoma HepG2 cells and human glioma U-87MG cells,and compound 15 had weak cytotoxicity to these two kinds of cells.Compound 12a showed the most potent cytotoxicity to these two cancer cell lines with IC₅₀ at 6.63?mol/L and8.45?mol/L,respectively.The other three sapogenins which had double sugar chains at C-3 and C-28 position,and one prosapogenins which had a simple sugar at C-3 position all had no cytotoxicity to the cells.While,the limoniods isolated from the plant had no cytotoxicity either.The results of the experiments further reveal the structure-activity relationship of saponins.It is a necessary condition that a free carboxyl group is at C-28position to the hederagenin.Hydroxyl substitution at C-22 site may be a reason for enhancing the toxicity of hederagenin to tumor cells.Further confirming by consulting the literature and combining the experimental data of the subject,salannin-type and C-seco-nimbolinin-type limoniods had no cytotoxicity.Innovations and significance:1.In this study,we study on the extraction site of ethyl acetate of the alcohol extract of Meliae Cortex.Twenty-two compounds were identified.Among them,there are three prosapogenins.Compounds 2¹9 were obtained from Meliae Cortex for the first time.There are four new oleanane-type triterpenoid saponins?hederagenin or derivative?,a flavonoids,a salannin-type limoniods,a tirucallanes-type triterpenoid,a gedunin-type limoniods and eleven C-seco-nimbolinin-type limoniods.2.We obtained four new triterpenoid saponins from Meliae Cortex for the first time.By searching the literature,it is the first time that triterpenoid saponins were found in meliaceae.The reason may be that there is few study on the water soluble constituents of Meliae Cortex.The study is for the first time that four new triterpenoid saponins were isolated and purified from the large polar segment of the ethyl acetate extract from the alcohol extract of the plant,which provides new information for the study of the chemical composition of the Melia L.in the future,especially in the large polar segment.3.We selected monomer compounds obtained from Meliae Cortex and prosapogenins obtained by alkali hydrolysis reactions.Through the preliminary screening of anti-tumor activity,we found two prosapogenins which had strong cytotoxicity and a triterpenoid saponins which had weak cytotoxicity.The results of the experiment further reveal the structure-activity relationship of saponins,and prove the feasibility to increase the cytotoxicity of the tumor cells by alkaline hydrolysis reactions to the triterpenoid saponins.At the same time,it proves that gedunin-type and C-seco-nimbolinin-type limoniods have no cytotoxicity.Finding in various structural types of antineoplastic constituents of Meliae Cortex,provides a new idea for the further medicinal materials as anti-tumor medicine research and development.