Antiproliferative Alkaloids From The Bulbs Of Hymenocallis Littoralis(Jacq.)Salisb.

Hymenocallis littoralis（Jacq.）Salisb.,which is also called‘spider lily’because of the special shape of its flowers,is a bulbous herbaceous plant belonging to the family Amaryllidaceae.The genus Hymenocallis is native to tropical regions of the Americas and the West Indies,originally introduced and cultivated by Fujian and Guangdong provinces of China as a landscape plant.From the perspective of new drug discovery,H.littoralis has been reported to possess large amounts of Amaryllidaceae alkaloids,and these alkaloids have promising multiple biological effects including antitumour,anti-inflammatory,antivirus and anti-parasite activities.In this study,the air-dried bulbs of H.littoralis were extracted with 75%ethanol and the combined extracts were concentrated under reduced pressure.The ethanol-free suspension was first defatted three times with the same volume of cyclohexane.Then,the aqueous suspension was adjusted to p H 2 with hydrochloric acid（10%）,and the acidified aqueous suspension was extracted three times with the same volume of ethyl acetate to remove the nonalkaloid fraction.After that,the aqueous suspension was adjusted to p H 10 with ammonia spirit（25%）,and the basified aqueous suspension was extracted three times with the same volume of ethyl acetate to acquire the total alkaloids.The total alkaloids were separated and purified by silica gel column,ODS,Sephadex LH-20 and preparative HPLC.The structures were elucidated on the basis of various spectroscopic methods（UV,IR,MS,NMR,ECD）.The alkaloids were identified as:6-oxo-12β-hydroxy-5,6-dihydroplicane（1*）,6-oxo-12β-methoxy-5,6-dihydroplicane（2*）,6-oxo-5,6-dihydroplicane（3）,5,6-dihydroplicane（4）,12β-hydroxyplicane（5*）,（+）-plicane（6）,N-hydroxyethyl-11,12-seco-5,6-dihydroplicane（7*）,（-）-secoplicamine（8）,5,12-dehydro-11,12-seco-5,6-dihydroplicane（9*）,（3S,4a S,6a S,12b S）-3,11-dimethoxy-5-methyl-4,4a,5,6-tetrahydro-8H-isochromeno[3,4-c]indole-6a,10（3H）-diol（10*）,6-（2-methylaminophenyl）-N-methyl-N-[2-（4-hydroxyphenyl）-ethyl]-piperonylamine（11*）,tazettine（12）,jonquailine（13）,6-O-methylpretazettine（14）,3-epimacronine（15）,egonine（16）,tazettamide（17）,N-methyl-5,6-dihydroplicane（18）,obliquine（19）,haemanthamine（20）,haemanthidine epimer B（21）,haemanthidine epimer A（22）,lycorine（23）,dihydrolycorine（24）,5,6-dihydrobicolorine（25）,N-methylcrinasiadine（26）,trispheridine（27）,zephycandidine A（28）,lycoranine D（29）,hymenolitatine A（30）,5-Methyl-5H-[1,3]dioxolo[4,5-b]carbazole（31）,narciclasine-4-O-β-D-glucopyranoside（32）,4-O-β-D-glucopyranosyl-trans-dihydronarciclasine（33）,β-adenosine（34）,N-[2-（4-hydroxyphenyl）]ethylacetamide（35）,and nicotinamide（36）.Compounds 1-33 are Amarylliaceae alkaloids and 34-36 are some simple alkaloids.Compounds 1,2,5,7,9-11 are seven previously undescribed Amarylliaceae alkaloids.Compounds 3,4,17 and 31 were isolated and identified for the first time from natural origin.The isolated alkaloids were screened for antiproliferative activity against four human tumour cell lines（Hep G2,He La,SPC-A-1,Fa Du）through MTT assay,and Compounds 11,13 and 14 exhibited potent cytotoxicity.Compound 11 had an obvious inhibitory effect against Hep G2 cells,with an IC₅₀ value of 22.97±3.99μM.Compounds 13 and 14 were a pair of epimers at C-6,and they showed quite different cytotoxicity towards the four human tumour cell lines,especially in He La cells.Therefore,cell morphological assessment,flow cytometric analysis,Western blot analysis,clone formation and scratch wound assays were utilized for Compounds 11,13 and 14,which had antiproliferative effects on the Hep G2 and He La cell line via induction of apoptosis in a dose-dependent manner.In addition,the alkaloids also possessed the potential to inhibit tumour cell migration.