Studies On The Chemical Constituents From The Fruits Of Garcinia Bracteata And The Seeds Of Nigella Glandulifea And Their Bioactivities

Garcinia bracteata C.Y.Wu ex Y.H.Li belongs to the genus Garcinia of the Guttiferae family.Its fruits are edible.In this paper,using modern chromatographic separation techniques combined with modern spectroscopy and quantum computational chemistry methods,26 compounds（1-9,10a,10b,11,12,13a,13b,14-1,14-2,15,16,17a,17b,18a,18b,19a,19b,20）were separated and identified from the 95%ethanol extract of the fruits of Garcinia bracteate,which contained eight polycyclic polyprenylated acylphoroglucinols derivatives（1-8）,three benzophenone derivatives（9-11）,three new skeleton xanthones（12,13a,13a?）,four caged polyprenylated xanthones（14-1,14-2,15,16）and seven classic polyprenylated xanthones（17a,17b,18a,18b,19a,19b,20）.There are nine new carbon skeleton compounds（1-5,7,12,13a,13a?）and eight new compounds（6,8,14-1,14-2,17a,17b,18a,18b）.These new compounds and new carbon skeleton compounds were named as garcibractinone C（1）,garcibractinone D（2）,garcibractinone E（3）,garcibractinone F（4）,garcibractinone G（5）,garcibractinone H（6）,garcibractinone I（7）,garcibractinone J（8）,epi-garcibractinone K（12）,（-）-garcibractinone K（13a）,（+）-garcibractinone K（13a?）,（-）-garcibractinone L（14-1）,（+）-garcibractinone L（14-2）,（-）-garcibractinone M（17a）,（+）-garcibractinone M（17b）,（-）-garcibractinone N（18a）,（+）-garcibractinone N（18b）.Compound 1 is a PPAPs with novel 6-oxatricyclic[7.4.1.1^1,11]pentadecane skeleton;and compound 3 is a PPAPs with 5,8-dioxatricyclic[4.3.0.2.0^3,7]undecane skeleton.Compounds 2 and 4 are obtained by the cleavage of phloroglucinol core of compounds 1 and 3 through retro-claisen reaction.Compound 4 contains4,6,12-trioxatricyclo[6.4.0.0^1,5]dodecane skeleton.Compound 5 is the first degraded seco-BPAPs with 3-oxabicyclo[5.3.0]decane skeleton.Compound 6 is cyclized by isoprenyl side chain to form the first example of PPAPs possessing11-oxatricyclic[4.3.1.1^4,10]undecane skeleton with a tetrahydrofuran ring.Compound7 possesses a fascinating 9-oxabicyclo[6.2.1]undecane skeleton.Compounds 12,13a,13a?has a novel polyprenylated xanthones skeleton with 7-oxatricyclo[3.3.1.0^6,9]n-onane.Compound 14-1 and 14-2 are caged polyprenylated xanthone containing4-oxatricyclo[4.3.1.0^3,7]decane skeleton with hemiketal carbon at C-6.The novel skeletons?PPAPs（1-5,7）are produced by the retro-claisen reaction,which cause the phloroglucinol core to cleave.In addition,compound 5 is formed by oxidation and degraded in the biosynthetic pathway.These novel polyprenylated xanthone skeletons 12,13a and 13a?are produced by decarbonation.The discoveries of new skeleton compounds such as compounds 1,2,3,4,5,7,12,13a and 13a?reveal the metabolic diversities of PPAPs and polyprenylated xanthones of Garcinia bracteate,which provided a certain scientific basis for the exploration of PPAPs and polyprenylated xanthones in fruits.Nigellae Semen is the dried and mature seeds of Nigella glandulifea Freyn et Sint which belongs to the genus Nigella of the Ranuncualceac family.It is a traditional Uyghur medicine in our country which can be used to treat tinnitus,forgetfulness,and less amenorrhea,hot shower,stone shower,etc.In this paper,the 50%ethanol extract of the seeds of Nigella glandulifea Freyn et Sint was systematically separated and purified.Eleven compounds were separated.Eleven compounds were identified by modern spectroscopy techniques such as nuclear magnetic resonance,mass spectrometry combined with quantum chemical ECD and NMR calculations,including three triterpene saponins（21-23）,two dolabellane diterpenes（24-25）,one acyclic sesquiterpene（26）,one alkaloid（27）,one lignan（28）,two phenolic components（29,30）and one long-chain fatty acid（31）.Among them,there are two new compounds（25,26）which were named as 8-denicotinoylnigellamine A₁（25）and3,7,11-trimethyldodec-10-ene-1,6,7-triol（26）,respectively.To clarify the anti-diabetic mechanism of the seeds of Nigella glandulifea Freyn et Sint,we studied the toxic effects of 10 compounds（21-30）on human hepatocarcinoma cells（Hep G2）by the CCK-8 method and further evaluated their potential protective effects on insulin-resistant human hepatocarcinoma cell model（Hep G2/IR）in vitro.The results showed compounds 21,22,23,24,27,28,30 can improve Hep G2/IR glucose metabolism disorder.Therefore,the anti-diabetic activity of Nigellae Semen is the result of the joint action of various structural metabolites such as alkaloids,dolabellane-type diterpenes,lignans,triterpene saponins and phenolic components.The antiproliferative and anti-inflammatory activities of compounds 21-30 were evaluated.Compound 22 displayed certain inhibitory activities against three human cancer cell lines（Hep G2,T98,A549）with IC₅₀ of 14.76±0.44,13.53±0.17,12.96±0.41μM respectively.Compound 21 only exhibited inhibitory activity against the A549 human cancer cell line with IC₅₀ of 9.05±0.32μM.Moreover,compounds21,22 and 28 also exhibited significant inhibitory effects on nitric oxide production by lipopolysaccharide（LPS）-activated macrophage 264.7 with IC₅₀ values of9.98±0.26,9.13±0.10 and 18.99±0.46μM respectively.Therefore,28-COOH played a key role in maintaining the anti-tumor and anti-inflammatory activities of hederagenin saponins.Saponins bearing anα-L-rhamnopyranosyl-（1→2）-α-L-arabinopyranosyl moiety at 3-position display certain anti-inflammatory potency.The experimental results were consistent with the literature reports,and these results would provide a scientific reference for elucidating the pharmacodynamic mechanism of Nigella sativa L.in exerting the anti-tumor cell proliferation and anti-inflammatory activities.