An Efficient Cationic Cyclization Approach for the Construction of Labdane Diterpenoid Decalin Ring Skeleton

An effective approach for the construction of the decalin ring skeleton of labdane diterpenoids was developed based on a key biomimetic cationic polyene cyclization of an epoxy allylsilane precursor. The synthetic approach demonstrated here would be useful in the enantioselective and diastereoselective total synthesis of natural labdane diterpenoids in general.

Two Labdane Diterpenes from Leonurus heterophyllus

Two new labdane diterpenoids named heteronone A （1） and heteronone B （2） were isolated from the aerial parts of Leonurus heterophyllus Sweet. Their structures were established by various spectroscopic means, and the structure of heteronone A is confn-med by X-ray diffraction analysis.

New di-spirocyclic labdane diterpenoids from the aerial parts of Leonurus japonicus

Phytochemical investigation on the ethanol extract of a well-known medicinal herb Leonurus japonicus,led to the separation of 18 labdane type diterpenoids(1-18).Through comprehensive spectroscopic analyses and quantum chemical calculations,these compounds were structurally characterized as six new interesting 5,5,5-di-spirocyclic ones(1-6),two new(7 and 8)and six known(13-18)interesting 6,5,5-di-spirocyclic ones,a new rare 14,15-dinor derivative(9),and three new ones incorporating a y-lactone unit(10-12).An in vitro neuroprotective assay in RSC96 cells revealed that compounds 7 and 12 exhibited neuroprotective activity in a concentration-dependent way,comparable to the reference drug N-acetylcysteine.

Labdane Diterpenoids from Coleus forskohlii （Willd.） Briq.

in order to investigate the active substances of Coleus forskohlii（Wiiid.） Brlq., a new labdane dlterpenold, 12- hydroxy-8,13E-labdadlen-15.olc acid, together with two 8,13-epoxylabd-14-ene-11-one dlterpenolds, 6-acetyl-1- deoxyforskolln and 6-acetyl-1,9-dldeoxyforskolln, was Isolated on the basis of various chromatographic technlques and spectroscopic methods.

Scapaundulin C,a novel labdane diterpenoid isolated from Chinese liverwort Scapania undulate,inhibits acetylcholinesterase activity

In the present study, scapaundulin C(1), a new labdane diterpenoid, and four related known compounds scapaundulin A(2), 5?, 8?, 9?-trihydroxy-13E-labden-12-one(3), 5?, 8?-dihydroxy-13E-labden-12-one(4), and(13S)-15-hydroxylabd-8(17)-en-19-oic acid(5), were isolated from the Chinese liverwort Scapania undulate(L.) Dum., using column chromatography. The structures of these compounds were determined on the basis of 1D- and 2D-NMR analyses. The acetylcholinesterase(Ach E) inhibitory activity was evaluated using a bioautographic TLC assay and the cytotoxic activity was evaluated by the MTT method. All the compounds were reported for the first time to exhibit moderate Ach E inhibitory activity with minimal inhibitory quantities ranging from 250 to 500 ng. All the compounds were tested for their cytotoxicity against five human tumor cell lines, A549, K562, A2780, Hela, and HT29, and compounds 3 and 4 exhibited moderate inhibitory effects on the growth of A2780 cells.

Chemical components of Dysoxylum densiflorum

Three new diterpenoids,including two halimanes,5(10),13E-halimadiene-3α,15-diol(1),and 5(10),14-halimadiene-3α,13ξ-diol(2),one labdane,12-(3-methyl-furan)-labd-8(17)-en-19-oic acid(3),together with sixteen known compounds were isolated from the barks of Dysoxylum densiflorum.All compounds were elucidated by extensive spectroscopic analysis.

New Octadecanoyl Diterpenoid Arabinoside from Conyza blinii

A new octadecanoyl diterpenoid glycoside,（E）-8α,15-dihydroxy-15-（3S-hydroxy-octadecanoyl）-13-labdene-8-O-α-L-arabinopyranoside（1）,was isolated from the aerial parts of Conyza blinii,and the structure was identified on the basis of a detailed spectroscopic analysis,including 2D NMR spectrometry and HRESI-MS.

New diterpenoids isolated from Leonurus japonicus and their acetylcholinesterase inhibitory activity

Three new labdane diterpenoids, leojaponicone A(1), isoleojaponicone A(2) and methylisoleojaponicone A(3), were isolated from the herb of Leonurus japonicus. The chemical structures of these secondary metabolites were elucidated on the basis of 1 D and 2 D NMR, including HMQC, and HMBC spectroscopic techniques. All the new compounds were tested in vitro for their acetylcholinesterase and α-glucosidase inhibitory activity. Compounds 1-3 exhibited low inhibitory effects on α-glucosidase with respect to acarbose and exhibited high inhibitory effects on acetylcholinesterase with respect to huperzine A.

Diterpenoids from the aerial parts of Leonurus macranthus

Four new diterpenoids including one cis clerodane-type(1) and three highly oxygenated labdane-type diterpenes(2–4) were isolated from the aerial parts of Leonurus macranthus. Their structures were elucidated on the basis of spectroscopic data(NMR, UV, IR, and MS). Compound 1 represents the first example of cis clerodane-type diterpene in the plants of Leonurus genus. Compounds 1 and 4 exhibited weak inhibition of nitric oxide production in lipopolysaccharide-stimulated BV-2 microglial cells with IC_(50) values of 35.8 ± 3.6 mmol/L and 48.6 ± 4.8 mmol/L,

Cathayanalactone G and other constituents from leaves and twigs of Callicarpa cathayana

Objective:To study the chemical constituents from the leaves and twigs of Callicarpa cathayana.Methods:The chemical constituents were isolated and purified by column chromatography on silica gel,MCI gel CHP 20 P/P120,Sephadex LH-20,and HPLC.The structures of the compounds were determined by HR-ESI-MS,1 D and 2 D NMR data.Results:A total of 24 compounds were isolated from the 85%methanol extract of leaves and twigs of C.cathayana.They were identified as cathayanalactone G(1),a new diterpene,and 23 known compounds as patagonic acid(2),(-)-16-hydroxycledroda-3,13-dien-16,15-olide-18-oic acid(3),15-methoxypatagonic acid(4),oleanolic acid(5),ursolic acid(6),siaresinolic acid(7),pomolic acid(8),a-amyrin(9),tormentic acid(10),lupeol(11),5,7-dihydroxy-3,4’-dimethoxyflavone(12),5,4’-dihydroxy-3,7,3’-dimethoxyflavone(13),5-hydroxy-3,6,7,4’-tetramethoxyflavone(14),salvigenin(15),kaemferol(16),astragalin(17),pinoresinol 4-O-β-D-glucopyranoside(18),paulownin(19),β-sitosterol(20),β-sitosterolβ-Dglucopyranoside(21),5-hydroxy-coumarin(22),isocopoletin(23),and 4-hydroxycinnamic acid(24).Conclusion:Compound 1 is a new labdane diterpene.Compounds 10,13,16 and 17 are isolated from the genus Callicarpa for the first time.Compounds 7,8,9,12,14,23 and 24 are reported from C.cathayana for the first time.

Antihyperglycemic effect of Juniperus phoenicea L.on alloxan-induced diabetic rats and diterpenoids isolated from the fruits

Objective:To explore the traditional use of Juniperus phoenicea L.(J.phoenicea)growing in Egypt as antidiabetic herb.Methods:The antihyperglycemic activities of the crude 80%ethanol and successive extracts of leaves and fruits of the plant were investigated in alloxan-induced diabetic rats after collecting blood samples through retro-orbital puncture technique.As a consequence of the biological results,phytochemical investigation of the chloroform fraction of fruits was carried out by column chromatography and thin layer chromatography.Results:Results revealed the reduction in blood glucose levels in rats,which were significantly different from control at 4 and 8 weeks(P<0.01).The highest antihyperglycemic activity was exhibited by the crude extracts of fruits and leaves of which the potency was 83.6%and 81.9%,respectively,after 8 weeks,comparing to metformin drug(100%potency).Chloroform fractions of leaves and fruits were the most potent fractions(potencies were 70.3%,71.4%),respectively,along with ethyl acetate fraction of fruits(71.4%).Phytochemical investigating of the chloroform fraction of fruits resulted in the isolation and identification of 5 abietane diterpenoids.Ferruginol,7-dehydroabietanone,sugiol,6-α-hydroxy-7-oxoferruginol,totarolone and a labdane diterpenoid,varodiol were isolated for the first time from the fruits of J.phoenicea growing in Egypt.The identification of these compounds was based on spectroscopic analysis:1hydrogen-nuclear magnetic resonance and electron impact mass spectrometry,comparing the results with the literature.Conclusions:It has become clear that leaves and fruits of the Egyptian J.phoenicea provide effective antihyperglycemic action in diabetic rats as was reported in folk medicine.The high contents of terpenoids in the non-polar fractions may attribute to the antidiabetic effect of the plant.