Studies On Bioactive Constituents From Clematis Tangutica

Clematis tangutica Maxim. Korsh (Ranunculaceae) is distributed in the west ofChina. The whole plants have been used in traditional Tibetan medicine for the treatmentof indigestion and invigorating blood circulation. The plant was the main ingredient of YiXin Kang Tai capsules, a compound preparation of Chinese herbs which has showedsignificant effect of preventing and treating cardiac disease in clinical practice. However,few studies have been reported on chemical constituents of this plant.The systematic chemical constituents of C.tangutica from Tibetan autonomousprefecture of Huangnan in Qing hai province using the normal-phase silica gel, SephadexLH-20, and HPLC to obtain31compounds. Their structures were determined by extensivespectral analysis, physico-chemical constants and chemical evidences. They are6flavonoid glycosides: apigenin-7-O-β-D-(-6’’-p-coumaroyl)-glucopyranoside (1), quercetin-3-O-β-D-galactopyranosyl-7-O-β-D-glucopyranoside (2), isoorientin (3), quercetin-3-O-β-D-galactopyranoside (4), luteolin-7-O-β-D-glucopyranoside (5) and apigetrin (6);24triterpenoid saponins: hederacholichiside F (7),3-O-{-β-D-xylopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→4)]-α-L-arabinopyranosyl}-hederagenin-28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (8), hederagenin-28-O-α-L-rhamno pyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (9),3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl3β,21α,23-trihydroxyolean-12-en-28-oic acid-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (10), leontoside(11),3-O-β-D-galactopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl-hederagenin-28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (12), hederagenin-28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (13), kizutasaponin K12(15), clematibetoside C (16), cauloside D (17), saponin PJ3(18),hederacholichiside E (19),3-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl-3β,23-dihydroxyolean-18-en-28-oic acid-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (20),3-O-β-D-xylopyranosyl-(1→2)-α-L-arabinopyranosyl-hederagenin-28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (21), cussonoside A (22), ciwujianoside C3(23),3-O-β-D-ribopyranosyl-olean olicacid-28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside(24), asperosaponin VI (25),3-O-α-L-arabinopyranosyl-gypsogenin-28-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (26), oleanolic acid-28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (27), cussonoside B (28), hederagenin-28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside (29), HN-saponin F (30) and CP1(31);1esters: dibutyl phthalate (14). Compounds8–10,13,20,21and24are newcompounds, compounds1,7,11,12,19,23and25–30are obtained from the genusClematis for the first time, while all compounds are isloated for the first time from thespecies of Clematis except15and18.Saponins7,911,13,1517,20and25were evaluated for their protective effects inhypoxia-induced myocardial injury model, diltiazem as the positive control. The resultindicated that saponins9,10,13,17and25exhibited moderate protective effects againstLDH and CK MB release; the ED50values were77.31,114.26,92.44,127.22,120.33and75.77,110.51,87.39,121.92,109.48M, respectively. Compounds7,11,15,16and20showed no cardioprotective activities. Compound1was evaluated for its anti-ischemic brain injury activity in middlecerebral artery occlusion (MCAO) model for the first time. The result indicated thatcompound1at25,50and100mg/kg group significantly reduced infarct volume anddecreased neurological deficit scores compared with MCAO group alone, and it wasshowed dose dependent.Innovations and significance:1. The systematic chemical constituents of C.tangutica was investigated,31compounds were isolated and identified. Twelve compounds are first reported from thespecies and seven are novel compounds.2. The aglycone of the new triterpenoid saponin10isolated from C.tangutica waselucidated as3β,21α,23-trihydroxyolean-12-en-28-oic acid, which is reported in nature forthe first time.3β,23-dihydroxyolean-18-en-28-oic acid, the aglycone of compound20, wasrelatively rare in nature. And3-O-disaccharide chain “Xyl(1→2)Ara-” of compound21has not been reported in oleanane-type triterpene saponins. The structures of the saponinswere significant different from the saponins isolated from the other plants of the genusClematis. This might be associated with the special cold and anoxic environment in whichC.tangutica growing inhabits. On the other hand, these results also have importantsignificance for the chemotaxonomy of the Clematis species.3. Anti-myocardial ischemia activity of triterpenoid saponins was elucidated in vitro.Five compounds showed moderate cardioprotective activities and the preliminarystructure-activity relationship was also discussed.4. Compound1can be used for preparing drugs for treating ischemic brain injury.The research results have provided a reasonable base for its further exploitation andvaluable leads for pursuing new drugs which can treat stroke.5. The above research results might help to clarify the basis of efficacy of the “Yi XinKang Tai capsule” which is mainly composed of C.tangutica. As well as they providedscientific basis for revising the quality standards of preparation and medicinal materials, further development of cardiovascular drugs.