Chemical Components of Helicia nilagirica Beed.I.Structure of Three New Flavonol Glycosides

Three new flavonol glycosides were isolated from the leaves of Helicia nilagirica Beed.. The structures were elucidated as kaempferol-3-O-b-D-xylopyranosyl-(16)-b-D-glyco- pyranosyl-(12)-a-L-rhamnopyranoside, quercetin-3-O-b-D-xylopyranosyl-(16)-b-D-glycopy- ranosyl-(12)-[-b-D-xylopyranosyl-(14)]-a-L-rhamnopyranoside, and quercetin-3-O-b-D- xylopyranosyl-(16)-b-D-glycopyranosyl-(12)-a-L-rhamnopyranoside, named as Helicianeoside A、B and C, respectively.

Two New Flavonol Glycosides from Bridelia tomentosa

Two new flavonol glycosides, tamarixetin 3-O-β-D-xylopyranosyl-（1-2）-α-L-ribopyranoside （1） and tamarixetin 3-O-α-L-ribopyranoside （2） were isolated from the leaves of Bridelia tomentosa. Their structures were elucidated by 1D and 2D NMR analysis, as well as MS and IR spectra.

New Acetylated Flavonol Glycosides from Knoxia corymbosa

Two new diacetylated flavonol glycosides, kampferol-3-O--3? 6?diacetylglucopyrano- side and quercetin-3-O--3? 6?diacetylglucopyranoside were isolated from knoxia corymbosa. Their structures were elucidated by spectroscopic evidents.

Two New Flavonol Glycosides from Knoxia corymbosa

Two new flavonol glycosides (1 and 2) together with two known flavonoides (3 and 4), were isolated from the whole plant of Knoxia corymbosa willd. The structures of 1 and 2 were elucidated as kaempferol-7-O-α-L-arabinosyl-3-O-β-D-6'-acetylglucopyranoside and kaempferol -7-O-α-L-arabinosyl-3-O-β-D-3',6'-diacetylglucopyranoside respectively.

Forced Degradation of Flavonol Glycosides Extraced from Ginkgo biloba

The degradation of flavonol glycosides extracted from Ginkgo biloba was performed under different conditions and the degraded products were determined by reversed-phase high performance liquid chromatography （RP-HPLC） method.Four stress conditions including acid（0.1 mol/L HCl）,base（0.1 mol/L NaOH）,temperature （70 ℃） and oxidation（0.03% H2O2,volume fraction） were used for the forced degradation studies.The pH stabilities of the flavonol glycosides were determined in phosphate buffers of varying pH values from 4.5 to 7.4.The degradation rate constants and half-life of three Ginkgo flavonol aglycones（quercetin,kaempferol and isorhamnetin） which represent Ginkgo flavonol glycosides were calculated in forced degradation and pH-stability studies of them.The resuits indicate that the three substances were more stable when incubated under acid condition and showed pH-dependent stability.The degradation was observed to follow first-order kinetics in all degradation studies.The stability results could provide important bases on development,preparation and storage of products of Ginkgo biloba extract and should be significantly considered during the further formulation development.

A New Antimicrobial Flavonol Glycoside from Alchornea davidii

A new flavonol glycoside, isorhamnetin-3-O-b-D-xyloside, was isolated from the extract of leaves and twigs of Alchornea davidii (Euphorbiaceae). Its structure was established on the basis of the spectral analysis and chemical degradation. Antimicrobial assay showed that it moderately inhibited the growth of test bacteria (Staphylococcus aureus, Bacillus subtilis and Pseudomonas fluorescens) and fungi (Candida albicans, Aspergillus niger and Trichophyton rubrum) with MICs at 50 g/mL.

A new flavonol glycoside from glandless cotton seeds

A new flavonol glycoside,namely quercetin 3-O-[a-D-apiofuranosyl(1–5)-b-D-apiofuranosyl(1–2)]-a-L-rhamnopyranosyl(1–6)-b-D-glucopyranoside(1),was isolated from glandless cotton seeds together with the known compounds quercetin 3-O-a-L-rhamnopyranosyl(1–2)-[a-Lrhamnopyranosyl(1–6)]-b-D-glucopyranoside(manghaslin,2),kaempferol 3-O-b-D-apiofruranosyl(1–2)-b-D-glucopyranoside(3)and kaempferol 3-O-a-L-rhamnopyranosyl(1–6)-b-D-glucopyranoside(4).It is interesting that the tetrasaccharide fragment of 1 contained both a b-apiosyl and an unusual a-apiosyl group.

Flavonol Glycoside from Psorospermum androsaemifofium

A new flavonol glycoside, 3＇-（4＇＂-（3＇＂＇,4＇＂＇-dihydroxyphenoxy）-2＇＂-hydroxyphenoxy）acanthophorin B （la） to- gether with 3＇-（2＇＂,4＂＇-dihydroxyphenoxy）acanthophorin B （1）, acanthophorin B （2）, vismiaquinone （3）, rheochrysidin （3a）, lupeol acetate and fatty acid were isolated from the chloroform extract of the stem bark of Psorospermum androsaemifolium Baker （Clusiaceae）. The structure of la was determined on the basis of detailed spectroscopic analysis and comparison with the literature. Compounds la and 3a showed moderate antimicrobial activity.

A Simple High-Performance Liquid Chromatography Method for the Assay of Flavonoids in Ginkgo biloba Leaves

Objective:Ginkgo biloba leaves,as an herbal medicine or dietary supplement,have been widely used worldwide.In this study,an integrated analytical method was established for the comprehensive analysis of flavonoids in G.biloba leaves.Materials and Methods:A practical chromatographic method combining high-performance liquid chromatography fingerprint analysis and quantitation was used to simultaneously determine 11 flavonoids(6 flavonol glycosides and 5 biflavones)in G.biloba leaves from different regions.Results:A total of 11 characteristic peaks were identified accurately,and the similarity of fingerprints ranged from 0.944 to 0.996.Methodology validation revealed appropriate linearity(R^(2)≥0.9997),precision,repeatability,stability,and recovery.The total contents of the six flavonol glycosides and five biflavones were within the range of 2.142-8.378 mg/g and 3.759-5.675 mg/g in 19 batches of samples,respectively.Among them,two coumaroyl flavonol glycosides were the predominant components.Conclusions:In this study,a convenient and reliable approach was successfully employed for the comprehensive evaluation of flavonoids in G.biloba leaves,which also provided a reference for its quality standard.

Chemical constituents from Kalanchoe hybrida and their cytotoxicity

Objective：Kalanchoe hybrida（Crassulaceae）is naturalized throughout all the island of Taiwan in China.The preliminary bioassay-guided fractionation of the crude extract of K.hybrida exhibited that the chloroform and n-butanol fractions possessed potent cytotoxicity against MCF-7,NCI-H460,and SF-268 tumor cell lines at 50μg/m L concentration.Therefore,K.hybrida was selected as a target and the chemical constituents from the chloroform and n-butanol fractions of the crude extracts of K.hybrida were identified.The potential constituents were examined for their cytotoxicity against the tumor cell lines.Methods：A combination of conventional chromatographic techniques was performed on the crude extract of K.hybrida.The chemical structures of the purified constituents were identified on the basis of spectroscopic and spectrometric analysis.Results：The purification results had led to the characterization of totally 37 compounds.The isolated compounds 1,2,and 4–12 were examined for their cytotoxicity in vitro,and bufadienolides 4–8 and flavonol glycoside 11 displayed significant cytotoxicity towards all the tested tumor cell lines among these tested compounds.Conclusion：The results indicated that these principles should be responsible for the bioactivity of corresponding partial fractions.The potential constituents could be further investigated to explore the new natural lead drugs.