Flavonoid glycosides from the leaves of Michelia champaca.

Michelia champaca L. (Magnoliaceae) was cultivated in large scale for flowers as cosmetic raw materials, whereas the value of its leaves remains to be discovered. Our chemical study on the leaves yielded four new flavonol diglycosides, champaflavosides A-D (1-4), together with twenty-three known flavonoid glycosides (5-27). Their structures were determined by spectroscopic and chemical methods. Compounds 5-21 and 23-27 were not previously reported from the genus Michelia, and kaempferol 3-O-rutinoside (22) was obtained from this species for the first time. All the compounds were evaluated for antioxidant activity by four in vitro assays. Compounds 3-12 and 20 showed more potent 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity than l-ascorbic acid (l-AA). Compounds 2-23, 25, and 27 exhibited 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity superior to l-AA. The ferric reducing antioxidant powers (FRAP) of compounds 2-13, 17, and 19 were higher than l-AA. Further, eighteen compounds demonstrated cellular reactive oxygen species (ROS) scavenging activity, of which champaflavoside D (4), rhamnetin 3-O-neohesperidoside (8), quercetin 3-O-(6-O-E-p-coumaroyl)-neohesperidoside (9), and liquiritin (27) were more potent than curcumin. The results revealed that the renewable leaves of M. champaca are a rich source of flavonoids and antioxidants.

Dihydrochalcone C-glycosides from Averrhoa carambola leaves.

Ten undescribed dihydrochalcone C-glycosides, carambolasides R1‒R3, S1, S2, T1‒T3, 3-hydroxycarambolaside T1, and 3-hydroxycarambolaside P were isolated along with carambolasides I and P from the leaves of Averrhoa carambola L. (Oxalidaceae). Their structures were determined by spectroscopic and chemical methods. Among them, carambolasides P, T1, T2, and I with contents of 22.78, 14.39, 4.93, and 1.87 mg g-1 dry wt., respectively, were shown to be abundant in the leaves by HPLC analysis. All the compounds showed more potent ABTS radical cation scavenging activity than l-ascorbic acid. 3-Hydroxycarambolaside T1 and 3-hydroxycarambolaside P also demonstrated moderate DPPH radical scavenging activity. Further, carambolaside R3, 3-hydroxycarambolaside T1, and 3-hydroxycarambolaside P exhibited weak in vitro porcine pancreatic lipase inhibitory activity.

Flavan-3-ols and 2-diglycosyloxybenzoates from the leaves of Averrhoa carambola.

Averrhoa carambola L. (Oxalidaceae) was widely cultivated for fruits (star fruit), whereas the value of leaves remains to be discovered. Our study on the leaves yielded five flavan-3-ols (1-5) and two 2-diglycosyloxybenzoates. Their structures were determined by spectroscopic and chemical methods. Epicatechin-(5,6-bc)-4ß-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (1) and benzyl 2-ß-d-apiofuranosyl-(1 â†’ 6)-ß-d-glucopyranosyloxybenzoate (6) were new structures. 6-(S-2-Pyrrolidinone-5-yl)epicatechin (4) and 6-(R-2-pyrrolidinone-5-yl)epicatechin (5) were obtained as monomeric diastereomer for the first time and their absolute configurations were determined by electronic circular dichroism (ECD) computation. Epicatechin-(7,8-bc)-4α-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (2), epicatechin-(7,8-bc)-4ß-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (3), and methyl 2-ß-d-apiofuranosyl-(1 â†’ 6)-ß-d-glucopyranosyloxybenzoate (7) were not previously reported from the genus Averrhoa. Compounds 1-5 showed more potent 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities and ferric reducing antioxidant power (FRAP) than l-ascorbic acid. Meanwhile 1 and 3 exhibited lipase and α-glucosidase inhibitory activities, respectively. The results clarified the structures of flavan-3-ols and 2-diglycosyloxybenzoates in the leaves and their antioxidant, lipase, and α-glucosidase inhibitory activities.

Carotenoid-Derived Flavor Precursors from Averrhoa carambola Fresh Fruit.

The fruit of Averrhoa carambola L. (Oxalidaceae), commonly known as star fruit or carambola, is popular in tropical and subtropical regions. Carotenoid-derived components, mainly C13- and C15-norisoprenoids, contribute greatly to the flavor of star fruit. Previously reported norisoprenoids were tentatively identified by GC-MS analysis after enzymatic hydrolysis. To gain accurate information about glycosidically bound flavor precursors in star fruit, a phytochemical study was conducted, which led to the isolation of 16 carotenoid derivatives-One new C13-norisoprenoid glucoside, (5R,6S,7E,9R)-5,6,9-trihydroxy-7-megastigmene 9-O-ß-d-glucoside (1); one new C15-norisoprenoid, (6S,7E,10S)-Δ9,15-10-hydroxyabscisic alcohol (11); and 14 known ones, of which 12 were in glucoside form. The structures of the two new compounds were elucidated on the basis of extensive spectroscopic data analysis and chemical reaction. Compound 11 was a rare C15-norisoprenoid with a double bond between C-9 and C-15, and its possible biogenetic pathway was proposed. The known compounds were identified by comparison of their mass and nuclear magnetic resonance (NMR) data with those reported in the literature. The structure identification of one new (1) and seven known (3⁻7, 9, and 10) C13-norisoprenoid glucosides from the genus Averrhoa for the first time enriches the knowledge of carotenoid-derived flavor precursors in star fruit.

Hydroquinone and terpene glucosides from Leontopodium leontopodioides and their lipase inhibitory activity.

Three new glucosides of hydroquinone, monoterpene, and megastigmane, benzyl 2,5-dihydroxybenzoate 5-O-ß-d-glucopyranoside (isotrichocarpin, 1), (2S,3R)-3,7-dimethyl-6-octene-1,2,3-triol 2-O-ß-d-glucopyranoside (leontopodioside D, 4), and (6R,7R,8R,9S)-6,9-epoxy-7,8-dihydroxymegastigman-4-en-3-one 8-O-ß-d-glucopyranoside (leontopodioside E, 7) were isolated from the whole herbs of Leontopodium leontopodioides (Willd.) Beauv. (Asteraceae), along with nebrodenside A (2), pungenin (3), betulalbuside A (5), geranyl O-ß-d-glucopyranoside (6), and 3ß-hydroxy-ß-ionone 3-O-ß-d-glucopyranoside (8). Their structure were determined by spectroscopic and chemical methods. All the known compounds were reported from this species for the first time. Compounds 2-6 showed potent in vitro pancreatic lipase inhibitory activity, suggesting their participation in the reductive effect of the herbs on triglyceride absorption.

Phenolics from strawberry cv. Falandi and their antioxidant and α-glucosidase inhibitory activities.

Three new phenolic glucosides, falandiosides A (1), B (2), and C (6) were isolated from strawberry (Fragaria×ananassa Duch.) cv. Falandi fruit, together with three flavone glucuronides (3-5), eleven lignan glycosides (12-22), and five others. Their structures were determined by spectroscopic methods. All the known phenolics were reported from strawberry for the first time. They were evaluated for antioxidant and α-glucosidase inhibitory activities. Three new and fifteen known phenolics showed potent 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity with IC50 values of 22.50-4.28µM in comparison to l-ascorbic acid (14.21µM). Quercetin 3-(6-methylglucuronide) (4), (+)-isolariciresinol 9'-glucoside (12), and (-)-isolariciresinol 9'-glucoside (13) were active in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Moreover, compounds 12 and 13 had moderate ferric reducing antioxidant power (FRAP) values. Further, two new and seven known phenolics exhibited more potent α-glucosidase inhibitory activity with IC50 values of 537.43-25.39µM than acarbose (619.94µM).

Anti-inflammatory cyclopeptides from exocarps of sugar-apples.

Two new cyclic peptides, fanlizhicyclopeptide A, cyclo(Pro(1)-Pro(2)-Tyr(3)-Leu(4)-Pro(5)-Gly(6)-Val(7)) (1), and fanlizhicyclopeptide B, cyclo(Pro(1)-Ile(2)-Tyr(3)-Ala(4)-Gly(5)) (2), were isolated along with six known kaurane diterpenoids and a known clovane sesquiterpene from the exocarps of sugar-apples, the fruit of Annona squamosa. Their structures were elucidated by ESI MS/MS experiments, 1D and 2D NMR data and chemical degradation. In the anti-inflammatory assay, both 1 and 2 showed in vitro inhibitory effects on the production of pro-inflammatory cytokines, TNF-α and IL-6, in LPS-stimulated RAW 264.7 macrophages.

Flavonoids from the pericarps of Litchi chinensis.

A new methylene-linked flavan-3-ol dimer, bis(8-epicatechinyl)methane (1), was isolated from the pericarps of Litchi chinensis Sonn. (Sapindaceae), together with dehydrodiepicatechin A (2), proanthocyanidin A1 (3), proanthocyanidin A2 (4), (-)-epicatechin (5), 8-(2-pyrrolidinone-5-yl)-(-)-epicatechin (6), (-)-epicatechin 8-C-ß-D-glucopyranoside (7), naringenin 7-O-(2,6-di-O-α-L-rhamnopyranosyl)-ß-D-glucopyranoside (8), and rutin (9). It was the first report of compound 2 as a natural product and compounds 6-8 from this species. Compounds 1, 2, and 6-8 were evaluated for antioxidant activity. The ferric reducing antioxidant powers (FRAP) of compounds 1 and 6 were comparable to that of L-ascorbic acid, and the scavenging activities of compounds 1, 2, 6, and 7 toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) radical cations were more potent than those of L-ascorbic acid; compound 8 was weak in FRAP and DPPH assays.

Phenolics from Ageratina adenophora roots and their phytotoxic effects on Arabidopsis thaliana seed germination and seedling growth.

A bioassay-directed phytochemical study was conducted to investigate potential allelochemicals in the roots of the invasive plant Ageratina adenophora. Eleven phenolic compounds, including seven new ones, 7-hydroxy-8,9-dehydrothymol 9-O-trans-ferulate (1), 7-hydroxythymol 9-O-trans-ferulate (2), 7,8-dihydroxythymol 9-O-trans-ferulate (3), 7,8-dihydroxythymol 9-O-cis-ferulate (4), methyl (7R)-3-deoxy-4,5-epoxy-D-manno-2-octulosonate 8-O-trans-p-coumarate (5), methyl (7R)-3-deoxy-4,5-epoxy-D-manno-2-octulosonate 8-O-cis-p-coumarate (6), and 3-(2-hydroxyphenyl)propyl methyl malonate (7), were isolated from a bioactive subfraction of the ethanol extract of the roots of A. adenophora. The new structures were established on the basis of detailed spectroscopic analysis. The potential phytotoxic effects of these compounds on the germination of Arabidopsis thaliana seeds were tested by a filter paper assay. Compound 7 and known compounds 3-(2-hydroxyphenyl)-1-propanol (8) and o-coumaric acid (9) remarkably showed inhibition activity against Arabidopsis seed germination at a concentration of 1.0 mM. Compounds 1, 2, 5, 6, and 10 showed slight inhibitory activity at the test concentration after treatment for 3 days, while the other compounds showed no obvious inhibitory effects. Moreover, 7-9 were further found to show obvious inhibitory activity on retarding the seedling growth of Ar. thaliana cultured in soil medium.

Phenolic constituents from the roots of Mikania micrantha and their allelopathic effects.

Four new thymol derivatives, 8,10-dihydroxy-9-benzoyloxythymol (1), 9-isobutyryloxy-10-hydroxythymol (2), 7,8,9,10-tetrahydroxythymol (3), and 7,8,10-trihydroxy-9-E-feruloyloxythymol (4), were isolated from the fresh roots of Mikania micrantha , along with 8,9,10-trihydroxythymol (5), 8,10-dihydroxy-9-acetoxythymol (6), 8,10-dihydroxy-9-isobutyryloxythymol (7), 8,10-dihydroxy-9-(2-methylbutyryloxy)thymol (8), 8,9-dehydro-10-hydroxythymol (9), 8-methoxy-9-hydroxythymol (10), ethyl caffeate (11), ethyl ferulate (12), 3,5-di-O-caffeoylquinic acid (13), and mikanin (14). Their structures were determined by spectroscopic methods. The known thymol derivatives (5-10) were obtained from the genus Mikania for the first time. Allelopathic effects of these compounds on Arabidopsis thaliana seeds were evaluated by a filter paper assay. After the treatment at 0.1 mM for 4 days, the seed germination rate with compound 8 was 48% and the inhibitory rates of shoot growth with compounds 1, 2, 7-10, and 12 were over 40%. The IC50 values of compounds 1 and 8 on shoot growth were 342.5 and 625 µM, respectively.

Further acylated flavonol bisdesmosides from Sinocrassula indica.

Further investigation on the whole herbs of Sinocrassula indica (Crassulaceae) led to the isolation of four new acylated flavonol bisdesmosides, sinocrassosides A13, B6, B7, and D4, together with kaempferol 3-O-ß-D-(6-O-acetyl)glucopyranosyl-7-O-α-L-rhamnopyranoside. Their structures were established by spectral and chemical methods.

Flavonoids from the capitula of Eriocaulon australe.

A flavan, eriocaulin A (1), and three flavone acyl glucosides, eriocaulosides A-C (2-4) were isolated from the capitula of Eriocaulon australe R. Br. (Eriocaulaceae), a Chinese medicine and an herb for health care beverages, together with seven known flavones and three isoflavones (5-14). The new flavonoids were elucidated as (2S)-3',4'-methylenedioxy-5-methoxy-7-hydroxyflavan (1), hispidulin 7-O-ß-D-(6-O-cinnamoyl)glucopyranoside (2), jaceosidin 7-O-ß-D-(6-O-p-coumaroyl)glucopyranoside (3), jaceosidin 7-O-ß-D-(6-O-p-hydroxybenzoyl)glucopyranoside (4) based on their spectroscopic data. All the 14 flavonoids were obtained from this species for the first time. The in vitro cytotoxicity of compounds 1-14 against human lung adenocarcinoma A549, human breast adenocarcinoma MCF-7, and human cervical carcinoma HeLa cell lines was evaluated using the MTT colourimetric assay. Compounds 1, 7, and 9 were cytotoxic to A549, compounds 1, 2, 7, 9, 12, and 14 to MCF-7, and compounds 7, 9, and 14 to HeLa cells, with IC50 values ranging from 7.17 to 29.57 µg/ml, while the others were inactive (IC50>50 µg/ml).

Abietane diterpenoids from Isodon lophanthoides var. graciliflorus and their cytotoxicity.

Seven new (1-7) and three known (8-10) abietane diterpenoids were isolated from the methanolic extract of the aerial parts of Isodon lophanthoides var. graciliflorus (Lamiaceae), a folk Chinese medicine and an herb for functional beverages. They were identified as 16-acetoxylsugiol (1), graciliflorin E (2), graciliflorin F (3), 15-O-methylgraciliflorin F (4), 15-hydroxy-20-deoxocarnosol (5), 3ß-hydroxysempervirol (6), 15-hydroxy-1-oxosalvibretol (7), abieta-8,11,13-triene-14,19-diol (8), 6,12,15-trihydroxy-5,8,11,13-abietatetraen-7-one (9), and 3α-hinokiol (10) based on the spectroscopic data including COSY (correlated spectroscopy), HMBC (heteronuclear multiple bond correlation), and HR-ESI-MS (high-resolution electrospray ionization mass spectrometry). All the compounds except 10 were obtained from I. lophanthoides for the first time. Compounds 1, 2, 5, 6, 8, and 9 exhibited in vitro cytotoxicity against A549 (human lung adenocarcinoma), MCF-7 (human breast adenocarcinoma), and HeLa (human cervical carcinoma) cell lines with the IC(50) values of 1.79-52.67 µM.

Podocarpane, isopimarane, and abietane diterpenoids from Isodon lophanthoides var. graciliflorus.

Four new diterpenoids including two podocarpanes, graciliflorins A (1) and B (2), an isopimarane acetal, graciliflorin C (3), and a rearranged abietane, graciliflorin D (4) were isolated from the aerial parts of Isodon lophanthoides var. graciliflorus (Lamiaceae) along with podocarpa-8,11,13-triene-3α,13-diol (5) and micranthin B (6). Their structures were elucidated based on the spectroscopic data. The in vitro cytotoxicity of compounds 1-4 and 6 against human carcinoma A549, MCF-7, and HeLa cell lines were evaluated using the MTT colourimetric assay. Micranthin B (6) showed moderate activity against all the cells with IC(50) values of 16.29, 18.20, and 22.25 µM, while compounds 1-4 were inactive (IC(50)>50 µg/ml).

Grasshopper ketone 3-O-primveroside from Sinocrassula indica.

A new megastigmane glycoside, grasshopper ketone 3-O-primveroside (1), was isolated from the methanolic extract of the whole herbs of Sinocrassula indica (Crassulaceae). Its structure was elucidated on the basis of spectral and chemical evidence.

Flavonoid Glycosides from the Seeds of Litchi chinensis.

Seven flavonoid glycosides, including one new (1) and five previously uncharacterized (3-7), were obtained from the seeds of lychee ( Litchi chinensis Sonn. cv. Heiye) by means of repetitive column chromatography and high-performance liquid chromatography (HPLC) preparation. They were identified as litchioside D (1), (-)-pinocembrin 7-O-neohesperidoside (2), (-)-pinocembrin 7-O-rutinoside (3), taxifolin 4'-O-ß-d-glucopyranoside (4), kaempferol 7-O-neohesperidoside (5), tamarixetin 3-O-rutinoside (6), and phlorizin (7) on the basis of spectroscopic analysis and comparison of their data to the values reported in the literatures. Among them, compounds 1, 4, and 5 showed in vitro antitumor activity against A549, LAC, Hep-G2, and HeLa cell lines in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay.

A novel cyclopropyl-containing fatty acid glucoside from the seeds of Litchi chinensis.

3,12-Dihydroxy-cis-3,4-methylenedodecanoic acid 3-O-ß-d-glucopyranoside, trivially named litchioside C (1), the first cyclopropyl-containing fatty acid glycoside, was isolated along with three previously uncharacterized galactosylacylglycerols from the seeds of Litchi chinensis. Its structure was established on the basis of spectroscopic analysis including HRESIMS and 2D NMR spectra. Its antioxidant and antibacterial activities were evaluated and its biogenetic pathway was discussed.

Monoterpenoid indole alkaloids mediating DNA strand scission from Turpinia arguta.

Two new monoterpenoid indole alkaloid derivatives, turpiniside (1) and 11-methoxyjavaniside (2), along with the known alkaloids, vincosamide (3), (3 R)-pumiloside (4), and paratunamide C (5), were isolated from the leaves of Turpinia arguta (Lindl.) Seem. Their structures were determined on the basis of spectroscopic data. Compounds 1 and 3-5 were found to effect relaxation of the supercoiled pBR322 plasmid DNA in the presence of Cu²+.

A-type proanthocyanidins from lychee seeds and their antioxidant and antiviral activities.

Two new A-type trimeric proanthocyanidins with two doubly bonded interflavanoid linkages, litchitannin A1 [epicatechin-(2ß→O→7,4ß→6)-epicatechin-(2ß→O→7,4ß→8)-catechin] (1) and litchitannin A2 [epicatechin-(2ß→O→7,4ß→6)-epicatechin-(2ß→O→7,4ß→6)-epicatechin] (2), were isolated from lychee (Litchi chinensis Sonn. cv. Heiye) seeds together with aesculitannin A (3), epicatechin-(2ß→O→7,4ß→8)-epiafzelechin-(4α→8)-epicatechin (4), proanthocyanidin A1 (5), proanthocyanidin A2 (6), proanthocyanidin A6 (7), epicatechin-(7,8-bc)-4ß-(4-hydroxyphenyl)-dihydro-2(3H)-pyranone (8), and epicatechin (9). Their structures were elucidated on the basis of spectroscopic and chemical evidence. It is the first time that compounds 1-4, 7, and 8 have been reported in this species. Compounds 1-9 showed more potent antioxidant activity than L-ascorbic acid with ferric reducing antioxidant power (FRAP) values of 3.71-24.18 mmol/g and IC50 values of 5.25-20.07 µM toward DPPH radicals. Moreover, litchitannin A2 (2) was found to exhibit in vitro antiviral activity against coxsackie virus B3 (CVB3) and compounds 3 and 6 displayed antiherpes simplex virus 1 (HSV-1) activity.

The first cyclic phenolic acid glycoside dimer and new alpha-tetralone and triterpenoid glucosides from Gentiana loureirii.

Further chemical investigation of the whole plants of Gentiana loureirii led to the isolation and characterization of three new compounds, cyclic 4-O-beta-D-glucopyranosylcaffeic acid dimer (1), a new alpha-tetralone, 4-hydroxy-6-methyl-alpha-tetralone 4-O-beta-D-glucopyranoside (2), and 3beta,30-dihydroxy-12-ursen-28-oic acid 28-O-beta-D-glucopyranosyl ester (3), along with five known compounds. To the best of our knowledge, compound 1 is the first cyclic phenolic acid glycoside dimer.