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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)-4β-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (1) and benzyl 2-β-d-apiofuranosyl-(1 → 6)-β-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)-4β-(p-hydroxyphenyl)-dihydro-2(3H)-pyranone (3), and methyl 2-β-d-apiofuranosyl-(1 → 6)-β-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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A novel icariin type flavonoid glycoside with a malonaldehydic acid intramolecular ester and two known flavonoid glycosides were isolated from Epimedium pseudowushanense . Their structures were elucidated on the basis of spectroscopic analysis and comparison of their data to the values reported in the literatures. The anti-inflammatory activities of these compounds icariin 3'''- O -malonaldehydic acid intramolecular 1'''', 2''' ester (1), icariin (2) and epimedin C (3) were tested. The results indicated that compounds 1, 2 and 3 showed maximal inhibitory ratio of 27.91, 44.80 and 46.61%, respectively in in vitro anti-inflammatory activity on LPS-induced TNF-α secretion in RAW264.7 cells. Compounds icariin (2) and epimedin C (3) were found to inhibit the secretion of TNF-α to a comparable degree as quercetin.

Thirteen flavonoids were isolated from the fresh sweet fruit of Averrhoa carambola L. (Oxalidaceae), commonly known as star fruit, and their structures were determined by spectroscopic and chemical methods. 8-Carboxymethyl-(+)-epicatechin methyl ester, pinobanksin 3-O-β-d-glucoside, and carambolasides M-Q were undescribed structures. (+)-Epicatechin, aromadendrin 3-O-β-d-glucoside, helicioside A, taxifolin 3'-O-β-d-glucoside, galangin 3-O-rutinoside, and isorhamnetin 3-O-rutinoside were reported from this species for the first time. Pinobanksin 3-O-β-d-glucoside and carambolasides M-Q showed more potent 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity (IC 50  = 5.3-2.3 μM) than l-ascorbic acid (10.5 μM). Further, (+)-epicatechin, pinobanksin 3-O-β-d-glucoside, isorhamnetin 3-O-rutinoside, and carambolasides O-Q exhibited weak porcine pancreatic lipase inhibitory activity., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

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-β-D-glucopyranoside (7), naringenin 7-O-(2,6-di-O-α-L-rhamnopyranosyl)-β-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.

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-β-D-(6-O-cinnamoyl)glucopyranoside (2), jaceosidin 7-O-β-D-(6-O-p-coumaroyl)glucopyranoside (3), jaceosidin 7-O-β-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)., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

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-β-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.

Four novel prenylflavonols, macaranones A-D (1-4), were isolated from the leaves of Macaranga sampsonii. Their structures were elucidated on the basis of spectroscopic data. Macaranones C (3) and D (4) represent first two examples of flavonols having an unusual peltogynoid skeleton which is formed from a 2'-geranylflavonol by cyclization between 3-OH and C-1'' of the 2'-geranyl substituent of the flavonol. Compounds 1-4 were evaluated for the cytotoxicity against several human cancer cell lines.

Longan fruits contain a significant amount of polyphenols. In the present study, polyphenols were extracted from longan pericarp tissues, and then two representative polyphenols were separated and purified by polyamide column chromatography, Sephadex LH-20 column chromatography, and silica gel column chromatography. On the basis of 1H NMR, 13C NMR, and electrospray ionization mass spectrometric (ESI-MS) data, the two compounds were identified as 4-O-methylgallic acid and (-)-epicatechin, respectively. In terms of reaction with longan polyphenol oxidase (PPO), (-)-epicatechin was further identified as the PPO substrate that caused longan fruit to brown. The results of antioxidant activity showed that 4-O-methylgallic acid had higher reducing power and 2,2-diphenyl-1-picrylhydrazyl- (DPPH-), hydroxyl radical-, and superoxide radical-scavenging activities than (-)-epicatechin.

Abstract: The first stilbene possessing a γ-aminobutyric acid lactam function, artocarpene (1), and a new flavanone, 2-hydroxynaringenin 4′-O-β-d-glucopyranoside (2), were isolated from the stems of Artocarpus nitidus subsp. lingnanensis along with four known compounds, 2-hydroxynaringenin (3), oxyresveratrol (4), 3,4′,5-trihydroxy-3′-prenylstilbene (5) and norartocarpetin (6). Their structures were elucidated on the basis of spectroscopic data. Compounds 1 exhibited weak antioxidant activity and 2 displayed weak cytotoxicity against human lung cancer A549 cell line. [Copyright &y& Elsevier]

Abstract: Eleven flavonoids including a new flavone glycoside, 7,3′-dihydroxy-4′-methoxyflavone-7-O-β-glucopyranoside, and a quinolizidine alkaloid, lupanine, were isolated from the seeds of two Ammopiptanthus (Leguminosae) species, Ammopiptanthus mongolicus and Ammopiptanthus nanus. 7,3′-Dihydroxy-4′-methoxyflavone and lupanine were the major constituents in the seeds of both species. The patterns of seed flavonoids presented a clear systematic relationship between the two species. The simple seed alkaloid composition was presumed to be responsible for the weak defense capability of the seeds to insect pests in both species. [Copyright &y& Elsevier]