植物多酚研究与利用的意义及发展趋势*

植物多酚(植物单宁) 是一类广泛存在于植物体内的重要的天然产物。多年来它们一直用于许多传统工业领域如制革、石油开采和木材胶粘剂的生产。近30 年来, 随着植物多酚化学的发展, 植物多酚的化学结构和性质已被深入揭示。根据美国化学文摘(CA ) 近30 年相关文献资料的统计分析, 阐述了植物多酚化学的发展状况及其作为一类丰富的可再生绿色资源的利用情况, 讨论了植物多酚化学的研究发展趋势和广阔的应用前景。     

Antioxidant potential of polyphenols and tannins from burs of Castanea mollissima Blume

Spiny burs of Castanea mollissima Blume (Chinese chestnut) are usually discarded as industrial waste during post-harvesting processing. The objective of this study was to establish an extraction and isolation procedure for tannins from chestnut burs, and to assess their potential antioxidant activity. Aqueous ethanol solution was used as extraction solvent, and HPD 100 macroporous resin column was applied for isolation. The influence of solvent concentration in the extraction and elution process on extraction yield, tannins and polyphenols content, as well as antioxidant potential, including DPPH and ABTS radical scavenging ability, reducing power ability and cellular antioxidant ability were assessed. In both the extraction and isolation process, 50% aqueous ethanol led to superior total tannins and polyphenols content as well as significantly higher antioxidant activity. In addition, the antioxidant activity and the total tannins content in extracts and fractions had a positive linear correlation, and the predominant components responsible for antioxidant activities were characterized as hydrolysable tannins. To the best of our knowledge, this is the first report on the enrichment of tannins from burs of C. mollissim using macroporous resin chromatography, and to assess the cellular antioxidant activity of them.     

Antioxidant activities and polyphenolic contents of three selected Micromeria species from Croatia

Antioxidant activities of three selected Micromeria species growing in Croatia (M. croatica, M. juliana and M. thymifolia) were evaluated using five different antioxidant assays, in comparison with plant polyphenolic constituents and reference antioxidants. All studied ethanolic extracts exhibited considerable activity to scavenge DPPH and hydroxyl free radicals, reducing power, iron chelating ability and total antioxidant capacity in the order: M. croatica > M. juliana > M. thymifolia. Total polyphenol (9.69-13.66%), phenolic acid (5.26-6.84%), flavonoid (0.01-0.09%) and tannin (3.07-6.48%) contents in dried plant samples were determined spectrophotometrically. A strong positive correlation between antioxidant activities and contents of phenolic acids and tannins was found, indicating their responsibility for effectiveness of tested plants. Our findings established Micromeria species as a rich source of antioxidant polyphenols, especially the endemic M. croatica.     

Phytochemical Investigation and Biological Activities of Lantana rhodesiensis

Lantana rhodesiensis Moldenke is a plant widely used to treat diseases, such as rheumatism, diabetes, and malaria in traditional medicine. To better understand the traditional uses of this plant, a phytochemical study was undertaken, revealing a higher proportion of polyphenols, including flavonoids in L. rhodesiensis leaf extract and moderate proportion in stem and root extracts. The antioxidant activity of the extracts was also determined using three different assays: the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, the FRAP method (Ferric-reducing antioxidant power) and the β-carotene bleaching test. The anti-malarial activity of each extract was also evaluated using asexual erythrocyte stages of Plasmodium falciparum, chloroquine-sensitive strain 3D7. The results showed that the leaf extract exhibited higher antioxidant and anti-malarial activities in comparison with the stem and root extracts, probably due to the presence of higher quantities of polyphenols including flavonoids in the leaves. A positive linear correlation was established between the phenolic compound content (total polyphenols including flavonoids and tannins; and total flavonoids) and the antioxidant activity of all extracts. Furthermore, four flavones were isolated from leaf dichloromethane and ethyl acetate fractions: a new flavone named rhodescine (5,6,3′,5′-tetrahydroxy-7,4′-dimethoxyflavone) (1), 5-hydroxy-6,7,3′,4′,5′-pentamethoxyflavone (2), 5-hydroxy-6,7,3′,4′-tetramethoxyflavone (3), and 5,6,3′-trihydroxy-7,4′-dimethoxyflavone (4). Their structures were elucidated by ¹H, ¹³CNMR, COSY, HSQC, HMBC, and MS-EI spectral methods. Aside from compound 2, all other molecules were described for the first time in this plant species.     

Characterization of oxidized tannins: comparison of depolymerization methods,asymmetric flow field-flow fractionation and small-angle X-ray scattering

Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L⁻¹), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was done at low concentration (0.1 g L⁻¹), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble macromolecules have a weight average molecular weight ten times higher than the soluble ones.     

Advanced separation methods of food anthocyanins,isoflavones and flavanols

In recent years, increasing knowledge of the positive health effects of food polyphenols has prompted the need to develop new separation techniques for their extraction, fractionation and analysis. This article provides an updated and exhaustive review of the application of counter-current chromatography, high performance liquid chromatography, capillary electrophoresis, and their hyphenation with mass spectrometry to the study of food polyphenols. Flavonoids constitute the largest class of polyphenols, widely spread in the plant kingdom and common in human diet which has been the most widely studied with respect to their antioxidant and biological activities. The main subgroups are anthocyanins, catechins, isoflavones, flavonols and flavones. They are reported to exhibit antioxidant, anti-carcinogenic, anti-inflammatory, anti-atherogenic, anti-thrombotic, and immune modulating functions, among others. Since red fruit anthocyanins, soy isoflavones and flavanols from grapes and teas are currently the most used phenolic compounds for producing new nutraceuticals and functional foods, this review is focused on these three flavonoid groups.     

Green extraction process of tannins obtained from Moroccan Acacia mollissima barks by microwave: Modeling and optimization of the process using the response surface methodology RSM

The effect of extraction conditions on polyphenols contents and condensed tannins by microwave-assisted extraction (MAE) was studied for the first time to our knowledge. Moroccan barks of Acacia mollissima was used to extract phenolic compounds. The variables studied are the following: power extraction, time extraction and solvent nature. Five powers extraction were tested: 150 W, 250 W, 300 W, 450 W and 600 W. A significant effect of power extraction on the extractable nature was proved by ANOVA and Student test. The yields were also affected by time extraction. Different solvent (water, ethanol, methanol and ethyl acetate) were tested to evaluate the best extraction solvent according to the extractable nature. Highest polyphenols contents were obtained with methanol. The proportion of this solvent, time extraction and power extraction were optimized using the response surface methodology (RSM). A face-centered composite design (FCCD) was applied to evaluate the effects of these variables on the polyphenols and condensed tannins contents. For each experiment, the extraction yield, the total polyphenolic contents and the condensed tannins contents were quantified using colorimetric essays. The extracts were characterized by their reactivity to formaldehyde and reverse phase high pressure liquid chromatography (RP-HPLC). The highest polyphenols content was obtained at 156 W using 80% of methanol during 5 min. For condensed tannins, the highest content of cyanidin was obtained at 182 W using 20% of methanol during 3.66 min. RSM applied in MAE, permitted to develop green extraction process of polyphenols and tannins extracted, using lower microwave power and methanol proportion with a shortest time extraction and in the same time improve the quantity of extractables obtained from renewable natural resource.     

Anticancer potential of Annona genus: A detailed review

Genus Annona is widely distributed in tropical and subtropical regions around the world. From root to shoot, plant parts of different species of Annona were used traditionally in many countries for treatment of different types of diseases and as a general health supplement. It is naturally enriched with a large number of bioactive molecules which attributed to the several biological activities including antioxidant, anti-inflammatory, antimicrobial and anticancer effects. These bioactive constituents isolated from the leaf, bark, fruit and stem of this plant genus have found terpenoids, steroids, flavonoids, cardiac glycosides, tannins, phenols and alkaloids. Studies have reported that annonaceous acetogenins and alkaloids from this genus were very effective against different types of tumour cell lines. This review highlights anticancer effects of Annona species in cancer therapy, the efficacy of its bioactive components on diverse cancer types and their mechanism of action and also summarizes the use of these phytochemicals for the purpose of developing a promising anticancer drug candidate in future.     

Fractionation of Pharmacologically Active Plant Polyphenols by Centrifugal Partition Chromatography

Abstract

Centrifugal partition chromatography (CPC) has been applied to the preparative fractionation of pharmacologically active polyphenols contained in the crude extracts from three medicinal plants. 1) (-)-Epigallocatechin gallate, the main component of tea polyphenols, which inhibits tumor promotion, 2) oligomeric hydrolyzable tannins, having host-mediated anti-tumor activity and antiviral activity, contained in Woodfordia fruticosa flower, 3) polyphenolic components of licorice, having anti-HIV activity. The results obtained with cartridges of medium volume and of small volume were compared during the fractionation of tea polyphenols.     

Chemical constituents and in vitro antioxidant activity of Phyllanthus wightianus

The whole plant of Phyllanthus wightianus (PW) was investigated for the antioxidant effects of three successive extracts: hexane (PWHE), chloroform (PWCE) and methanol (PWME), using standard in vitro models. The PWME exhibited a strong scavenging effect on 2,2-diphenyl-2-picryl hydrazyl (DPPH) free radicals and nitric oxide radical inhibition activity, due to possessing the highest content of tannins. The free radical scavenging effect of PWME was comparable with that of reference antioxidants. The extracts were subjected to isolation of their compounds: isomeric sterol mixture (1) [stigmasterol (1a), compesterol (1b) and β-sitosterol (1c)], fredilin (2), lupeol (3), gallic acid (4), bergenin (5), geraniin (6), corilagin (7) and ellagic acid (8) were established through the use of column chromatographic methods and spectral data. The percentage of tannins was also determined and estimated using the HPLC method. The data suggest that tannins are the active antioxidant compounds of P. wightianus. This study provides proof for the ethnomedical claims and reported biological activities of this plant. The plant therefore has very good therapeutic potential.     

Isolation and Purification of Condensed Tannins from Flamboyant Tree and Their Antioxidant and Antityrosinase Activities

Flamboyant tree, a kind of medicinal plant, was studied as a source of condensed tannins. The antioxidant activities of the condensed tannins from the leaf, fruit, and stem bark of flamboyant tree were screened by ABTS radical and hydroxyl radical scavenging activity methods. The results indicated that these compounds possessed potent antioxidant activity. Their structures were then characterized by high-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) after thiolytic degradation. The results showed that the leaf condensed tannins were composed of afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin, while the fruit and stem bark condensed tannins had afzelechin/epiafzelechin and catechin/epicatechin. In addition, the condensed tannins were evaluated for their antityrosinase ability. They were found to have significant antityrosinase activity. The IC₅₀ values were 35 ± 2.0 and 40 ± 0.5 μg/ml for the condensed tannins of fruit and stem bark, respectively. Further, fluorescence quenching and copper interacting techniques were utilized to unravel the molecular mechanisms of the inhibition. The results showed that the hydroxyl group of the condensed tannins could chelate the dicopper center of the enzyme and interact with tryptophan residues. Our studies revealed that condensed tannins might be suitable for use in food, agriculture, cosmetic, nutraceutical, and pharmaceutical applications.     

New potential and characterization of Andrographis paniculata L. Ness plant extracts as photoprotective agent

The species Andrographis paniculata L. Ness, family Acanthaceae grows in many parts in the island of Java in Indonesia. In this research, new potentials of photoprotective agents from A. paniculata plant extracts, along with their characteristics, were investigated. The phytochemical test, infrared analysis, ultraviolet characterization, fluorescence identification, flavonoid content by thin layer chromatography, high performance liquid chromatography-mass spectrometry (LCMS/MS) and photoprotective analysis were performed in the extracts. The new potentials of A. paniculata plant extracts were studied at various concentrations of extracts and shown by the value of the sun protection factor (SPF). Based on phytochemical test, A. paniculata plant extracts contained flavonoids, alkaloids, tannins, triterpenoids and polyphenols. A. paniculata plant extracts have 2 maximum wavelengths at 230 nm and 362 nm. The excitation peak at 300 nm (552.11 a.u) and the emission peak at 605 nm (516.02 a.u). The flavonoid content of the extracts was 0.022 µg/mL quercetin with Rf value of 0.61. The chromatogram of the LCMS/MS is similar to quercetin-3-glycoside standard at a retention time of 2.77. The photoprotective activity of A. paniculata plant extracts had ≥ 15 SPF. Its shows the possibility to use this extract as photoprotective agent in pharmaceutical preparations.     

Ellagitannin Digestion in Moth Larvae and a New Dimeric Ellagitannin from the Leaves of Platycarya strobilacea

Ellagitannins (ETs) are plant polyphenols with various health benefits. Recent studies have indicated that the biological activities of ETs are attributable to their degradation products, including ellagic acid and its gut microflora metabolites, such as urolithins. Insect tea produced in the Guangxi region, China, is made from the frass of moth larvae that feed on the ET-rich leaves of Platycarya strobilacea. Chromatographic separation of the Guangxi insect tea showed that the major phenolic constituents are ellagic acid, brevifolin carboxylic acid, gallic acid, brevifolin, and polymeric polyphenols. Chemical investigation of the feed of the larvae, the fresh leaves of P. strobilacea, showed that the major polyphenols are ETs including pedunculagin, casuarictin, strictinin, and a new ET named platycaryanin E. The new ET was confirmed as a dimer of strictinin having a tergalloyl group. The insect tea and the leaves of P. strobilacea contained polymeric polyphenols, both of which were shown to be composed of ETs and proanthocyanidins by acid hydrolysis and thiol degradation. This study clarified that Guangxi insect tea contains ET metabolites produced in the digestive tract of moth larvae, and the metabolites probably have higher bioavailabilities than the original large-molecular ETs of the leaves of P. strobilacea.     

Characterization and Identification of Bioactive Polyphenols in the Trapa bispinosa Roxb. Pericarp Extract

In this study, we present the isolation and characterization of the structure of six gallotannins (1–6), three ellagitannins (7–9), a neolignan glucoside (10), and three related polyphenolic compounds (gallic acid, 11 and 12) from Trapa bispinosa Roxb. pericarp extract (TBE). Among the isolates, the structure of compound 10 possessing a previously unclear absolute configuration was unambiguously determined through nuclear magnetic resonance and circular dichroism analyses. The α-glucosidase activity and glycation inhibitory effects of the isolates were evaluated. Decarboxylated rugosin A (8) showed an α-glucosidase inhibitory activity, while hydrolyzable tannins revealed stronger antiglycation activity than that of the positive control. Furthermore, the identification and quantification of the TBE polyphenols were investigated by high-performance liquid chromatography coupled to ultraviolet detection and electrospray ionization mass spectrometry analysis, indicating the predominance of gallic acid, ellagic acid, and galloyl glucoses showing marked antiglycation properties. These findings suggest that there is a potential food industry application of polyphenols in TBE as a functional food with antidiabetic and antiglycation activities.     

The Analysis of Phenolic Compounds in Walnut Husk and Pellicle by UPLC-Q-Orbitrap HRMS and HPLC

Husk and pellicle as the agri-food waste in the walnut-product industry are in soaring demand because of their rich polyphenol content. This study investigated the differential compounds related to walnut polyphenol between husk and pellicle during fruit development stage. By using ultra-high performance liquid chromatography-quadrupole-orbitrap (UHPLC-Q-Orbitrap), a total of 110 bioactive components, including hydrolysable tannins, flavonoids, phenolic acids and quinones, were tentatively identified, 33 of which were different between husk and pellicle. The trend of dynamic content of 16 polyphenols was clarified during walnut development stage by high-performance liquid chromatography (HPLC). This is the first time to comprehensive identification of phenolic compounds in walnut husk and pellicle, and our results indicated that the pellicle is a rich resource of polyphenols. The dynamic trend of some polyphenols was consistent with total phenols. The comprehensive characterization of walnut polyphenol and quantification of main phenolic compounds will be beneficial for understanding the potential application value of walnut and for exploiting its metabolism pathway.     

Association of tannins and related polyphenols with the cyclic peptide gramicidin S

The association of 10 different tannins and related polyphenols with gramicidin S, a cyclic peptide having a rigid beta-turn structure, has been examined using 1H-NMR spectroscopy. In the presence of pentagalloylglucose and epigallocatechin-3-O-gallate, the proton signals due to proline and the adjacent phenylalanine moieties selectively shifted to up field, suggesting a regioselective association with the beta-turn structure. The association was also supported by the observation of intermolecular nuclear Overhauser effects between epigallocatechin-3-O-gallate and the peptide. In contrast, ellagitannins, biogenetically derived from pentagalloylglucose, showed small and non-selective chemical shift changes, suggesting that interaction with these tannins is relatively weak. The hydrophobicity of the tannin molecules and the steric hindrance of the interaction site are thought to be important in the association.     

Multiconstituent identification in root,branch, and leaf extracts of Juglans mandshurica using ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry

As a traditional medicinal plant, Juglans mandshurica has been used for the treatment of cancer. Different organs of this plant showed anti‐tumor activity in clinic and laboratory. Comparative identification of constituents in different plant organs is essential for investigation of the relationship between chemical constituents and pharmacological activities. For this aim, the roots, branches, and leaves of J. mandshurica were extracted with 50% v/v methanol and then subjected to ultra‐high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry analysis conducted under low and high energy. As a result, we have to date identified 111 compounds consisting of 56 tannins, 29 flavonoids, 13 organic acids, 8 naphthalene derivatives, and 5 anthracenes. Five compounds, namely, diquercetin trihydroxy‐truxinoyl‐glucoside, two quercetin kaempferol dihydroxy‐truxinoyl‐glucosides, syringoyl‐tri‐galloyl‐O‐glucose, and dihydroxy‐naphthalene syringoyl‐glucoside, were tentatively identified as new compounds. Of the compounds identified, 76 were found in the root extract, 67 in the branch extract, and 37 in the leaf extract. Only six compounds including four organic acids and two tannins were found in all three extracts. We developed a rapid and sensitive ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry approach to identify multiple constituents of complex extracts without separation and ion selection. The results presented provide useful information on further research of the bioactive compounds of J. mandshurica .     

Effects of interaction of tannins with co-existing substances. VII. Inhibitory effects of tannins and related polyphenols on xanthine oxidase

The inhibitory effects of hydrolyzable tannins, condensed tannins and related polyphenols on the activity of xanthine oxidase (XOD), catalyzing uric acid formation from xanthine, were investigated. Marked differences in the strength of the inhibition were observed. Some of the differences among the monomeric hydrolyzable tannins were due to their molecular weights, reflecting the number of phenolic hydroxyl groups in the molecule. However, the inhibitory activity of several oligomeric hydrolyzable tannins seemed particularly low in spite of their large molecular size. It was also observed that differences in location of acyl groups on the carbohydrate cores caused differences in the inhibitory activity among monomeric and oligomeric hydrolyzable tannins. A caffeic acid derivative (caffeetannin), 3,5-di-O-caffeoylquinic acid (24), also inhibited this enzyme. Galloylation and the degree of polymerization in proanthocyanidins were also shown to affect remarkably the strength of the inhibition. Among the compounds tested in the present study, valoneic acid dilactone (29), isolated from Mallotus japonicus, inhibited the enzyme most effectively. A kinetic study showed that this dilactone inhibited XOD non-competitively. Comparison of the inhibitory effect on XOD, with the binding activity to hemoglobin, for each tannin, suggests that their inhibition of XOD is not based on non-specific binding to the protein. Similar comparison of the inhibitory effect on XOD with the inhibitory effect on the generation of superoxide anion radical (O2-.) from the hypoxanthine-XOD system revealed that the inhibition of O2-. generation by tannins is due to their radical-scavenging activity, and not due to their inhibitory activity upon the enzyme.     

Thermal properties of tannin extracted from Anacardium occidentale L. using TGA and FT-IR spectroscopy

The chemical nature of the polyphenols of cashew kernel testa has been determined. Testa contains tannins, which present large molecular complexity and has an ancient use as tanning agents. The use of tannins extracted from cashew testa, considered in many places as a waste, grants an extra value to the cashew. In this work we have analysed through high performance liquid chromatography, infrared spectroscopy (FT-IR) and thermo gravimetric analysis the average molecular weight, main functional groups and thermal properties of tannins extracted from Anacardium occidentale L. The results of these analyses are compared with the commercial grade tannic acid. The FT-IR spectra showed bands characteristic of C = C, C–C and OH bonds. This important bioactive compound present in the cashew nut kernel testa was suggested as an interesting economical source of antioxidants for use in the food and nutraceutical industry.     

Nephroprotective Effects of Alhagi camelorum against Cisplatin-Induced Nephrotoxicity in Albino Wistar Rats

Alhagi camelorum (AC) is an old plant with a significant therapeutic value throughout Africa, Asia, and Latin America. The overuse of cisplatin (Cis > 50 mg/m²) is associated with observed nephrotoxicity, ototoxicity, gastrotoxicity, myelosuppression, and allergic reactions. Remedial measures are needed for the protection of nephrotoxicity against cisplatin. Thus, we investigated the nephroprotective effects of AC plant extract to prevent cisplatin-induced nephrotoxicity in albino Wistar rats. The presence of polyphenols, phenolic compounds, tannins, and saponins was revealed during phytochemical investigation, and a significantly intense antioxidant activity was recorded. There were no toxicological symptoms in the treated rats, and no anatomical, physiological, or histological abnormalities were found compared to the control rats. The results of correcting cisplatin-induced nephrotoxicity revealed that the extract has a significant ability to treat kidney damage, with most parameters returning to normal after only three weeks of therapy. It is concluded that co-administration of cisplatin with AC extract showed exceptional nephroprotective effects at a dose of 600 mg/kg for Cis-induced nephrotoxicity.