Polyphenols of the Inuleae-Inulinae and Their Biological Activities: A Review.

Polyphenols are ubiquitous plant metabolites that demonstrate biological activities essential to plant-environment interactions. They are of interest to plant food consumers, as well as to the food, pharmaceutical and cosmetic industry. The class of the plant metabolites comprises both widespread (chlorogenic acids, luteolin, quercetin) and unique compounds of diverse chemical structures but of the common biosynthetic origin. Polyphenols next to sesquiterpenoids are regarded as the major class of the Inuleae-Inulinae metabolites responsible for the pharmacological activity of medicinal plants from the subtribe (Blumea spp., Dittrichia spp., Inula spp., Pulicaria spp. and others). Recent decades have brought a rapid development of molecular and analytical techniques which resulted in better understanding of the taxonomic relationships within the Inuleae tribe and in a plethora of data concerning the chemical constituents of the Inuleae-Inulinae. The current taxonomical classification has introduced changes in the well-established botanical names and rearranged the genera based on molecular plant genetic studies. The newly created chemical data together with the earlier phytochemical studies may provide some complementary information on biochemical relationships within the subtribe. Moreover, they may at least partly explain pharmacological activities of the plant preparations traditionally used in therapy. The current review aimed to systematize the knowledge on the polyphenols of the Inulae-Inulinae.

Hairy Root Cultures as a Source of Phenolic Antioxidants: Simple Phenolics, Phenolic Acids, Phenylethanoids, and Hydroxycinnamates.

Plant-derived antioxidants are intrinsic components of human diet and factors implicated in tolerance mechanisms against environmental stresses in both plants and humans. They are being used as food preservatives and additives or ingredients of cosmetics. For nearly forty years, Rhizobium rhizogenes-transformed roots (hairy roots) have been studied in respect to their usability as producers of plant specialized metabolites of different, primarily medical applications. Moreover, the hairy root cultures have proven their value as a tool in crop plant improvement and in plant secondary metabolism investigations. Though cultivated plants remain a major source of plant polyphenolics of economic importance, the decline in biodiversity caused by climate changes and overexploitation of natural resources may increase the interest in hairy roots as a productive and renewable source of biologically active compounds. The present review examines hairy roots as efficient producers of simple phenolics, phenylethanoids, and hydroxycinnamates of plant origin and summarizes efforts to maximize the product yield. Attempts to use Rhizobium rhizogenes-mediated genetic transformation for inducing enhanced production of the plant phenolics/polyphenolics in crop plants are also mentioned.

Constituents of Pulicaria inuloides and Cytotoxic Activities of Two Methoxylated Flavonols.

Plants of the genus Pulicaria are known for providing traditional medicines, spices, herbal teas, and insect deterrents. Pulicaria inuloides (Poir.). DC. is one of the less chemically studied species within the genus. Hydroalcoholic extracts from roots and aerial parts of P. inuloides were analyzed using the UHPLC-PAD-MSn technique and revealed the presence of six caffeoylquinic and eleven caffeoylhexaric conjugates together with hydroxykaempferol dimethyl ether and quercetagetin trimethyl ether. Moreover, constituents of chloroform extract from the whole P. inuloides plants were isolated and identified by spectroscopic methods. One new and four known caryophyllene derivatives, three thymol derivatives, and four polymethoxylated flavonols were found in the analyzed extract. The structure of the new compound was established by spectroscopic methods (HRESIMS, 1H NMR, 13C NMR, COSY, HSQC, HMBC, NOESY). The cytotoxicity of 6-Hydroxykaempferol 3,7-dimethyl ether and quercetagetin 3,7,3'-trimethyl ether (chrysosplenol C), which are major flavonols isolated from the plant, were tested on prostate epithelial cells (PNT2), prostate cancer cells (DU145 and PC3), human keratinocytes (HaCaT), and melanoma cells (HTB140 and A375). Both flavonols demonstrated moderate cytotoxic activity against PC3 cells (IC50 = 59.5 µM and 46.6 µM, respectively). The remaining cell lines were less affected (IC50 > 150 µM).

Chemical Composition and Cytotoxic Activity of Extracts from Carpesium divaricatum: In Vitro- versus Field-Grown Plants.

Carpesium divaricatum Sieb. & Zucc. is a plant species rich in terpenoids of anti-inflammatory and cytotoxic activity, especially germacranolides of potential medicinal value. The present study describes in vitro multiplication of C. divaricatum, analysis of active constituents in the multiple shoots, and assessment of cytotoxic activities of extracts prepared from in vitro- and field-grown plants. The plant extracts were evaluated for cytotoxicity using two melanoma cell lines (HTB140 and A375); human keratinocytes (HaCaT); two colon cancer cell lines (Caco2 and HT29); human hepatocellular carcinoma cells (HepG2); two lines of prostate cancer cells (DU145 and PC3) and prostate epithelial cells (PNT2). Chemical compositions of the assayed extracts were analyzed by HPLC/DAD, in reference to isolated compounds. Maximum of 4.07 ± 1.61 shoots regenerated from a nodal explant of C. divaricatum, cultivated in a liquid MS medium supplemented with thidiazuron (1 µM). In vitro grown shoots and plantlets of C. divaricatum accumulated terpenoids that are known as active constituents of the intact plant. Cytotoxic activity of the extracts prepared from the in vitro cultured plants was like that demonstrated by the extracts prepared from field-grown plants and seemed to be more selective than cytotoxicities of the individual germacranolides.

Hairy Root Cultures as a Source of Polyphenolic Antioxidants: Flavonoids, Stilbenoids and Hydrolyzable Tannins.

Due to their chemical properties and biological activity, antioxidants of plant origin have gained interest as valuable components of the human diet, potential food preservatives and additives, ingredients of cosmetics and factors implicated in tolerance mechanisms against environmental stress. Plant polyphenols are the most prominent and extensively studied, albeit not only group of, secondary plant (specialized) metabolites manifesting antioxidative activity. Because of their potential economic importance, the productive and renewable sources of the compounds are desirable. Over thirty years of research on hairy root cultures, as both producers of secondary plant metabolites and experimental systems to investigate plant biosynthetic pathways, brought about several spectacular achievements. The present review focuses on the Rhizobium rhizogenes-transformed roots that either may be efficient sources of plant-derived antioxidants or were used to elucidate some regulatory mechanisms responsible for the enhanced accumulation of antioxidants in plant tissues.

Sorbus intermedia (EHRH.) PERS. fruits as a novel source of biologically active triterpenoids - Comparative studies of ursolic acid derivatives with cytotoxic potential.

In the current study, the fruits of a popular ornamental tree, Sorbus intermedia, were investigated phytochemically and biologically as potential source of bioactive triterpenes. Six terpenoids were isolated and examined with respect to their cytotoxic activity using a broad screening in vitro model and multivariate analysis for better demonstration of the effects on cancer cells. This chemometric approach allowed us to confirm that the structural characteristics of the compounds significantly affected their impact on cell lines. Ursolic acid was found to be the most potent cytotoxic agent with IC50 predominantly < 10 µg/mL after 24 h of incubation. Its 3-acetoxy derivative was less active, however, an improvement in selectivity with regard to prostate panel was observed. Reduction of the carboxylic moiety at C28, as well as introduction of the hydroxyl group at 19α position led to complete loss of cytotoxic activity.

New Polyesterified Ursane Derivatives from Leaves of Maesa membranacea and Their Cytotoxic Activity.

Maesa membranacea A. DC. (Primulaceae) is a plant species that has been frequently used by practitioners of the traditional ethnobotany knowledge from northern and central Vietnam. However, the chemical constituents of the plant remained unknown until recently. Chromatographic separation of a chloroform-soluble fraction of extract from leaves of M. membranacea led to the isolation of two new polyesterified ursane triterpenes (1-2) and two known apocarotenoids: (+)-dehydrovomifoliol (3) and (+)-vomifoliol (4). The chemical structures of the undescribed triterpenoids were elucidated using 1D and 2D MNR and HRESIMS spectral data as 2α,6ß,22α-triacetoxy-11α-(2-methylbutyryloxy)-urs-12-ene-3α,20ß-diol (1) and 2α,6ß,22α-triacetoxy-urs-12-ene-3α,11α,20ß-triol (2). The newly isolated triterpenoids were tested for their cytotoxic activity in vitro against two melanoma cell lines (HTB140 and A375), normal skin keratinocytes (HaCaT), two colon cancer cell lines (HT29 and Caco-2), two prostate cancer cell lines (DU145 and PC3) and normal prostate epithelial cells (PNT-2). Doxorubicin was used as a reference cytostatic drug. The 2α,6ß,22α-triacetoxy-11α-(2-methylbutyryloxy)-urs-12-ene-3α,20ß-diol demonstrated cytotoxic activity against prostate cancer cell lines (Du145-IC50 = 35.8 µg/mL, PC3-IC50 = 41.6 µg/mL), and at a concentration of 100 µg/mL reduced viability of normal prostate epithelium (PNT-2) cells by 41%.

Neuroprotective Properties of Kempferol Derivatives from Maesa membranacea against Oxidative Stress-Induced Cell Damage: An Association with Cathepsin D Inhibition and PI3K/Akt Activation.

As components of the human diet with potential health benefits, flavonols are the subject of numerous studies, confirming their antioxidant, free radical scavenging and anti-inflammatory activity. Taking into consideration the postulated pathogenesis of certain CNS dysfunctions characterized by neuronal degradation, flavonols may prevent the decay of neurons in multiple pathways. Leaves of Maesa membranacea yielded several flavonol glycosides including α-rhamnoisorobin (kaempferol 7-O-α-rhamnoside) and kaempferitrin (kaempferol 3,7-di-O-α-rhamnoside). The latter compound was a major constituent of the investigated plant material. Neuroprotective effects of kaempferitrin and α-rhamnoisorobin were tested in vitro using H2O2-, 6-OHDA- and doxorubicin-induced models of SH-SY5Y cell damage. Both undifferentiated and differentiated neuroblastoma cells were used in the experiments. α-Rhamnoisorobin at a concentration range of 1-10 µM demonstrated cytoprotective effects against H2O2-induced cell damage. The compound (at 1-10 µM) was also effective in attenuating 6-OHDA-induced neurotoxicity. In both H2O2- and 6-OHDA-induced cell damage, kaempferitrin, similar to isoquercitrin, demonstrated neuroprotective activity at the highest of the tested concentrations (50 µM). The tested flavonols were not effective in counteracting doxorubicin-induced cytotoxicity. Their caspase-3- and cathepsin D-inhibitory activities appeared to be structure dependent. Inhibition of the PI3-K/Akt pathway abolished the neuroprotective effect of the investigated flavonols.

Germacranolides from Carpesium divaricatum: Some New Data on Cytotoxic and Anti-Inflammatory Activity.

Carpesium divaricatum Sieb. & Zucc., a traditional medicinal plant used as an inflammation-relieving remedy, is a rich source of terpenoids. At least 40 germacrane-type sesquiterpene lactones, representatives of four different structural groups, were isolated from the plant. Cytotoxicity against cancer cells in vitro is the most frequently described biological activity of the compounds. However, little is known about the selectivity of the cytotoxic effect. The anti-inflammatory activity of the germacranolides is also poorly documented. The objective of the present study was to assess the cytotoxic activity of selected C. divaricatum germacranolides-derivatives of 4,5,8,9-tetrahydroxy-3-oxo-germacran-6,12-olide towards cancer and normal cell lines (including cells of different p53 status). Moreover, to assess the anti-inflammatory effect of the compounds, the release of four proinflammatory cytokines/chemokines (IL-1ß, IL-8, TNF-α and CCL2) by lipopolysaccharide-stimulated human neutrophils was measured by ELISA. The investigated sesquiterpene lactones demonstrated nonselective activity towards prostate cancer (Du145 and PC3) and normal prostate epithelial cells (PNT2) as well as against melanoma cells (A375 and HTB140) and keratinocytes (HaCaT). Cytotoxic activity against osteosarcoma cells was independent of their p53 status. In sub-cytotoxic concentrations (0.5-2.5 µM) the studied compounds significantly decreased cytokine/chemokine release by lipopolysaccharide-stimulated human leukocytes.

Neuroprotective Effects of Methyl Caffeate against Hydrogen Peroxide-Induced Cell Damage: Involvement of Caspase 3 and Cathepsin D Inhibition.

Finding effective neuroprotective strategies to combat various neurodegenerative disorders still remain a clinically unmet need. Methyl caffeate (MC), a naturally occurring ester of caffeic acid, possesses antioxidant and anti-inflammatory activities; however, its role in neuroprotection is less investigated. In order to better characterize neuroprotective properties of MC, we tested its effectiveness in various models of neuronal cell injury in human neuroblastoma SH-SY5Y cells and in mouse primary neuronal cell cultures. MC at micromolar concentrations attenuated neuronal cell damage induced by hydrogen peroxide (H2O2) in undifferentiated and neuronal differentiated SH-SY5Y cells as well as in primary cortical neurons. This effect was associated with inhibition of both caspase-3 and cathepsin D but without involvement of the PI3-K/Akt pathway. MC was neuroprotective when given before and during but not after the induction of cell damage by H2O2. Moreover, MC was protective against 6-OHDA-evoked neurotoxicity in neuronal differentiated SH-SY5Y cells via inhibition of necrotic and apoptotic processes. On the other hand, MC was ineffective in models of excitotoxicity (induced by glutamate or oxygen-glucose deprivation) and even moderately augmented cytotoxic effects of the classical apoptotic inducer, staurosporine. Finally, in undifferentiated neuroblastoma cells MC at higher concentrations (above 50 microM) induced cell death and when combined with the chemotherapeutic agent, doxorubicin, it increased the cell damaging effects of the latter compound. Thus, neuroprotective properties of MC appear to be limited to certain models of neurotoxicity and depend on its concentrations and time of administration.

Carpesium divaricatum Sieb. & Zucc. Revisited: Newly Identified Constituents from Aerial Parts of the Plant and Their Possible Contribution to the Biological Activity of the Plant.

Carpesium divaricatum Sieb. & Zucc. has a long history of use as both a medicinal and a food plant. However, except for terpenoids, its chemical constituents have remained poorly investigated. The composition of hydroalcoholic extract from aerial parts of C. divaricatum was analyzed by HPLC-DAD-MSn, revealing the presence of numerous caffeic acid derivatives that were formerly unknown constituents of the plant. In all, 17 compounds, including commonly found chlorogenic acids and rarely occurring butyryl and methylbutyryl tricaffeoylhexaric acids, were tentatively identified. Fractionation of lipophilic extract from cultivated shoots led to the isolation of 12-oxo-phytodienoic acid (12-OPDA), which is a newly identified constituent of the plant. The compound, at concentrations of 0.5, 1.0, and 2.5 µM, significantly reduced IL-8, IL-1ß, TNFα, and CCL2 excretion by lipopolysaccharide (LPS)-stimulated human neutrophils. Reactive oxygen species (ROS) production induced by f-MLP was also significantly diminished in the neutrophils pretreated by 12-OPDA. The newly identified constituents of the plant seem to be partly responsible for its pharmacological activity and elevate the value of C. divaricatum as a potential functional food.

Major terpenoids from Telekia speciosa flowers and their cytotoxic activity in vitro.

In addition to known constituents of Telekia speciosa, an acetone extract from ray florets of the plant yielded: 5,5'-dibutoxy-2,2'-bifuran (1), 5,5'-diisobutoxy-2,2'-bifuran (2), α-tocopherol (3), ß-tocopherol (4), loliolide palmitate (5), a mixture of calenduladiol esters - 16ß-hydroxylupeol-3-O-palmitate (7) and 16ß-hydroxylupeol-3-O-myristate (8), 1-epiinuviscolide (12), inuviscolide (13), 3-epiisotelekin (16), 4α-hydroxy-9ß,10ß-epoxy-1ß(H)-11(13)-guaien-8α,12-olide (17), 4α-hydroxy-1ß(H)-9(10),11(13)-guaiadien-8α,12-olide (18), loliolide (19) and 4ß,10ß-dihydroxy-1α(H),5α(H)-11(13)-guaien-8α,12-olide (20). Calenduladiol esters and asperilin (14) were the major constituents of the extract. Their cytotoxic effect on human normal prostate epithelial cells (PNT-2), human prostate carcinoma cell lines, human skin fibroblasts (HSF) and human melanoma cell lines was examined in vitro. Triterpene esters showed no cytotoxicity against nearly all cell lines tested, except for Du145 prostate carcinoma cells (IC50 - 62.0 µΜ). Asperilin displayed activity against the cell lines under study, especially against three tested lines of melanomas (A375, IC50 - 17.6 µΜ, WM793, IC50 - 28.2 µΜ and Hs 294T, IC50 - 29.5 µΜ).

Root tubers of Lactuca tuberosa as a source of antioxidant phenolic compounds and new furofuran lignans.

From the root tubers of Lactuca tuberosa, a wild edible plant species, nine phenolic compounds were isolated, including two new furofuran lignan glucosides, named lactuberin A and lactuberin B. Their structures were elucidated by spectroscopic methods, especially HRESIMS and 2D NMR techniques. This is the first time that compounds belonging to the epi series of 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane type furofuran lignans have been found in Lactuca species. The total phenolic content of the root tuber extract was evaluated and its major phenolic constituents, caffeic acid, chlorogenic acid and 3,5 dicaffeoylquinic acid, known to possess antioxidant activity, were quantified. Additionally, the root tuber extract showed DPPH radical scavenging activity implying its potential as functional food.

Simultaneous quantification of eudesmanolides and thymol derivatives from tissues of Inula helenium and I. royleana by reversed-phase high-performance liquid chromatography.

A simple and rapid isocratic reversed-phase high-performance liquid chromatographic method for the quantification of alantolactone/isoalantolactone and three thymol derivatives in roots and root cultures of Inula helenium and I. royleana has been developed. The method could be applied to screen raw materials in search for highly productive plants and in vitro cultures.