Bioactive compounds in flowers and fruits of Sambucus nigra L.
Appears in the following Collection
- Farmasøytisk institutt 
AbstractSambucus nigra L. or black elder has a long history of use in traditional European medicine for treatment of inflammations, infections, diabetes and for boosting the immune system. The aim of this thesis was to investigate the potential health benefits of elderberries and elderflowers with main focus on the immunomodulatory effects and the anti-diabetic potential of pectic polysaccharides and phenolic constituents. Pectic polysaccharides isolated from the 50% EtOH, 50 °C and 100 °C water extracts from the elderberries and the elderflowers were shown to contain homogalacturonan (HG), rhamnogalacturonan-I (RG-I), arabinogalactan-I (AG-I) and arabinogalactan-II (AG-II), in addition to arabinans. Rhamnogalacturonan-II (RG-II) was only present in some of the elderflower fractions. The distribution of sugar residues, molecular weight, and their linkages varied between the fractions. Weak acid hydrolysis was performed on the most active acidic fractions from the elderberries and the elderflowers. An almost complete loss of Ara was observed, the amount of some linkages to Rha and Gal were also decreased. A negative Yariv test after weak acid hydrolysis indicated a degradation of AG-II. Ester groups in the polysaccharide fractions from the elderflowers were reduced after treatment with NaOH. The de-esterified polysaccharides showed the same distribution of linkages as their respective native polysaccharides. In order to isolate the hairy regions, one acidic fraction from elderberries (SnBe50-I-S3) and four acidic fractions from elderflowers (SnFl-50-I-S2, 50WSnFl-I-S2, 100WSnFl-I-S2, 100WSnFl-I-S3) were treated with endo-polygalacturonase. This led to the isolation of five sub-fractions from the elderberry fraction and two sub-fractions from each of the elderflower fractions. RG-I like structure and side chains of AG-I and AG-II were the predominant part in the isolated sub-fraction-I and sub-fraction-II from the elderberries and in the sub-fractions-I from the elderflowers. These fractions showed high degree of branch points compared to the native fractions. Sub-fractions-II from the elderflowers consisted of RG-I and also small amounts of RG-II structures. Complement and macrophages are both part of the innate and adaptive immune system. All the acidic polysaccharide fractions from elderberries and elderflowers showed dose-dependent complement fixating activity and stimulated nitric oxide (NO) production in RAW 264.7 macrophages, with elderflower fractions being the most active ones. Removal of Ara and reduced side chain complexity contributed to reduced activity, while removal of ester led to an increased activity compared to the native fractions. The hairy regions isolated after enzymatic treatment possessed strong complement fixating and macrophage stimulating activity, much stronger than the native fractions, whereas the smooth regions showed a reduced activity. Type 2 diabetes is one of the most prevalent and serious metabolic diseases, and is associated with hyperglycemia, insulin resistance and dysregulation of glucose- and fatty acid uptake. Elderberry and elderflower crude extracts, flavonoids, phenolic acids and metabolites showed a dose-dependent increase of glucose- and fatty acid uptake in human skeletal muscle cells and human liver cells. A high increase of glucose- and fatty acid uptake observed after exposure to selected intestinal metabolites (protocatechuic acid, phloroglucinol aldehyde, caffeic acid, ferulic acid) is of interest, since they are better absorbed from the intestine compared to the native polyphenols and therefore easier will reach the systemic tissues. Several of the crude extracts and phenolic constituents from elderberries and elderflowers were found to be strong α-amylase and α-glucosidase inhibitors compared to the anti-diabetic drug acarbose. Oxidative stress is associated with the pathogenesis of diabetes and inflammation. In general, the phenolic substances showed strong radical scavenging and 15-lipoxygenase inhibitory effects, but were less active toward xanthine oxidase. The dichlorometane and water extracts from both the elderberries and elderflowers were inactive as antioxidants in contrast to the alcohol extracts, which possessed high or moderate antioxidant activities. The phenolic-rich extracts from the elderberries and the elderflowers showed potent anti-inflammatory activity as they showed high complement fixating activity and inhibited NO-production in LPS activated RAW 264.7 macrophages and dendritic D2SC/I cells. Flavonoids and phenolic acids were all NO inhibitors, with variation in activity from one compound to the other. The metabolites were inactive in the complement fixating test, but possessed rather strong NO inhibitory activity both in the macrophages and the dendritic cells. These results showed that polysaccharides and polyphenols from elderberries and elderflowers have potential health promoting effects. Intake of elderberries and elderflowers might help to regulate inflammatory diseases, and might give potential anti-diabetic and immune-stimulating effects.
List of papers
|I. Giang Thanh Thi Ho, Abeeda Ahmed, Yuan-Feng Zou, Torun Helene Aslaksen, Helle Wangensteen & Hilde Barsett. Structure-activity relationship of immunomodulating pectins from elderberries. Carbohydrate Polymers 2015, 125, 314-322. The paper is not available in DUO. The published version is available at: https://doi.org/10.1016/j.carbpol.2015.02.057|
|II. Giang Thanh Thi Ho, Yuan-Feng Zou, Torun Helene Aslaksen, Helle Wangensteen & Hilde Barsett. Structural characterization of bioactive pectic polysaccharides from elderflowers (Sambuci flos). Carbohydrate Polymers 2016, 135, 128-137. The paper is not available in DUO. The published version is available at: https://doi.org/10.1016/j.carbpol.2015.08.056|
|III. Giang Thanh Thi Ho, Yuan-Feng Zou, Helle Wangensteen & Hilde Barsett. RG-I regions from elderflower pectins substituted on GalA are strong immunomodulators. International Journal of Biological Macromolecules 2016, 92, 731-738. The paper is not available in DUO. The published version is available at: https://doi.org/10.1016/j.ijbiomac.2016.07.090|
|IV. Giang Thanh Thi Ho, Eili Tranheim Kase, Helle Wangensteen & Hilde Barsett. Effect of phenolic compounds from elderflowers on glucose- and fatty acid uptake in human myotubes and HepG2-Cells. Molecules 2017, 22(90), 1-15. The paper is available in DUO: http://urn.nb.no/URN:NBN:no-61031|
|V. Giang Thanh Thi Ho, Eili Tranheim Kase, Helle Wangensteen & Hilde Barsett. Phenolic elderberry extracts, anthocyanins, procyanidins and metabolites influence glucose and fatty acid uptake in human skeletal muscle cells. Journal of Agricultural and Food Chemistry 2017, 65, 2677-2685. The paper is not available in DUO. The published version is available at: https://doi.org/10.1021/acs.jafc.6b05582|
|VI. Giang Thanh Thi Ho, Thi Kim Yen Nguyen, Eili Tranheim Kase, Margey Tadesse, Hilde Barsett & Helle Wangensteen. Enhanced Glucose Uptake in Human Liver Cells and Inhibition of Carbohydrate Hydrolyzing Enzymes by Nordic Berry Extracts. Molecules 2017, 22(10), 1806. The paper is available in DUO: http://hdl.handle.net/10852/58966|
|VII. Giang Thanh Thi Ho, Helle Wangensteen & Hilde Barsett. Elderberry and elderflower extracts, phenolic compounds and metabolites with effect on complement, RAW 264.7 macrophages and dendritic cells. International Journal of Molecular Sciences 2017, 18(3), 584, 1-17. The paper is available in DUO: http://urn.nb.no/URN:NBN:no-61032|