Biomedical subjects

K Ingólfsdóttir

Publications and source records attributed to K Ingólfsdóttir.

6 recordsLinked to original sources

PubMed2004

Anti-proliferative lichen compounds with inhibitory activity on 12(S)-HETE production in human platelets.

Several lichen compounds, i.e. lobaric acid (1), a beta-orcinol depsidone from Stereocaulon alpinum L., (+)-protolichesterinic acid (2), an aliphatic alpha-methylene-gamma-lactone from Cetraria islandica Laur. (Parmeliaceae), (+)-usnic acid (3), a dibenzofuran from Cladonia arbuscula (Wallr.) Rabenh. (Cladoniaceae), parietin (4), an anthraquinone from Xanthoria elegans (Link) Th. Fr. (Calaplacaceae) and baeomycesic acid (5), a beta-orcinol depside isolated from Thamnolia vermicularis (Sw.) Schaer. var. subuliformis (Ehrh.) Schaer. were tested for inhibitory activity on platelet-type 12(S)-lipoxygenase using a cell-based in vitro system in human platelets. Lobaric acid (1) and (+)-protolichesterinic acid (2) proved to be pronounced inhibitors of platelet-type 12(S)-lipoxygenase, whereas baeomycesic acid (5) showed only weak activity (inhibitory activity at a concentration of 100 microg/ml: (1) 93.4+/-6.62%, (2) 98,5+/-1.19%, 5 14.7+/-2.76%). Usnic acid (3) and parietin (4) were not active at this concentration. 1 and 2 showed a clear dose-response relationship in the range of 3.33-100 microg/ml. According to the calculated IC50 values the highest inhibitory activity was observed for the depsidone 1 (IC50 = 28.5 microM) followed by 2 (IC50 = 77.0 microM). The activity of 1 was comparable to that of the flavone baicalein, which is known as a selective 12(S)-lipoxygenase inhibitor (IC50 = 24.6 microM).

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗

PubMed2002

Usnic acid.

Since its first isolation in 1844, usnic acid [2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzo-furandione] has become the most extensively studied lichen metabolite and one of the few that is commercially available. Usnic acid is uniquely found in lichens, and is especially abundant in genera such as Alectoria, Cladonia, Usnea, Lecanora, Ramalina and Evernia. Many lichens and extracts containing usnic acid have been utilized for medicinal, perfumery, cosmetic as well as ecological applications. Usnic acid as a pure substance has been formulated in creams, toothpaste, mouthwash, deodorants and sunscreen products, in some cases as an active principle, in others as a preservative. In addition to antimicrobial activity against human and plant pathogens, usnic acid has been shown to exhibit antiviral, antiprotozoal, antiproliferative, anti-inflammatory and analgesic activity. Ecological effects, such as antigrowth, antiherbivore and anti-insect properties, have also been demonstrated. A difference in biological activity has in some cases been observed between the two enantiomeric forms of usnic acid. Recently health food supplements containing usnic acid have been promoted for use in weight reduction, with little scientific support. The emphasis of the current review is on the chemistry and biological activity of usnic acid and its derivatives in addition to rational and ecologically acceptable methods for provision of this natural compound on a large scale.

Analgesics↗

PubMed2002

Effects of tenuiorin and methyl orsellinate from the lichen Peltigera leucophlebia on 5-/15-lipoxygenases and proliferation of malignant cell lines in vitro.

The orcinol derivatives tenuiorin (1) and methyl orsellinate (2) were identified as active components of an extract from the lichen Peltigera leucophlebia (Nyl.) Gyeln. showing in vitro inhibitory activity against 15-lipoxygenase from soybeans. The compounds were subsequently tested for in vitro activity against 5-lipoxygenase from porcine leucocytes and proved to be moderately active, with IC50 values of 41.6 microM and 59.6 microM respectively. Tenuiorin is a known constituent of several Peltigera species but has not previously been isolated from P. leucophlebia. As correlation between 5-lipoxygenase inhibition and antiproliferative effects has earlier been witnessed for related lichen metabolites, tenuiorin and methyl orsellinate were further tested for antiproliferative activity on cultured human breast (T-47D)-, pancreatic (PANC-1)- and colon (WIDR) cancer cell lines. The monomeric methyl orsellinate exhibited no detectable antiproliferative activity whereas the trimeric tenuiorin caused moderate/weak reduction in [3H]-thymidine uptake of the pancreatic- and colon cancer cells, with ED50 values of 87.9 and 98.3 microM respectively.

Breast Neoplasms↗

PubMed1998

Antimycobacterial activity of lichen metabolites in vitro.

Several compounds, whose structures represent the most common chemical classes of lichen metabolites, were screened for in vitro activity against Mycobacterium aurum, a non-pathogenic organism with a similar sensitivity profile to M. tuberculosis. Of the compounds tested, usnic acid from Cladonia arbuscula exhibited the highest activity with an MIC value of 32 microg/ml. Atranorin and lobaric acid, both isolated from Stereocaulon alpinum, salazinic acid from Parmelia saxatilis and protolichesterinic acid from Cetraria islandica all showed MIC values >/=125 microg/ml.

4-Butyrolactone↗

PubMed1998

Anti-proliferative effects of lichen-derived inhibitors of 5-lipoxygenase on malignant cell-lines and mitogen-stimulated lymphocytes.

Several lichen species have been used traditionally as medicinal plants. It has previously been shown that two low-molecular-weight lichen metabolites, lobaric acid isolated from Stereocaulon alpinum Laur. and protolichesterinic acid isolated from Cetraria islandica L. (Ach.), have in-vitro inhibitory effects on arachidonate 5-lipoxygenase. We have studied the effects of these compounds on cultured cells from man, including three malignant cell-lines (T-47D and ZR-75-1 from breast carcinomas and K-562 from erythro-leukaemia), as well as normal skin fibroblasts and peripheral blood lymphocytes. Both test substances caused a significant reduction in DNA synthesis, as measured by thymidine uptake, in all three malignant cell-lines; the dose inducing 50% of maximum inhibition (ED50) was between 1.1 and 24.6 microg mL(-1) for protolichesterinic acid and between 14.5 and 44.7 microg mL(-1) for lobaric acid. The breast-cancer cell-lines were more sensitive than K-562. The proliferative response of mitogen-stimulated lymphocytes was inhibited with a mean ED50 of 8.4 microg mL(-1) and 24.5 microg mL(-1) for protolichesterinic acid and lobaric acid, respectively. These concentrations are of the same order of magnitude as the IC50 values in the 5-lipoxygenase assay. Significant cell death (assessed by the MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-( 4-sulfophenyl)-2H-tetrazolium) assay and trypan blue exclusion) occurred in the three malignant cell-lines at protolichesterinic acid and lobaric acid concentrations above 20 and 30 microg mL(-1), respectively. In K-562 morphological changes consistent with apoptosis were detected. Up to 38% cell death was observed at 20 microg mL(-1) for protolichesterinic acid and 15 microg mL(-1) for lobaric acid in mitogen-stimulated lymphocytes but unstimulated lymphocytes were clearly less sensitive. In contrast, the DNA synthesis, proliferation and survival of normal skin fibroblasts were not affected at doses up to 20 microg mL(-1) for protolichesterinic acid and 30 microg mL(-1) for lobaric acid. We conclude that the anti-proliferative and cytotoxic effects observed might be related to the 5-lipoxygenase inhibitory activity of protolichesterinic acid and lobaric acid. These results open up the opportunity for future studies of these lichen metabolites with regard to their anti-tumour and anti-inflammatory properties.

4-Butyrolactone↗

PubMed1985

In vitro evaluation of the antimicrobial activity of lichen metabolites as potential preservatives.

Antimicrobial screening of several lichen species and subsequent isolation and structure elucidation of active compounds revealed that the hydrolysis products of certain lichen metabolites, i.e., depsides, were active against gram-negative bacteria and fungi as well as gram-positive bacteria. The active constituents isolated from Stereocaulon alpinum and Peltigera aphthosa were identified, respectively, as methyl beta-orsellinate and a mixture of methyl and ethyl orsellinates. MIC determinations indicated that activity of these compounds was superior to that of the commonly used preservative agents methyl and propyl p-hydroxybenzoates and was of the same order as that of chlorocresol.

Anti-Bacterial Agents↗