ABSTRACT
The common cold is a viral infection with important economic burdens in Western countries. The research and development of nutritional solutions to reduce the incidence and severity of colds today is a major focus of interest, and larch arabinogalactan seems to be a promising supportive agent. Arabinogalactan has been consumed by humans for thousands of years and is found in a variety of common vegetables as well as in medicinal herbs. The major commercial sources of this long, densely branched, high-molecular-weight polysaccharide are North American larch trees. The aim of this article is to review the immunomodulatory effects of larch arabinogalactan derived from Larix laricina and Larix occidentalis (North American Larix species) and more specifically its role in the resistance to common cold infections. In cell and animal models, larch arabinogalactan is capable of enhancing natural killer cells and macrophages as well as the secretion of pro-inflammatory cytokines. In humans a clinical study demonstrated that larch arabinogalactan increased the body's potential to defend against common cold infection. Larch arabinogalactan decreased the incidence of cold episodes by 23 %. Improvements of serum antigen-specific IgG and IgE response to Streptococcus pneumoniae and tetanus vaccination suggesting a B cell dependent mechanism have been reported in vaccination studies with larch arabinogalactan, while the absence of response following influenza vaccination suggests the involvement of a T cell dependent mechanism. These observations suggest a role for larch arabinogalactan in the improvement of cold infections, although the mode of action remains to be further explored. Different hypotheses can be envisaged as larch arabinogalactan can possibly act indirectly through microbiota-dependent mechanisms and/or have a direct effect on the immune system via the gut-associated lymphoid tissue (GALT).
ABSTRACT
Inflammation plays a major role in many diseases, for instance in arteriosclerosis, rheumatoid arthritis, autoimmune disorders and cancer. Since many plants contain compounds with anti-inflammatory activity, their consumption may be able to prevent the development of inflammatory-based diseases. Edible ferns are some of the most important wild vegetables in China and have traditionally been used both for dietary and therapeutic purposes. In this study we investigated the anti-inflammatory and antioxidant potential of fern extracts from Matteuccia struthiopteris, Osmundajaponica, Matteuccia orientalis and Pteridium aquilinum intended for use as nutraceuticals. Two modes of action were investigated: the inhibition of the pro-inflammatory gene expression of interleukin-1 beta (IL1-ß) and interleukin-6 (IL6), and the gene expression of iNOS by LPS-elicited macrophages. The results showed a decrease of IL1-ß gene expression for the five fern extracts. This effect was more pronounced for the extracts prepared from the roots of O. japonica (IC50 of 17.8 µg/mL) and the young fronds of M orientalis (50.0 µg/mL). Regarding the indirect measurement of NO, via iNOS gene expression, an interesting decrease of 50% was obtained with the extract of M. orientalis fronds at a low concentration (20 µg/mL) compared with P. aquilinum fronds (160 µg/mL) and leaves of O. japonica. The latter showed a higher decrease but at a high concentration of extract (160 µg/mL). The five fern extracts were also evaluated for their ability to scavenge 2,2-diphenyl-l-picrylhydrazyl (DPPH) radicals and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). All fern extracts exhibited antioxidant effects but the roots of O. japonica and the fronds of M orientalis were most efficient. The HPLC-MS analysis of the constituents of the fern extracts confirmed the presence of chlorogenic acid, caffeic acid, p-coumaric acid, ferulic acid, kaempferol and apigenin, molecules known to exhibit antiinflammatory and/or antioxidant properties.