|Title||Novel, Natural Sources of Antioxidants and Cell Redox Regulation|
Novel, Natural Sources of Antioxidants and Cell Redox Regulation
Last updated July 29, 1997
Oxidative stress has been implicated in various degenerative diseases, including cancer, atherosclerosis, Alzheimer’s disease, Parkinson disease, diabetes etc. Although each of these diseases has a distinctive feature, free-radicals such as reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been recognized to play an important role in the pathogenesis. Epidemiological evidence suggests that the consumption of fruit and vegetables is negatively associated with the incidence of degenerative diseases. Fruit and vegetables, together with plant derived beverages (tea, wine etc.), are good sources of Antioxidants, vitamins and minerals which are necessary for human health. Besides the action of these well-known nutrients, other components of plants such as polyphenols and polyphenol derivatives may have beneficial effects owing either to their antioxidant properties and their ability to act as modulators of different metabolic pathways.
Many polyphenols containing phytochemicals which have been utilized in the past as the only possible remedy for various diseases. These traditional medicines are now still widely used in the affluent countries, both as an alternative and as a complement to the conventional therapy.
Recently, much attention has been paid to the antioxidant property of flavonoids because of their ability to scavenge ROS or RNS. Many polyphenols have already been reported by our lab and by others to be potent scavengers of both ROS and RNS and therefore may participate in the antioxidant network of the cell. Besides this scavenging effect, many polyphenols may affect the activity of different enzymes which play key roles in the signal transduction and cell activation processes in the immune system. In fact, some flavonoids have been reported to inhibit the activities of different enzymes, including protein kinase C, cyclo-oxygenase, lipoxygenase, myeloperoxidase. Therefore these findings on the effects of flavonoids encourage us to investigate further the beneficial properties of flavonoids.
Our laboratory has been focusing on the biological activity of different plant extracts such as, Gingko biloba (EGb 761), pine bark (Pycnogeriol), and fermented products of Carica papaya (Bio-Normalizer,) as well as some purified flavonoids such as catechin, epicatechin and others.
DESCRIPTION OF RESULTS
1) Antioxidant Activity
The antioxidant activity of plant extracts was assayed by ESR techniques utilizing a new highly sensitive electron spin resonance spectrometer system developed by JEOL (JES-FR30).This instrument has been used in conjunction with analytical regents designed to assess hydroxyl radical, The computerized software in this system computes the level of radical scavenging activity of the samples after normalization of the signals using external manganese dioxide paramagnetic signals. Using this EPR instrument, the scavenging activity of Gingko Biloba extract (Egb 761), of Pycnogenol, and other flavonoids has been tested.
2) Modulation of NO Metabolism
The extract of Gingko biloba (EGb 761) and pine bark extract (Pycnogenol) have been demonstrated to modulate the metabolism of nitric oxide (nitrogen monoxide, NO) in macrophages activated by the bacterial endotoxin lipopolysaccharide and by interferon-g. When activated, macrophages are triggered to express the inducible form of the enzyme nitric oxide synthase (iNOS) and generate massive amounts of NO that change the cell functions indiscriminately. Such a flow of a potentially oxidant species may become harmful for the macrophage itself and for the surrounding tissues. This condition has been indeed recognized in chronic inflammatory diseases. The preincubation of macrophages with EGb 761 and with Pycnogenol, results in a reduction of the production of NO due to the inhibitory effect on iNOS activity and the inhibitory effect on the expression of the mRNA for the iNOS gene.
The results obtained with the fermented product of Carica Papaya which is called Bio-Normalizer is somehow different. Bio-normalizer can up-regulate interferon-g-induced NO production in macrophages, suggesting Bio-Normalizer has an immune-modulating ability.
Taken together, these results suggest that plant extracts may have beneficial effects in pathologies related to oxidative stress and in inflammatory conditions which are accompanied by the expression of iNOS in various cells and tissues.
3) Modulation of the Apoptotic Response. In Activated Macrophages
The overproduction of NO from activated macrophages may potentially become autodistructive since high levels of oxidants can induce both apoptotic and necrotic cell death. Preliminary studies suggest that some plant extracts (Pycnogenol) can modulate the apoptotic response of rat macrophages exposed to NO overflow.
Kobuchi H; Droy- Lefaix MT; Christen Y; Packer L. Ginkgo bi loba extract (EGb 761): inhibitory effect on nitric oxide production in the macrophage cell line RAW 264. 7. Biochemical Pharmacology. 53:897-903 (1997).
Kobuchi H. and L. Packer Bio-Normalizer Modulates Interferon-g-induced Nitric Oxide Production in the Mouse Macrophage Cell Line RAW 264.7 Biochemistry and Molecular Biology International. (1997) in press
Virgili F, Kobuchi H. Packer L. Nitrogen Monoxide (NO) metabolism: anti-oxidant properties and modulation: of inducible NO synthase activity in activated macrophages by procyanidins in: Flavonoids in Health and Disease, L Packer and C. Rice-Evans Eds, M. Dekker, N.Y. 1997 (in press)
Noda, Y. Anza i, K., Kohno, M., Shimmei, M., Mori, A. and Packer, L. Estimation of antioxidant scavenging activity of natural source antioxidants using the computerized JES-FR30 systems. Biochemistry and Molecular Biology International 42: 35-44 (1997).
Noda, Y., Anza i, K., Kohno; M., Shinmei, M., Mori, A. and Packer, L. Estimation of antioxidant scavenging activity of natural source antioxidant using the computerized JES-FR30 system. International Society for Free Radical Research, VIII Biennial Meeting, Barcelona, Spain, Abstract: pp.76-77 (1996)
The Scientist of Novel and Natural Antioxidant
• Dr. Chandan K. Sen, Staff Scientist
• Dr. Hirotsugu Kobuchi, Post-doctoral researcher
• Dr. Fabio Virgil, Post-doctoral researcher
• Dr. Sashwati Roy, Assistant Research Biochemist
• Dr. Yasuko Noda, Post-doctoral researcher
• Dr. Akitane Mori, Professor Emeritus