Medicinal properties, lignans

Most of these compounds, e.g. quercetin, possess various degrees of antioxidant or free radical scavenging properties. A number of phenolic compounds have medicinal properties and have long been used as drugs. For example, etoposide and teniposide, two lignans, are anticancer drugs. 

Lignans are colorless, crystalline, solid substances widespread in the plant kingdom (mostly as metabolic intermediaries) and having antioxidant, insecticidal, and medicinal properties. Plants containing lignans with anticancer properties include the following ... 

The resin product obtained by extraction of the dried roots and rhizomes of the North American plant Podophyllum peltatum L. (the American mandrake or mayapple) and of the related Indian species Podophyllum emodi Wall. Ex Royle is known as podophyllin and has long been known to possess medicinal properties. The major active substance in podophyllin is the lignan lactone podophyllotoxin (7) although a variety of other lignans and lignan glycosides have also been isolated from podophyllin. ... 

Medicinal Properties. In terms of medicinal properties, plants containing lignans have been used as folk medicines by many different cultures. For instance, both the North American Indians and the Native of the Himalayas have utilized, for about 400-600 years, alcoholic extracts of Podophyllum rhizomes (rich in the lignan podophyllotoxin 87) as a cathartic and a poison (90),... 

The traditional Chinese herbal medicine Shin-i is highly praised for its antiinflammatory effect [80]. Magnoshinin 164 (Scheme 12.24), isolated from the dry flower buds of Magnolia ulicifolia, has been shown to be the lignan responsible for this interesting biological property [81]. 

A native of the American Southwest, and a traditional medicine of Native Americans, a tea made from the leaves and twigs contains the lignan named nordihydoiguaiaretic acid (NDGA). Considered the active ingredient, it has powerful antioxidant properties. The leaf extract of a South American subspecies was in fact found to inhibit cancer growth. In any event, there are reports of liver damage from its use. Definitive human clinical trials await. 

In order to explain and confirm the biological activities claimed by the traditional medicine, and to search for new biologically active compounds we studied the antimicrobial, antioxidative, immunomodulatory, antiinflammatory, skin-regenerating and antiviral properties of Fraxinus ornus bark extract and its components. In a parallel detailed phytochemical investigation of the extract we isolated and determined the structures of many hydroxycoumarins, secoiridoid glucosides, caffeoyl esters of phenylethanoid glycosides, lignans and other phenolic compounds. 

Oxidative cellular damage by reactive oxygen species such as superoxide anion, hydroperoxy and hyassociated with various human chronic diseases, e.g. cancers, inflammation, arthritis, atherosclerosis and also with the process of ageing. Claims that diet and increased intake of nutrients exhibiting antioxidative activity have a preventative effect on chronic diseases have increased in recent years. In this context, polyphenolic compounds such as tannins, flavonoids, coumarins, lignans and caffeic acid derivatives, which are abundantly contained in a large number of medicinal plants, foods and beverages, are of particular interest for human health care because of the antioxidative properties widely found in plant phenolics. The antioxidative activity of tannins has been extensively studied in various in vitro and in vivo experimental systems and summarized in reviews [96, 97]. Such activity includes the inhibition of lipid peroxidation induced by NADPH-ADP and ascorbic acid-ADP in rat liver microsomes and mitochondria, respectively... 

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