Synthesis of 9,12-dioxo-10(Z)-dodecenoic acid, a new fatty acid metabolite derived from 9-hydroperoxy-10,12-octadecadienoic acid in lentil seed (Lens culinaris Medik.)

The previously unknown linoleic acid peroxidation product 9,12-dioxo-10(Z)-decenoic acid (Z5) was detected in lentil seed flour (Lens culinaris Medik.) by electron impact mass spectrometry (EI-MS) after derivatization with pentafluorobenzyl-hydroxylamine-hydrochloride, methylation of acidic groups with diazomethane, and protection of hydroxylic groups with N-methyl-N-trimethylsilyl-trifluoroacetamide. The structure of the natural product was confirmed by synthesis of Z5, 9,12-dioxo-l0(E)-decenoic acid, and derivatives. EI-MS, nuclear magnetic resonance and gas chromatographic data of these compounds and synthetic intermediates are discussed.

Lignans from the roots of Urtica dioica and their metabolites bind to human sex hormone binding globulin (SHBG).

Polar extracts of the stinging nettle (Urtica dioica L.) roots contain the ligans (+)-neoolivil, (-)-secoisolariciresinol, dehydrodiconiferyl alcohol, isolariciresinol, pinoresinol, and 3,4-divanillyltetrahydrofuran. These compounds were either isolated from Urtica roots, or obtained semisynthetically. Their affinity to human sex hormone binding globulin (SHBG) was tested in an in vitro assay. In addition, the main intestinal transformation products of plant lignans in humans, enterodiol and enterolactone, together with enterofuran were checked for their activity. All lignans except (-)-pinoresinol developed a binding affinity to SHBG in the in vitro assay. The affinity of (-)-3,4-divanillyltetrahydrofuran was outstandingly high. These findings are discussed with respect to potential beneficial effects of plant lignans on benign prostatic hyperplasia (BPH).

Aromatase inhibitors from Urtica dioica roots.

Methanolic extracts of stinging nettle (Urtica dioica L.) roots were investigated for aromatase inhibition. Enzyme inhibition was detected only after appropriate chromatographic separation. Inhibitory effects on aromatase could be demonstrated in vitro for a variety of compounds belonging to different classes. The following compounds developed weak to moderate activity: secoisolariciresinol, oleanolic and ursolic acid, (9Z,11E)-13-hydroxy-9,11-octadecadienoic acid, and 14-octacosanol (5). Inhibitory effects on aromatase have been known to date neither for pentacyclic triterpenes nor for secondary fatty alcohols. The potential physiological significance of the above findings is discussed. Compound 5 is a previously unknown constituent of plants.

Plant constituents interfering with human sex hormone-binding globulin. Evaluation of a test method and its application to Urtica dioica root extracts.

A test system is described, which allows the search for compounds interfering with human sex hormone-binding globulin (SHBG) even in complex plant extracts. The method has been evaluated and applied to Urtica dioica root extracts. The lignan secoisolariciresinol (5) as well as a mixture of isomeric (11 E)-9,10,13-trihydroxy-11-octadecenoic and (10 E)-9,12,13-trihydroxy-10-octadecenoic acids (3 and 4, resp.) were demonstrated to reduce binding activity of human SHBG. Methylation of the mixture of 3 and 4 increased its activity about 10-fold.

The common occurrence of furan fatty acids in plants.

The observation that F-acids (1) occur in rat chow initiated a search for F-acids in human diet. We observed that the amount of F-acids with a pentyl side chain in alpha-position taken up with a one-day diet correlates well with the amount of excreted degradation products, the pentyl urofuran acids (2), (3) and (4). Therefore it can be concluded that F-acids with a pentyl side chain are not produced in the human body but are introduced through the diet. The origin of F-acids carrying an alpha-propyl side chain is less clear. The amount of propyl-urofuran acids (2) and (3) excreted in urine was found in one case out of three to be five times higher than the amount of F-acids carrying a propyl group in alpha-position taken up by the diet. Therefore, it can presently not be excluded that a portion of the propyl F-acids is produced by the body. F-acids found in human food are mainly introduced into the body by vegetables and fruits. F-acids were found also in birch leaves in considerable amounts, as well as in grasses, dandelion and clover leaves. Thus, we can conclude that F-acids are common constituents of plants.

Unusual conjugates in biological profiles originating from consumption of onions and garlic.

After consumption of onions or garlic, biological profiles of human urine samples show, in the methylated conjugate fraction, peaks corresponding to the methylates of N-acetyl-S-(2-carboxypropyl) cysteine (1), N-acetyl-S-allylcysteine (2) and hexahydrohippuric acid (3). The compounds 1 and 2 are metabolites of peptides introduced with onions or garlic into the body.