Carrot, Celery, Fennel, Parsley, Parsnip Cytotoxic Activities

Extracts of roots and bulbs of carrots, celery, fennel, parsley, and parsnip were investigated for their content of polyacetylenes. All five species contained polyacetylenes, although carrots and fennel only in minor amounts.

Carrots, celery, fennel, parsley, and parsnip, are widely cultivated vegetables in temperate regions. Despite their wide usage as foodstuff, little is known about nonpolar secondary metabolites from celery bulbs, fennel bulbs, and parsnip roots.

Polyacetylenes possess a great number of beneficial as well as potential detrimental bioactivities for the human consumer. Polyacetylenes are potent antifungal and antibacterial compounds. They are also known to be inhibitors of a number of enzymes such as diacylglycerol acyltransferase, inducible nitric oxide synthase, and cholesteryl ester transfer protein as well as microsomal and mitochondrial enzymes. In vitro experiments indicate that some polyacetylenes might exhibit antiallergenic and anti-inflammatory activities. In addition, polyacetylenes have proven to be cytotoxic against a number of solid and leukemic cancer cell lines and to potentiate cytotoxicity of other anti-cancer drugs. For example, panaxytriol has been shown to rapidly inhibit cellular respiration in B16 melanoma cells transplanted to mice.

A medicinal usage of pure polyacetylenes is not feasible because of their pronounced chemical instability and their ability to induce allergic reactions. However, consumption of food containing polyacetylenes might have a chemopreventive benefit.

A dose-dependent biphasic effect of falcarinol from carrots on epithelial cells has been demonstrated recently. Low concentrations of falcarinol stimulated growth of these cells; in contrast, higher concentrations had an inhibitory effect. This is in line with the assumption that bioactive secondary metabolites contribute to the beneficial effects of a diet rich in fruits and vegetables against cancer and cardiovascular disease. Bioavailability of falcarinol from carrots in humans was demonstrated recently in biologically relevant concentrations. It was also demonstrated that dietary falcarinol intake inhibited cancerous lesions in mice.

Adverse effects due to an excessive intake of polyacetylenes with the human diet are not to be expected, because polyacetylenes have a bitter off-taste in higher concentrations and are one of the main compounds contributing to the bitter taste of stored carrots.

The present study has investigated the isolation and structure of polyacetylenes from celery, the contents of these compounds in celery and other vegetables from the Apiaceae family, and the in vitro cytotoxicity of four polyacetylenes isolated from celery against different human cancer cell lines.

All investigated polyacetylenes showed medium-level cytotoxicity against the investigated leukemia, lymphoma, and myeloma cell lines.

Consumption of celery, parsley, and parsnip is expected to lead to an uptake of polyacetylenes in quantities where biological effects (e.g., chemopreventive effects) are occurring. The average amount of polyacetylenes contained in umbelliferous vegetables might be subject to considerable variation due to different cultural varieties present and effects of processing and storage on the content of polyacetylenes in these plants.

Another point to be kept in mind is the frequency and amount of vegetables taken in by human consumers. Here carrots play a dominant role. Therefore, polyacetylenes from carrots will contribute the largest amount of polyacetylenes to the human diet, though our investigations indicate that other vegetables from the Apiaceae family may contain higher concentrations of these bioactive food constituents.

The so far unexplained paradox that high contents of natural carotenes in blood correlate with a low incidence of several types of cancer, while carotenes taken as food supplements do not have a positive effect, was linked with the fact that carrots are the major source of carotenes in Europe and North America and that carrots are also the only known major food items that contain the bioactive polyacetylene falcarinol. These authors concluded that the content of polyacetylenes in carrots and facarinol in particular might be responsible for the beneficial effects of carrot consumption. This implies that the observed negative correlation of low cancer risk with high intake of natural carotene is coincidental and produced by the co-occurrence of carotenes and polyacetylenes in carrots. If these findings can be verified, celery, parsley, and parsnip, which contain high amounts of bioactive polyacetylenes, will become promising ingredients of a diet aimed at cancer prevention.

Edited from: Cytotoxic Polyacetylenes from Apiaceae Vegetables J. Agric. Food Chem., Vol. 53, No. 7, 2005 2523