Phytonutrients (phytochemicals) are plant chemicals, which protect the plants against insects, bacteria, fungi and UV radiation. The phytonutrients give colour, peculiar smell and taste to the different parts of the plants such as the fruits (dried or fresh), the leaves, the stem, tubers, flowers etc. With these, the plants are able to destroy or keep attackers at bay.
These phytonutrients, apart from such benefits to the plants, have been shown scientifically to benefit human beings, health-wise. In their activities in the body they function either as antioxidants, anti-inflammatory agents or immune system boosters. They also act as detoxifiers of foreign substances, especially in the liver where they support a healthy liver.
Common groups of phytonutrients include carotenoids, flavonoids, glucosinolates, sulforazones, phenols, ellargic acid, resveratrol, phytoestrogen, catechin in tea etc. We have already looked at the carotenoids and flavonoids.
These make up a family of about 120 compounds securely stored in the cells of the plants. In this way, they are kept away from the enzyme, myrosinase which catalyses the hydrolytic reaction that breaks glucosinolates down to several bioactive products.
Myrosinase is only released when the plant is cut, cooked or chewed and the products that are produced as it acts on glucosinolates include isothiocyanates, oxazolidine-2-thione, nitriles, thiocyanate ions and indole products.
Glucosinolates are sulfur-containing compounds, which have a pungent aroma and a spicey taste. This pungent aroma comes from mustard oils released from glucosinolates when myrosinase acts upon it. In other words, when the plant is intact, you may not perceive the pungent aroma, until it is cut or chewed. They are predominantly found in cruciferous vegetables of the family, Brassicaceae. They include Brussels sprouts, broccoli, cabbage, cauliflower and Chinese cabbage. Others are horse radish, mustard seed, rapeweed and water cress.
Apart from glucosinolates, cruciferous vegetables also contain vitamins such as folate and vitamin C. There are such minerals as potassium and selenium. A lot of other phytonutrients abound in cruciferous vegetables. There are carotenoids, flavonoids, isothiocyanates, indole-3-carbinol, chlorophyll, lignans, phytosterols and fibre.
Health benefits of glucosinolates
Several research works have been carried out and ongoing, on glucosinolates and its secondary bioactive products. This is more so in the area of cancer.
So far, the following have been found out:
Firstly, the hydrolysis products of glucosinolates can help prevent cancer by eliminating carcinogens before they do damage to DNA.
Furthermore, some of these hydrolysis products may inhibit the activity or metabolism of such hormones as eostrogen that support the development of hormone-sensitive cancers; breast and endometrial cancers are examples.
It has also been found that these hydrolysis products alter cell-signalling pathways. By so doing they prevent mutation, the transformation of normal cells to cancerous ones. Benzylisothiocyanate and thiocyanate have been found to inhibit tumour growth in animals exposed to carcinogens. Colo-rectal cancers have been more susceptible to the effects of these phytonutrients.
Apart from the research works on cancer and glucosinolate-hydrolysis products, there are discoveries in other areas. They show forth antioxidant properties by their ability toeliminate reactive oxygen species and protect the body against oxidative stress damage. This activity may also be the connection between these vegetables and protection against cancer.
Glucosinolates and their hydrolysis products also affect the two-phased detoxification enzyme systems of the liver differently. On one hand, they inhibit the phase i enzyme activities, while inducing the phase ii enzymes which prepare harmful substances for elimination. Also, they induce the liver function that detoxify carcinogens. Glucosinolates generally enhance the detoxification functions of the liver and help to maintain the health of the liver.
On the negative and down side, these glucosinolates and their hydrolysis products have been discovered to have goitrogenic and anti-thyroid activities. Fortunately, an individual has to consume a lot of the vegetables to experience the negative side of glucosinolates
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