Phytochemicals are chemical compounds created by plants. They can enhance a plant's color, flavor, and aroma and provide defense systems such as toxins.
Phytochemicals are produced in primary and secondary metabolism of plants. Primary metabolites like sugars and amino acids are used for basic plant survival. As secondary metabolites phytochemicals are specialized.
They aren't directly involved in growth, development, or reproduction. They assist the plant's interaction with its environment. Usually rooted in one place, a plant needs communication and strong defenses.
Environmental stressors include competition from other plants, insect attacks, and exposure to diseases. Phytochemicals act as a defense system, helping plants withstand these threats.
The bright orange of carrots comes from beta-carotene, a carotenoid which converts to vitamin A in a body. Vitamin A is needed by all vertebrate animals. The most influential carrot carotenoid is β-carotene.
In plants and algae carotenoids absorb light energy for photosynthesis, and provide photoprotection. Cattle transform beta carotene from green plants into vitamin A.
During a typical pasture season, their daily intake of carotene exceeds their needs by 3-5 times. A cow has about 4 months' supply of vitamin A in her liver.
The phytochemical resveratrol occurs in red wine and grapes. Resveratrol is a phytoalexin, a protective antibiotic. Plants produce it under stress from factors like fungal attacks, drought, ultraviolet radiation or inflammation.
Phytochemicals influence interactions between plants and pollinators, and attract beneficial insects. Flowers emit volatile organic compounds (VOCs) to tempt pollinators like bees and butterflies.
Alkaloids, a main phytochemical, deter herbivores due to bitterness and toxicity. Amygdalin is a bioactive cyanogenic phytochemical in the kernels of apricots, (bitter) almonds, apples, plums and peaches.
Tobacco plants use nicotine to repel insect pests. Tannins in oak leaves and black tea leaves have bitter, astringent tastes unappetizing to most natural consumers.
Polyphenols in tea include flavonoids, epigallocatechin gallate (EGCG) and other catechins or antioxidants.
Acorns are poisonous to horses, cattle and dogs. People who want to eat acorns must remove the toxins by boiling or cold soaking them multiple times until the water is clear. They will still retain some tannins.
Capsaicin, the fiery compound in chili peppers, deters mammals from eating the fruit, while having little effect on birds who disperse the seeds. The milky sap of milkweed contains cardiac glycosides.
These highly toxic, foul tasting compounds can cause heart failure in some animals like deer. The terrible taste usually repulses a consumer before that happens.
Plants are continually under attack from bacteria, fungi and viruses. Allicin, which produces the pungent aroma of garlic, is an antifungal and antibacterial compound for the plant.
Phytoalexins are produced by many plants including alfalfa, chickpea and soybean in response to fungal or bacterial infection. Natural antibiotics, they are meant to halt the advance of the pathogen in the plant.
Plants also compete with each other for resources like sunlight and nutrients. Some plants release allelopathic chemicals into the soil, inhibiting the growth of nearby competitors.
Violets, which are edible, have an interesting defense. Ionone, the main scented component of the flower, numbs the sense of smell. This tricks the wild consumer into thinking there are no more violets, and going away.
In competitive environments, chicory plants release sesquiterpene lactones to hinder growth of plants around them. Black walnut tree release juglone into the soil, poisoning the ground for a competitive edge.
Conversely, phytochemicals help plants communicate. Release of volatile organic compounds signal danger to nearby plants, triggering defense responses.
Browsed by animals like giraffes, the acacia tree not only turns its leaves bitter but alerts other acacias of the danger. They embitter their leaves before the giraffes arrive.
Not all phytochemicals are defensive. One prominent group is the flavonoids. They create vibrant colors and aromas of flowers to attract pollinators. The bright hues are marigolds come from flavonoids.
Rose fragrance arises from terpenoids, the volatile compounds guiding pollinators to the nectar source. Anthocyanins create the red, blue, and purple hues in fruit and flowers like pansies and purple cauliflower.
Many of the flavonoid compounds are edible by animals. Bright flowers like violets and roses are used in human cuisine. Blueberries and raspberries are beloved by bears and birds.
This helps in seed dispersal. Seeds pass through digestive tracts of animals to sprout in fertile soil, except in the case of humans, who flush them down the toilet.
Agricultural methods significantly influence phytochemical levels in food. Organic farming focuses on enhancing soil health and natural pest control, producing crops like tomatoes with higher phytochemical concentrations.
Furocoumarins are toxins produced mainly by citrus like lime and present in many other plants, like parsley, celery root and parsnip. They're activated by damage to the plant and fungal attacks.
Conversely, many industrial farming practices rely on synthetic chemicals. These can lead to decreased phytochemical content and increased algal bloom toxicity due to nitrogen and phosphorus runoff.
Agencies governing food labeling in Europe and the United States have guidelines to limit or prevent health claims about phytochemicals on food product or nutrition labels.
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