This document summarizes recent research on phytochemicals. It discusses studies that examined the effects of thermal treatments and cooking methods on phytochemical content in berries and vegetables. Other studies investigated the phytochemical profiles and antioxidant activities of black rice, hot peppers, and lettuce grown with abscisic acid. The document concludes that phytochemical content is dependent on many factors and more research is needed to understand actual health benefits.
2. Introduction
In the past twenty years, phytochemicals and their importance in various foods have been
recognized and established (1). More recently, phytochemicals have been the focus of many research
studies, and are now seen on the market as dietary supplements. Each phytochemical found in food
sources plays a different role in the human body. Carotenoids are known to reduce the risk of cancer and
flavonoid molecules are potent antioxidants. Furthermore, anthocyanin compounds, which are found in
berries, help to improve neuronal and cognitive brain functions. In addition, they help with ocular health
and protect DNA integrity. Phytochemicals such as phenolic acids and tannins naturally occur in coffee
and tea, and research has proven they may help in the prevention of chronic and degenerative disorders
(2). The following studies discuss current literature that is published (or in press) in regards to
advancements in phytochemicals. In addition, Table 1 (found on pg. 6) lists phytochemicals, food sources,
and their benefits. Also, see Figure 1 (found on pg. 7) for photomicrgraphed images of two common
phytochemicals.
The factors that influence phytochemical content include: the weather (year-to-year),
environmental conditions from one farm to the next, soil conditions, and farming methods. These
factors affect the nutritional content of crops, which can influence the amount of phytochemicals that
will be in a crop (1).
Sablani and colleagues (3) reviewed the effects of thermal treatments on phytochemicals in
conventionally and organically grown raspberries and blueberries. They measured anthocyanins,
phenolic compounds, and antioxidant activity. The berries were either steam blanched or non-blanched
than placed into cans with sugar syrup. Then both blanched and non-blanched red raspberries and
blueberries were stored in sterilized bottles in the form of processed fruit juice and pureed berries.
Throughout each process any changes in phytochemicals were closely monitored. Prior to blanching,
the berries showed no significant changes in anthocyanin and phenolic contents. The study showed
3. that during canning, anthocyanin decreased and phenolic content and antioxidant activities increased.
Moreover, blanching improved the amount of phytochemicals held in blueberries prior to the
puree/juicing process. The agricultural production system used (i.e organic or conventional) for both
red raspberries and blueberries showed no significant influence on total anthocyanin, phenolic
compounds, and antioxidant activity during each process.
Milbury and colleagues (4) conducted a study of anthocyanins in blueberries because numerous
studies have suggested that phytochemicals found in berries play a role in reversing age related
cognitive impairment. Additionally, they have been know to protect against neurodegenerative
disorders. For an eight week duration, pigs were fed 2% whole freeze-dried, powered blueberry.
Levels of anthocyanins were measured in the brain. Xenobiotic metabolism had taken place and
anthocyanins were removed by the blood which cause a loss of the phytochemicals. The study
concluded that the benefits of the phytochemicals found in berries were beneficial to the body through
gene expression and signal transduction in the human brain, not through direct phytochemical mega-
doses.
Ferruzzi (2) conducted a literature review on the two most commonly consumed beverages in
the world, coffee and tea. Epidemiological data suggests these beverages have provided evidence that
supports its role in preventing chronic and degenerative diseases. Coffee and tea are both rich sources
of bioactive phytochemicals such as: methylxanthines, amino acids, phenolic acids, and polyphenols.
Recent attention is being drawn to the polyphenols and phenolic acids which are abundant in both
coffee and tea. Their reported biological activities that have been shown include antioxidant activities,
stimulation of NO production and vasolidation, regulation of xenobiotic-metabolizing enzymes,
increased fatty acid oxidation and insulin sensitivity, and modulation of glucose absorption and
utilization.
Hayes and colleagues (5) evaluated the effects of selected phytochemicals on quality indices
and sensorial properties of raw and cooked pork stored in different packaging systems. They injected
4. raw and cooked pork with lutein, sesamol, ellagic acid and olive leaf extract and stored the pork patties
aerobically or in modified atmosphere packs for up to twelve days. The results showed that in both
packaging systems, sesamol, ellagic acid, and olive leaf extract exhibited significant lipid antioxidant
activity in raw and cooked pork. In addition, the study suggests these phytochemicals can be added to
raw and cooked pork and may prove to be safe, natural, and functional ingredients for the pork industry
to utilize in the development of novel functional pork products.
Pellegrini and colleagues (6) studied the phytochemical content and total antioxidant content of
fresh or frozen broccoli, Brussel sprouts, and cauliflower during boiling, microwaving, and basket and
oven steaming. The results showed that fresh broccoli, Brussel sprouts, and cauliflower were able to
retain phytochemicals and total antioxidant content better than the frozen broccoli, Brussel sprouts, and
cauliflower during each cooking method. Steaming preserved the phytochemicals in the fresh
vegetables better than microwaving and the basket and oven steaming method in both the fresh and
frozen vegetables.
Hervert-Hernandez and colleagues (7) conducted studies on the bioactive compounds in hot
peppers. The peppers contain an abundance of phytochemicals that contain antioxidant properties. The
study measured the individual antioxidant, carotenoid, and phenolic content of four hot peppers. In
addition, using an in vitro gastrointestinal model, the degree of intestinal bioaccessibility of carotenoids
(with significance in human health), beta-carotene, beta-cryptoxanthin, and zeaxanthin were estimated.
At ripe stage, all four hot peppers had a high content of bioactive compounds that exhibited significant
antioxidant properties, such as polyphenols and carotenoids, which were partly bioaccessible. The
results suggest 50 to 80% of these carotenoids could reach the colon to be potentially fermented or
could remain unavailable.
Agriculture Research on Phytochemicals
Research is also conducted to see if growers can increase the phytochemical content of lettuce
grown in a greenhouse. Li and colleagues (8) studied the effects of exogenous abscisic acid (ABA) on
5. yield, antioxidant capacities, and phytochemical content of red and green loose leaf lettuce. On the 30th
and 39th days after sowing, three concentrations of ABA in water were sprayed on the blocks, on the
46th day the lettuce was harvested. The phenolic compounds in the red and green lettuce included
caffeoyltartaric acid, 5-O-caffeoylquinic acid, dicaffeoyltartaric acid, 3,5-dicaffeoylquinic acid, and
quercetin 3-(6''-malonyl)-glucoside. In addition, cyanidin 3-glucoside, cyanidin 3-(3''-malonoyl)-
glucoside, and cyanidin 3-(6''-malonoyl)-glucoside were seen in the red lettuce. Significant increases
of individual phytochemical content in red lettuce were measured in response to the ABA except for 5-
O-caffeoylquinic acid; whereas no significant change was observed in the green lettuce. Significant
increases in antioxidant content were observed in both types of lettuce.
Xu and colleagues (9) measured the nutritional and functional properties of immature corn
grains, which are being used as a popular snack/vegetable. In the study, plants at multiple stages were
examined to see if any changes occurred in nutrients, phytochemicals, and antioxidant activity in corn
grains during different stages of growth. The results of the study revealed that during the growth
period of corn grains, phytochemicals and antioxidant levels both decreased.
Current research conducted by Zhang and colleagues (10) studied the phenolic profiles and
antioxidant activity of black rice bran of differenct commercially available varieties. The objective of
the study was to determine the phytochemical profiles and antioxidant activities from twelve varites of
black rice in comparison to white rice. The results of the comparison showed the average values of
free, bound, and total antioxidant activty of black rice was significantlly higher than that of white rice
bran. In addition, all tweleve varities of black rice had higher content of total phenolics, total
flavonoids, and total anthocyans (specifically cyanidin-3-glucoside, cyanidin-3-rutinoside, and
peonidin-3-glucoside) when compared to white rice. The study suggest that knowing the
phytochemical profile and antioxidant activity of black rice bran gives insights to its potential
application to promote health.
6. Conclusion
In conclusion, the phytochemical content of foods is dependent on many variables including
crop conditions, packaging systems used, cooking methods, etc. Phytochemicals are not essential
nutrients; however when consumed, they can help in the prevention of chronic and degenerative
diseases. The future of phytochemicals is in educating consumers on actual health benefits.
Additionally, further research needs to be conducted specifically in regards to actual health benefits, not
just assumed benefits.
Table 1. Phytochemicals, food sources, and benefits ( from reference 11).
Phytochemical Name Food Source Benefits
Allicin Garlic or onions May lower serum cholesterol and
and protect against
cardiovascular disease.
Capsaicin Hot peppers May reduce blood clotting.
Carotenoids Carrots, sweet potatoes, spinach, May have anti-cancer benefits.
kale, etc.
Flavinoids Blueberries, black raspberries, May help to improve memory.
and cranberries
Indoles Cruciferous vegetables Appear to block carcinogens
from damaging DNA.
Isothiocyanates Cruciferous vegetables Inhibit enzymes that promote
cancer activity.
Lignans Whole grains and some seeds May help prevent cancers that
(flax seeds) are estrogen positive from
spreading or metastasizing.
Limonene Citrus fruits May inhibit cancer growth.
Lycopene Tomatoes, pink grapefuit, May retard the growth of
watermelon, guava, and papaya cancers, particularly prostate
cancer.
Phenolic Acids Coffee and fruits May promote excretion of
carcinogens.
Phytic Acid Whole grain May inhibit free radical activity.
Phytosterols Soybeans May slow rate of some cancers.
Resveratrol Grapes, peanuts, and red wine. Inhibits cell growth and lowers
risk of blood clotting.
7. Saponions Legumes and vegetables May slow DNA replication
which affects growth rate of
cancer cells.
Tannins Tea, wine, and legumes Can inhibit cancer activity.
Vitamin C Vegetables and fruit May help lower the risk of oral,
throat, larynx, and esophageal
cancer.
Figure 1. Photomicrographs of common phytochemicals ( from reference 12).
Capsaicin
Phenethyl Isothiocyanate ( A Phenolic Acid)
8. References:
1. Crinnion W. Organic foods contain higher levels of certain nutrients, lower levels of pesticides, and
may provide health benefits for the consumer. Altern Med Rev. 2010;15(1):4-12.
2. Ferruzzi M. The influence of beverage composition on delivery of phenolic compounds from coffee
and tea. Physiol Behav. 2010;100(1):33-41.
3. Sablani S., Andrews P., Davies N., Walters T., Saez H., Syamaladevi R., Mohekar P. Effect of
thermal treatments on phytochemicals in conventionally and organically grown berries. J Sci Food
Agric. 2010;90(5):769-78.
4. Milbury P., Kalt W. Xenobiotic metabolism and berry flavonoid transport across the blood-brain
barrier. J Agric Food Chem. 2010;58(7):3950-6.
5. Hayes J., Stepanyan V., O'Grady M., Allen P., Kerry J. Evaluation of the effects of selected
phytochemicals on quality indices and sensorial properties of raw and cooked pork stored in different
packaging systems. Meat Sci. 2010;85(2):289-96.
6. Pellegrini N., Chiavaro E., Gardana C., Mazzeo T., Contino D., Gallo M., Riso P., Fogliano V.,
Porrini M. Effect of different cooking methods on color, phytochemical concentration, and antioxidant
capacity of raw and frozen brassica vegetables. J Agric Food Chem. 2010;58(7):4310-21.
7. Hervert-Hernandez D., Sayago-Ayerdi S., Goni I. Bioactive compounds of four hot pepper varieties
(Capsicum annuum L.), antioxidant capacity, and intestinal bioaccessibility. J Agric Food Chem.
2010;58(6):3399-406
8. Li Z., Zhao X., Sandhu A., Gu L. Effects of Exogenous Abscisic Acid on Yield, Antioxidant
Capacities, and Phytochemical Contents of Greenhouse Grown Lettuces. J Agric Food Chem. 2010; In
press.
9. Xu J., Hu Q., Wang X., Luo J., Liu Y., Tian C. Changes in the main nutrients, phytochemicals, and
antioxidant activity in yellow corn grain during maturation. J Agric Food Chem. 2010;58(9):5751-6.
9. 10. Zhang M., Zhang R., Zhang F., Liu R. Phenolic Profiles and Antioxidant Activity of Black Rice
Bran of Different Commercially Available Varieties. J Agric Food Chem. 2010; In press.
11. Phytochemicals and Functional Foods. The Bellevue College Website.
http://scidiv.bellevuecollege.edu/rkr/Biology130/lectures/pdfs/Phytochemicals130.pdf . Published April
1999 and October 2003. Accessed June 6, 2010.
12. Davidson M. The Phytochemical Collection. The Florida State University Website.
http://micro.magnet.fsu.edu/micro/gallery/phytochemicals/phytochemical.html . Published September
19, 1995. Updated March 8, 2004. Accessed Jun 6, 2010.
