Chemical Defenses in Herbs and Spices

Tracking biosynthetic pathways

for human health David Gang By Susan McGinley David Gang holds fresh ginger rhizomes that contain active anti- inflammatory compounds called gingerol and shogaol.

he sweet basil that tops your spaghetti sauce, the ginger warfare: antibacterial, antifungal, antimicrobial,” he says. “They blended into your pumpkin pie, and the turmeric can also deter animal and insect feeding.” Plants create defensive mixed in your potato curry add more than just taste. All compounds by synthesizing them along specialized pathways that Tthree of these culinary flavorings contain powerful compounds— are still not fully understood. Gang wants to find out how these eugenol, gingerol and cucurmin, respectively—that can fight pathways work, and how that process is controlled in plants that certain types of inflammation, infection and other threats to have been a part of ancient cuisines and traditional medicines. human health. People have used these and other herbs and spices “Many of the herbs and spices used in cooking were originally for thousands of years, not only to flavor and preserve their food, used to preserve food, and were quite valuable,” Gang notes. but also as medicine (see sidebar). “Columbus set sail for southeast Asia in search of cloves, Of more immediate interest to the plants that produce these cinnamon and black pepper, which were worth a lot of money. substances is their own survival. They create compounds called Those spices produce a lot of antimicrobial compounds, plus phenylpropanoids that include not only eugenol, gingerol and they preserve meat and keep you from getting sick. But in cucurmin, but also hundreds of others, to defend themselves my lab we’re not medical doctors. We’re really interested in against animals and microorganisms like bacteria and fungi. understanding how the plants actually make these compounds.” Scientists at the University of Arizona are studying the chemical Several federal institutions are also interested in the results. properties of herbs and spices to find out not only how these Funding for this research comes from the National Science protective compounds work, but also how and where they are Foundation for ginger and turmeric, and from the National synthesized in plants. Science Foundation and the USDA for basil. “I’m very interested in how plants interact with the Intrigued by such a vast, unexplored field, Gang began environment, and how they do that chemically,” says David Gang, postdoctoral work in 1999 on eugenol biosythesis in sweet basil a professor in the University of Arizona’s College of Agriculture with Eran Pichersky, a professor at the University of Michigan. and Life Sciences, and a member of the UA’s BIO5 Institute. Gang Gang has continued this collaborative research at the UA not has studied the formation of phenylpropanoids in plants like only with Pichersky, but also with other scientists from the UA, sweet basil, ginger and turmeric for more than a decade. Washington State University, Purdue University, the Salk Institute “How is it that plants are able to defend themselves without for Biological Studies in California, and the Max Planck Institute being able to get up and run away? They do that with chemical in Germany. Gang has several graduate and undergraduate

16 The University of Arizona College of Agriculture and Life Sciences students, as well as post-doctoral fellows underground stem of these plants called working on these projects in his lab. the rhizome, are not as easy to figure Although several different plants make out. Research results will take more time eugenol, the researchers needed one that not only because the plants are more could be grown easily and studied live complex, but also because they just take in Tucson. Cloves, which produce the longer to grow. most eugenol, were eliminated because a “In ginger and turmeric we’re still at the clove tree takes 20 years to make cloves. stage of figuring out how the medicinal

David Gang Instead, sweet basil (Ocimum basilicum) compounds are formed,” Gang admits. Turmeric inflorescence (left). Turmeric extracts contain was chosen because it contains a fair “We do know that just a couple of steps cucurmin, a compound that has powerful antioxidant, amount of eugenol and thrives in hot are needed to produce curcurmin from anticarcinogenic and anti-inflammatory properties. climates. It originated in the Middle common building blocks in all plant East where it still grows wild. Gang cells.” and his team planted basil in a rooftop All of this research is aimed at finding greenhouse on the UA campus and ways to engineer plants metabolically to Active Compounds in harvested leaf samples to study in the make compounds for food, health, energy laboratory. and industry, according to Gang—the Basil, Turmeric and Ginger It turns out that microscopic “dots” on building blocks for interesting products. The following compounds are responsible the surface of basil leaves are actually tiny “We have pretty good means for for the characteristic flavor of the herbs and factories that produce eugenol. engineering the plant to make different oil spices that contain them. Here are just a few profiles, such as in corn and soybeans,” of their healing properties: he says. “But, how can we make plants • Eugenol is the active ingredient in sweet Cloves, which produce better at making feedstocks for fuel basil, cloves, cinnamon and nutmeg. It the most eugenol, were or other industrial applications? I’m serves as an antioxidant in food, fights interested in being able to utilize plants inflammation, and also has analgesic, eliminated because a clove to make products that we as humans antiseptic and anesthetic applications in think are interesting—perfumes, plastics, dentistry. Tulsi, or Holy Basil, which contains tree takes 20 years to eugenol, has been used as the principal make cloves. medicines, flavors, and so on. herb in Ayurvedic medicine for centuries. “Instead of using a chemical factory • Cucurmin is the active ingredient in that could emit pollution, we could do turmeric that gives many dishes in Indian “We’ve been isolating the tissue where it in a living plant, and basil helps us cuisine their traditional golden orange color. these compounds are made, in a special understand how that could be done. We Turmeric has been used in India for more structure on the leaf called a glandular know enough now to know we still need than 5,000 years. Hundreds of studies show trichome,” Gang says. “We’ve been able to to know more. Basil is a good model for that cucurmin has powerful antioxidant, remove the trichomes from the leaf and understanding how metabolic pathways anticarcinogenic, and anti-inflammatory separate them into fractions that produce operate inside a single cell.” Ã properties. It holds promise for treating the compounds. We sequence their arthritis, halting tumor growth, reversing RNA to get an idea of the genes that are some of the effects of cystic fibrosis, and expressed in the trichomes and involved inhibiting HIV reproduction in the body, in the biosynthesis of the compounds. among other uses. This is creative, translational biochemistry, • Gingerol and shogaol, the pungent active with a genomics approach.” The team also compounds in ginger, are highly effective against nausea, including motion sickness determines which enzymes the trichome and morning sickness in pregnancy. Ginger produces, and in turn, which compounds originated in Southeast Asia, where it has result. been used for more than 2,000 years as an “We’ve identified all of the genes anti-inflammatory agent to treat headaches, involved in making eugenol,” Gang says. stomach ailments, joint pain, and other Results of this research were announced problems. in June, 2006. “Now we can take those glandular Note: The herbs and spices mentioned above trichomes, isolate them from other also contain other active compounds. types of cells and use them as a model to study metabolic pathway systems in living organisms. These are the best Contact systems to work with for doing that, in

my opinion. The basil system is good for Brenda Jackson David Gang understanding the basics.” Sweet basil grown in a UA greenhouse yields leaves 520-621-7154 The active ingredients in ginger and [email protected] high in eugenol, a compound with analgesic, antioxidant, turmeric, which accumulate in the anti-inflammatory and anesthetic applications.

2006 Agricultural Experiment Station Research Report 17