HerbalEGram: Volume 14, Issue 5, May 2017
Editor’s Note: Each month, HerbalEGram highlights a conventional food and briefly explores its history, traditional uses, nutritional profile, and modern medicinal research. We also feature a nutritious recipe for an easy-to-prepare dish with each article to encourage readers to experience the extensive benefits of these whole foods. With this series, we hope our readers will gain a new appreciation for the foods they see at the supermarket and frequently include in their diets.
The basic materials for this series were compiled by dietetic interns from Texas State University (TSU) in San Marcos and the University of Texas at Austin (UT) through the American Botanical Council’s (ABC’s) Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Perez, ABC Special Projects Director Gayle Engels, and ABC Chief Science Officer Stefan Gafner, PhD, for their contributions to this project.
By Hannah Baumana and Monica Silvab
a HerbalGram Associate Editor
b ABC Dietetics Intern (TSU, 2017)
The caper (Capparis spinosa, Capparaceae) bush is a small, salt-tolerant shrub with trailing, thorny branches and thick, fleshy leaves. Caper has a deep root system and trailing vines that grow seven to 10 feet tall.1 The semi-prostrate branches have ovate, petiolate leaves arranged opposite of each other. The flowers are pink or white with three petals and numerous stamens. Caper is a deciduous, dicotyledonous plant that produces distinctive flower buds, which have a life span of 24 to 36 hours after opening.1,2
Caper’s edible shoots are considered a vegetable, and its processed buds are considered a culinary herb.1The tender shoots emerge in the spring, while the flower buds are harvested from mid-May to mid-August. Each plant produces hundreds of flowers each season. When pickled in vinegar or brine, the immature flower buds form capric acid, which is responsible for caper’s unique, salty-sour flavor.2,3 Once the flower blooms and is pollinated, it produces a fruit two to three inches in length and one-half to three-quarters of an inch in diameter. Caper fruits start out green, but turn purple when ripe. Each fruit contains 200 to 300 seeds.1 The fruit of the caper bush is also harvested, but not commonly used.2
Currently, capers are cultivated commercially in northern Africa, Spain, and Italy. Caper plants in Cyprus, Greece, and Turkey are grown for domestic use and not for export. The United States imports more than $20 million of processed capers annually.1 Caper plants that are two to three years old produce about two pounds of buds in a year, while plants older than four years may produce more than 20 pounds of buds annually.1
Phytochemicals and Constituents
Macronutrients are found in capers in very small amounts. One tablespoon (8.6 grams) of pickled capers has two calories, half a gram of carbohydrates, and minute amounts of protein and fat. An important micronutrient to consider when eating capers is sodium. One tablespoon of capers contains 202 milligrams of sodium, which is 8.5% of the recommended daily intake for a healthy adult.4,5 The flower bud also contains trace amounts of vitamins C and E. The concentration of vitamins can vary from plant to plant. The vitamin C content in capers cultivated in different regions in Tunisia, for example, ranged from 0.3 to 0.5 milligrams per 100 grams of capers.6
A number of bioactive compounds have been isolated from the flower buds of the caper bush. The pickling process has varying effects on the bioavailability of compounds due to different fermentation methods.7 Among the most investigated of these phytochemicals are flavonoids and antioxidants.
Flavonoids from capers reportedly have cytotoxic, anti-inflammatory, antidiabetic, and antiparasitic properties.7,8 Rutin (quercetin-3-O-rutinoside) is the most abundant flavonoid in fresh and pickled caper buds.7 Simple water extractions high in rutin have been shown to reduce inflammation and arrest cell growth in cancer cells, as well as kill intestinal parasites in animals.8,9 Caper flower buds also contain quercetin-3-O-rhamnosylrutinoside, a derivative of quercetin.6
Quercetin, another well-studied flavonoid, is formed from rutin during the pickling process.7 Quercetin can inhibit inflammation and cancer cell growth in the same way as rutin.9 Quercetin has also shown immune-health benefits. Kaempferol 3-O-rhamnosylrutinoside, another flavonoid identified in an aqueous extract, has proven antiparasitic properties.8
The flower bud of the caper bush also contains antioxidants such as carotenoids, tocopherols, ascorbic acid, and a newly identified antioxidant, cappariside, a small organic acid.6,10 Antioxidants eliminate free radicals that cause damage to body tissues and DNA, and have been implicated in the prevention of cancer, kidney damage, and heart disease, as well as protection against prescription drug-induced toxicity.11 The antioxidant effects of flower bud preparations have been shown to be more potent than those of the antioxidants in isolation.8
Historical and Commercial Uses
The unopened flower buds of the caper bush are commercially known as capers.2 Capers are used as a condiment in salads and sauces, or with meat or fish. They are also used in cosmetics and medicines.
Archeological evidence for the historical use of capers as a food and medicine exists among many ancient cultures.12 The earliest known evidence of caper consumption was found in the Mesolithic soil layer of an excavation site in Syria, potentially dating back to 9000 BCE. Nearby ancient peoples may have been using capers in 7500 BCE as evidenced by mineralized seeds found in the Franchthi cave, a Stone Age cave in the Greek Peloponnesian peninsula. Dried seeds found in the Nahal Hemar cave in Israel may have been used as early as 6000 BCE. In China, fresh clumps of capers and plant parts were preserved in entombed containers that are almost 3,000 years old. There is also evidence of Egyptian consumption of capers from 275 BCE to 600 CE.
Historical medicinal uses of capers ranged from expelling bad odor spirits in ancient Arabic cultures to treating paralysis in ancient Xinjiang, China.12 In addition to the buds, the root bark, fruit, and aerial parts of the caper bush were used in traditional remedies. Countries in the native range of caper, including Iran, Iraq, and Syria, used every part of the caper bush for a variety of ailments. As the cultivation and use of capers spread, the Greeks, Egyptians, and Chinese incorporated the caper bush into their traditional medicine practices.
Capers contain phytochemicals that can inhibit inflammation, which supports caper’s usages as a cleanser and pain reliever.9,12 In ancient Chinese, Greek, and Arabic cultures, the root bark was mixed with vinegar or honey and applied topically to treat skin conditions such as ulcers and white spots associated with vitiligo.12 Similarly, the root was consumed as a treatment for inflammation and lacerations of the mouth, spleen, stomach, and intestines. In ancient Egypt, the root was used to reduce the pain of a scorpion sting.
In ancient Greece and China, the caper bush was regarded for its drying properties and was used as an expectorant in treating wet cough and asthma.12 Ancient Romans boiled caper root and root bark in oil and used it as an anthelmintic (digestive tract parasitic worm expeller). Likewise, in the 12th century, the Egyptians used the root to cleanse and dry the stomach.
Current medicinal usages are a testament to caper’s efficacy for treating different ailments. In the Middle East, indigenous groups still use capers as a so-called “blood purifier” and diuretic, to relieve stomach discomfort, treat kidney stones, improve liver function, and treat eczema.13 In Ayurveda, one of the traditional medicine systems of India, caper is used to treat paralysis and tremors, as well as edema, gout, and rheumatism.14 The root bark is still used to stimulate the menstrual cycle, as an expectorant, and to treat paralysis, rheumatism, spleen conditions, and toothaches.15
Commercial capers are not frequently studied for their medicinal properties. However, some research has been conducted on the bioactive compounds in the flower buds.
A recent study investigated the antiparasitic effect of a caper bud extract against Haemonchus contortus, a common parasite in cows and sheep. The large number of eggs and short life span of H. contortus allows the parasite to adapt quickly to its environment.16 Parasite infestations can result in large economic losses in the animal production industry, and current treatments include chemotherapy and vaccinations, which pose a safety concern.17 Researchers compared the caper extract to a commonly prescribed antiparasitic drug albendazole. The flower bud extract (50 mg/mL) was almost twice as effective as albendazole (1 mg/mL) at killing parasites in sheep and inhibited the hatching of parasitic eggs more than the leaf extract.8
The caper bud has also been studied for its anti-inflammatory and cytotoxic properties. A recent study investigated the potential of capers to inhibit nuclear factor-kappa B (NF-κB), a transcription factor that controls inflammation and cell growth. Mutations that impact its activation may lead to uncontrolled cell growth, one of the conditions that can cause a proliferation of cancer cells.18 For this reason, NF-κB is a therapeutic target for pancreatic, renal, and thyroid cancer treatments.18-20 In one in vitro study, researchers tested an aqueous extract of the flower bud and leaves, which were selected for their high levels of phenolic compounds, on human adenocarcinoma cells. The caper extract successfully inhibited the inflammation mechanism, and arrested cell growth in a dose-dependent manner.9
Additionally, a caper flower bud extract has been studied for its ability to treat liver toxicity in animals. Rats were exposed to two different liver toxins: carbon tetrachloride, a known carcinogen that has been used as a commercial refrigerant, propellant, and solvent; and paracetamol, also known as acetaminophen, a pain-relieving drug that can induce liver failure in sufficiently high doses.21 Compared to control, the caper extract resulted in a significant reductions in carbon tetrachloride-induced and paracetamol-induced liver toxicity.
Macronutrient Profile: (Per 1 tablespoon pickled capers, drained)
0.2 g protein
0.4 g carbohydrate
0.1 g fat
Secondary Metabolites: (Per 1 tablespoon pickled capers, drained)
Provides small amounts of:
Vitamin K: 2.1 mcg (2.6% DV)
Dietary Fiber: 0.3 g (1.2% DV)
Provides trace amounts of:
Magnesium: 3 mg (0.8% DV)
Vitamin C: 0.4 mg (0.7% DV)
Iron: 0.1 mg (0.6% DV)
Riboflavin: 0.01 mg (0.6% DV)
Folate: 2 mcg (0.5% DV)
Vitamin E: 0.1 mg (0.5% DV)
Manganese: 0.007 mg (0.4% DV)
Calcium: 3 mg (0.3% DV)
Niacin: 0.06 mg (0.3% DV)
Vitamin A: 12 IU (0.2% DV)
Phosphorus: 1 mg (0.1% DV)
Potassium: 3 mg (0.1% DV)
Thiamin: 0.002 mg (0.1% DV)
Vitamin B6: 0.002 mg (0.1% DV)
DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet.
Recipe: Lemon Capellini with Capers
Adapted from Ina Garten22