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Chlorogenic Acid

Dateline: 05/24/99

By Alan Bruzel

Do not for a minute believe that plants exist only to satisfy one's appetite. The compounds they manufacture were once, are now, and will ever be for the plant's benefit, not for anyone else's (till genetic engineering do us part). These compounds exist not only to ameliorate plant injuries, but to deter plant pathogens (including fungi) and plant grazers (including us).

One such compound is chlorogenic acid (CA), an ester of caffeic acid and quinic acid. (CA may also be denoted as 3-O-caffeoylquinic acid.) All three of these substances naturally occur in many plants, and their presence there confers some advantage. CA, present in the surface skin of peaches, inhibits the cutin-digesting enzyme of the brown rot fungus, Monilinia fructicola. CA is thus the fruit's first line of defense against fungal invasion.

Caffeic acid	Quinic acid

An enzyme (polyphenol oxidase) present inside many raw fruits and vegetables will convert the surface CA into esthetically unappealing brown colored oxidation products during cutting or peeling. Sulfites added to some prepared foods maintain their "fresh" appearance by preventing this browning reaction, but not all consumers are enamored of sulfite addition to their food.

Chlorogenic acid (CA)

The coffee bean is a repository for many interesting chemicals. Caffeine is present to the extent of four percent (tea leaves also contain four percent caffeine), but CA, at two percent, isn't far behind, and caffeic acid weighs in at 0.2 percent. CA's documented ability to act as an antioxidant (many anti-cancer compounds are antioxidants) must be tempered with the knowledge that CA (and caffeic acid) also act as mutagens (compounds that damage DNA and may possibly induce carcinogenesis). Because of accumulating chemical information regarding the foods we eat, a light supper may well become a desperate act, not recommended for the faint of heart.

Recommended Web resources for additional information:

Coffee and Caffeine FAQs
With additional information on theobromine and theophylline.

Cyclomaltoheptaose (beta-Cyclodextrin) Inclusion Complex Formation with Chlorogenic Acid
Inhibition of CA-mediated browning in fruits and vegetables. Abstract from the Agricultural Research Service, US Department of Agriculture.

Human Exposure/Rodent Potency Index
Mutagenic agents naturally present in foods. Part of the Carcinogenic Potency Project. Publications list available. From the University of California at Berkeley.

Iron Chelation by Chlorogenic Acid as a Natural Antioxidant
CA complexes with iron, preventing iron-induced lipid peroxidation. Abstract from Bioscience, Biotechnology, and Biochemistry.

Mechanism for the Phenolics-Dependent H₂O₂ Scavenging in Vascular Plants
CA's role as an intermediary between hydrogen peroxide and ascorbic acid. From the Australian National University.

Phenolic Compounds
CA and caffeic acid decrease nutty flavor in roasted foods. Article by C.T. Ho in Prepared Foods.

Phenolic Compounds of Buckwheat Herb and Influence of Plant and Agricultural Factors (Fagopyrum esculentum Moench and Fagopyrum tataricum Gärtner)
Quantitation of CA and related compounds in various parts of buckwheat plant. Article from Current Advances in Buckwheat Research.

Plants - Man
Toxic materials present in food plants. From Richard H. Falk, University of California at Davis.

Purification of a Novel Cutinase from Monilinia fructicola Using Trifluoroketone Affinity Chromatography
CA inhibits synthesis of a fungal cutinase. Abstract from the American Phytopathological Society.

Role and Control of Antioxidants in the Tomato Processing Industry
CA and other polyphenols during growth of tomatoes. From the Mediterranean International Association of the Processing Tomato.

Suppression of the N-Nitrosating Reaction by Chlorogenic Acid
Mechanism of CA as an antioxidant. Abstract from Biochemical Journal.

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