Chapter 53: Caffeic Acid

INTRODUCTION

SOURCE

Caffeic acid (3,4-dihydroxycinnamic acid) is found in several grains, fruits, and vegetables.⁵ It also occurs in Coffea arabica (coffee beans), particularly in its esterified form, chlorogenic acid (5-caffeoylquinic acid).^6,7 Some of the best sources of caffeic acid, besides coffee, include grapes, wine, tea, apples and apple juice, cider, blueberries, sunflower seeds, olives, olive oil, argan oil, spinach, cabbage, asparagus, and globe artichoke.^4,8–12 Caffeic acid is one of the main hydroxycinnamic acids (along with ferulic and coumaric), a major class of phenolic compounds that represent the most widely dispersed phenylpropanoids in plants.^6,8 Further, it is one of the primary constituents of Rosmarinus officinalis (rosemary) and Capparis spinosa (caper bush), which have been shown to confer cutaneous benefits.^13,14 Rosemary, in fact, is used often as a spice and is included in beverages, cosmetics, and as a therapeutic herb in traditional medicine.¹³

Caffeic acid has also been isolated in various other plants, including Melissa officinalis (lemon balm), and several species of Echinacea, which are known to exhibit various clinical properties.^15–20 In addition, derivatives of caffeic acid are important components in Plantago major, a plant used broadly in traditional folk medicines.²¹ Caffeic acid phenethyl ester (CAPE), an active constituent of propolis extract, a product of honeybee hives (see Chapter 60, Honey/Propolis/Royal Jelly), specifically inhibits nuclear factor (NF)-κB and is known to display a wide array of biological activity, including antioxidant, anti-inflammatory, antiproliferative, cytostatic, and antineoplastic.²² It has greater lipid solubility and is thought to exert greater anti-inflammatory and antibacterial activity as compared to caffeic acid.^23,24

HISTORY

Cognizance of health benefits derived from caffeic acid dates back at least to 400 BCE, when herbal formulations including caffeic acid were administered to facilitate sleep. It is not known who first discovered caffeic acid. Notably, even though caffeic acid and caffeine are present in coffee, they are unrelated compounds.

CHEMISTRY

Along with other polyphenolic acids such as ferulic, ellagic, and tannic, caffeic acid is thought to have considerable anticarcinogenic potential,²⁵ and is known to confer antioxidant activity (Table 53-1).¹² Like ferulic acid, caffeic acid is also synthesized in the wide variety of plants in which it is found through the shikimate pathway from l-phenylalanine or l-tyrosine (see Chapter 54, Ferulic Acid).^8,26 Caffeic acid is conjugated with saccharides,^5,26 reacts ...