Chapter 9 – Garcinoic Acid: A Promising Bioactive Natural Product for Better Understanding the Physiological Functions of Tocopherol Metabolites

Abstract Garcinia kola is traditionally used in African medicine by people who believe that it has purgative, antiparasitic, and antimicrobial properties. The seeds are used for treating bronchitis, throat infections, colic, head or chest colds, cough, and liver disorders, and as a chewing stick. Garcinoic acid ( trans -13′-carboxy-δ-tocotrienol) is an interesting δ-tocotrienol derivative that can be extracted from the seeds of G. kola . Garcinoic acid carries a carboxylic group at the end of the aliphatic side chain and is thus structurally related to α-13′-carboxychromanol (α-13′-COOH), a long-chain metabolite of α-tocopherol that is produced in the liver to allow degradation of the aliphatic side chain by β-oxidation in peroxisomes. The long-chain metabolite α-13′-COOH can be easily synthesized from garcinoic acid by hydrogenation of the double bounds of the aliphatic side chain and subsequent methylation of the chroman ring system, thus making functional studies with the metabolite possible. Recent studies of our group have shown that the long-chain metabolite α-13′-COOH acts as a regulatory metabolite via pathways that are different from its metabolic precursor α-tocopherol. α-13′-COOH acts proapoptotic by inducing oxidative stress but exhibits also interesting antiinflammatory features and effects on cellular lipid metabolism. Future studies will help for better understanding the physiological role of the metabolite and for using garcinoic acid as a lead structure for a putative new class of antiinflammatory drugs.