Chemical composition and product quality control of turmeric (Curcuma longa L.)

Abstract: Chemical constituents of various tissues of turmeric (Curcuma longa L.) have been extensively investigated. To date, at least 235 compounds, primarily phenolic compounds and terpenoids have been identified from the species, including 22 diarylheptanoids and diarylpentanoids, eight phenylpropene and other phenolic compounds, 68 monoterpenes, 109 sesquiterpenes, five diterpenes, three triterpenoids, four sterols, two alkaloids, and 14 other compounds. Curcuminoids (diarylheptanoids) and essential oils are major bioactive ingredients showing various bioactivities in in vitro and in vivo bioassays. Curcuminoids in turmeric are primarily accumulated in rhizomes. The essential oils from leaves and flowers are usually dominated by monoterpenes while those from roots and rhizomes primarily contained sesquiterpenes. The contents of curcuminoids in turmeric rhizomes vary often with varieties, locations, sources, and cultivation conditions, while there are significant variations in composition of essential oils of turmeric rhizomes with varieties and geographical locations. Further, both curcuminoids and essential oils vary in contents with different extraction methods and are unstable with extraction and storage processes. As a result, the quality of commercial turmeric products can be markedly varied. While curcumin (1), demethoxycurcumin (2), and bisdemethoxycurcumin (5) have been used as marker compounds for the quality control of rhizomes, powders, and extract (“curcumin”) products, Ar-turmerone (99), -turmerone (100), and -turmerone (101) may be used to control the product quality of turmeric oil and oleoresin products. Authentication of turmeric products can be achieved by chromatographic and NMR techniques, DNA markers, with morphological and anatomic data as well as GAP and other information available.