Variability of curcuminoids: Antioxidative components in ethanolic turmeric extract determined by UV and HPLC methods

Abstract

In Thailand, turmeric (Curcuma longa) is mainly used in the forms of capsules/tablets of the powder for herbal medicine while its extract is also used in herbal cosmetics and functional food. Thus the quality assessment of this plant is needed to control the limits of volatile oil and curcuminoids contents. This study was undertaken to evaluate total curcuminoid content in the ethanolic turmeric extract of C. longa rhizome collected from ten locations from the North, Northeast, Central and South of Thailand by a UV spectrophotometry and HPLC. Each curcuminoid content (curcumin, demethoxycurcumin and bisdemethoxycurcumin) determined by HPLC was also reported. By a UV spectrophotometer, the total curcuminoids content of all extracts was found within the limits of 14.14 ± 0.87% to 26.76 ± 0.17% w/w. By HPLC, the contents of curcumin, demethoxycurcumin, bisde-methoxycurcumin and total curcuminoids were found in the range of 8.55 ± 0.42% to 15.88 ± 0.46%, 1.50 ± 0.14% to 4.16 ± 0.17%, 5.54 ± 0.23% to 9.33 ± 0.30%, and 16.93 ± 0.63% to 29.37 ± 0.90% w/w of the extract, respectively. This indicates that the ethanol extract of C. longa should contain not less than 16% w/w total curcuminoids when determined by HPLC and not less than 13% w/w when determined by UV spectrophotometry. The samples from the South where rain is obtained all year were found to contain the highest amount of total and individual curcuminoid. The result confirms that turmeric grown in the South of Thailand is the best source for high contents of individual and total curcuminoids. This information would be a useful database for medicinal plant of the country, to maximize the potential of local community, especially for C. longa which is a "champion product" of Thailand. The results are also useful as a guide for further standardization of turmeric extracts used for pharmaceutical purposes.