Variation of curcuminoids and free radical scavenging activity of rhizome extracts of Curcuma longa in Thailand

The rhizome of Curcuma longa L. or turmeric is a popular herbal drug of Thailand and is used as a coloring agent, household medicine and spice. Medicinal uses of the rhizome are based on the volatile oil which has carminative and antifungal activity [1] and yellow curcuminoids which have anti-oxidative and anti-inflammatory properties [2]. At present, the extract of turmeric is used in herbal cosmetics as natural colorant and additive, and also in drug preparations. So, it is necessary to develop analytical methods for quality assessment of C. longa extracts. TLC-densitometric and HPLC methods were used for quantitative analysis of major antioxidant components; curcumin, demethoxycurcumin, and bisdemethoxycurcumin, in 10 ethanolic extracts of C. longa cultivated in several parts of Thailand. The contents of curcumin, demethoxycurcumin, and bisdemethoxycurcumin in the extracts were in the range of 12.57–18.41, 6.29–9.99, and 9.55–15.68% (w/w), respectively when determined by TLC-densitometry. By HPLC, the contents of these compounds were 8.55–15.88, 1.50–4.16, and 5.54–9.33% (w/w), respectively. Free radical scavenging activity of the ethanolic extracts of C. longa was evaluated using DPPH scavenging method. EC₅₀ values of all extracts ranged from 18.24–26.36µg/ml. The content of these bioactive compounds and the free radical scavenging activity of the extracts will be useful as a guidance for further standardization of turmeric extracts used in pharmaceutical and cosmetic products.

Acknowledgements: This study was supported by research grants from Drug program of National Research Council of Thailand (NRCT), Mahidol University, Bangkok, Thailand and ASEA UNINET.

References: [1] Apisariyakul A, Vanittanakorn N, et al. (1995) J Ethnopharmocol 49: 163–69. [2] Masuda T, Jitoe A, et al. (1993) Phytochemistry 32(6): 1557–60.