Microwave assisted extraction for determination of curcuminoid content in Curcuma longa rhizome

Curcuma longa rhizome is a well-known herb that has been traditionally used in many countries. In Thailand C. longa have been added into the national drug list and widely used for treatment of dyspepsia instead of simethicone. Curcuminoid content in C. longa rhizome was used for control the quality of the raw material as described in Thai Herbal Pharmacopoeia (THP) [1]. The extraction method mentioned in THP was time consuming, it was performed by macerated C. longa powder in tetrahydrofuran for 24 hr before analyzed with UV spectrophotometer. This study aimed to investigated the novel extraction method which are faster but still precise and accurate as well as the conventional method. Three different extraction methods including reflux extraction (RE), microwave assisted extraction (MAE) and ultrasonic assisted extraction (UAE), have been investigated and compared with the conventional method. It was found that MAE (900W, 30 s on/30 s off for 3 cycle) and UAE (90W, 37 kHz for 30 min) were able to extract curcuminoids as well as maceration for 24 hr, while RE for 30 min gave lower amount of curcuminoid content. Some parameters of MAE were optimized including power, cycle and extraction time. The optimized conditions were then evaluated on their intraday and interday precision in 40 samples both raw materials and commercial products. The result showed that the most appropriate conditions of MAE for extraction of curcumionoids were 900W, 25 s on/30 s off for 4 cycle which showed %RSD at 0.55% and 1.23% for intraday and interday precision, respectively. MAE was able to use as an alternative extraction method to the conventional one. The method is faster easier and more suitable for the routine analysis of curcuminoid content than the conventional method.

Fig. 1: curcuminoid content (%)

[1] Department of Medical Sciences. Thai Herbal Pharmacopoeia, 1. Bangkok: Prachachon Co; 1995