Optimization of microwave-assisted extraction of zerumbone from Zingiber zerumbet L. rhizome and evaluation of antiproliferative activity of optimized extracts

BACKGROUND The extraction of bioactive compounds from herbal materials requires optimization in order to recover the highest active dose. Response surface methodology was used to optimize variables affecting the microwave extraction of zerumbone from Zingiber zerumbet using the Box-Behnken design. The influence of variables, such as ethanol concentration (X1), microwave power (X2), irradiation time (X3), and liquid-to-solid ratio (X4), on the extraction of zerumbone was modeled using a second-order regression equation. The antiproliferative activity of optimized and non-optimized extracts was evaluated against the HeLa cancer cell line using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. RESULTS Two linear parameters, X1 and X4, and their quadratic parameters were highly significant at the P < 0.01 level. Two interaction parameters, X1X4 and X2X3 were significant, whereas interactions of X1X2, X1X3, X2X4 and X3X4 were insignificant (P > 0.05). The optimum microwave extraction conditions were as follows: ethanol concentration, 44%; microwave power, 518 W; irradiation time, 38.5 s; and liquid-to-solid ratio, 38 mL/g. Under these conditions, the maximum zerumbone yield was 5.88 mg/g DM, which was similar to the predicted value (5.946 mg/g DM). Optimized and non-optimized Z. zerumbet rhizome extracts exhibited significant antiproliferative activity against HeLa cancer cells, with half-maximal inhibitory concentration (IC50) values of 4.3 and 7.8 μg/mL, respectively, compared with 1.68 μg/mL for the anticancer drug cisplatin. When the extract concentration increased from 4.3 to 16.0 μg/mL, the inhibition of cancer cell growth increased from 50.0 to 79.5%. CONCLUSIONS In this study, the optimized microwave protocol developed for extracting zerumbone from Z. zerumbet was faster and consumed less solvent than previous methods, while improving and enhancing the antiproliferative activity.