Impact of extraction processes on the 6-shogaol content in Zingiber officinale (Halia Penang) and its antiproliferative activities on human colorectal cancer cell lines (HT-29)

Ginger has been reported to possess potential antiproliferative activities and it is mainly attributed to the presence of gingerols and shogaols. Recent studies show that 6-shogaol is most potent when compared to 6-gingerol [1]. It was also reported that 6-gingerol is converted to 6-shogaol during drying or long-term storage of ginger [2]. However, there are no reports on the impact of different extraction processes on the 6-shogaol content in ginger and its antiproliferative activities. In this study, the impact of extraction processes on the 6-shogaol content in Zingiber officinale (Halia Penang) and its antiproliferative activities on HT-29 cell lines was determined. Ginger rhizomes were collected from local market of Penang and dried at room temperature, in hot air oven (60°C and 80°C) and in microwave (110W, 550W and 1100W). Dried gingers were extracted with methanol and dichloromethane (DCM) in sonicator and concentrated in rotary evaporator. The 6-shogaol concentrations in extracts were determined using HPLC. Percent cell inhibitions (%) on HT-29 cells were determined using MTT assay. Among the 3 drying methods, the microwave drying offered the highest 6-shogaol content. Among the extraction solvents, methanol was found to be better solvent than DCM in extracting 6-shogaol. However, DCM extracts showed higher percent cell inhibition than that of methanol extracts. It was also found that there was no correlation between antiproliferative activities of ginger extracts and the corresponding 6-shogaol contents. Hence, the antiproliferative activities of ginger are not only due to 6-shogaol, but also due to other secondary metabolites.

References: [1] Sang S, Hong J, et al. (2009)J Agric Food Chem, 57 (22): 10645–50. [2] Zhang X, Iwaoka WT, et al. (1994)J Food Sci, 59(6): 1338–1340.