Phytochemicals, antioxidants and anti-tyrosinase analyses of selected ginger plants

Abstract

Background: Some of Zingeberaceae are not widely used for medicine of food, although in Thailand have been used them for many reasons about health or the diet. This study evalued the phytochemicals and anti-tyrosinase activities of 16 plant species of Alpinia, Amomum, Curcuma, Etlingera and Kaemferia (Zingiberaceae). Methods: The extractions of dried powdered rhizomes were performed using n-hexane, ethylacetate and ethanol. Percentage extract yield of the samples varied among species and solvent extracts. Chemical groups (alkaloids, flavonoids, tannins, polyphenols, steroids and terpenoids) were identified using phytochemical screening. The total phenolic contents (TPC) were analyzed using the Folin-Ciocalteu's reagent, while antioxidant activities were detected using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the 2,2'-azino-bis (3-ethylbenzothizoline-6-sulphonic acid) (ABTS.+). The anti-tyrosinase was expressed to the half maximal inhibitory concentration (IC50) value (mg/mL). Results: The ethyl acetate extract of Amomum showed the highest value of TPC. The strongest antioxidant activity were found in Amomum and Kaemferia extracts, while ethyl acetate and ethanol extracts of all samples have a better antioxidant properties than the n-hexane extracts. On the other hand, the n-hexane extracts have the highest anti-tyrosinase potential in all samples and of these, Curcuma extracts were the best group. Conclusion: Our research indicated that plants of the Zingiberaceae would be new sources of antioxidants and anti-tyrosinase for further natural product developments in cosmetics, food or nutraceuticals.