Antioxidant activity and phenolic compounds of ginger (Zingiber officinale Rosc.) determined by HPLC-MS/MS

Eugenol (4-allyl-2-methoxyphenol), a major phenolic component from clove oil (Eugenia caryophyllata), has several biological activities. To estimate the capacity of eugenol to act as an antioxidant, the following were studied: 1,1-diphenyl-2-picryl-hydrazyl-, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)-, and N,N-dimethyl-p-phenylenediamine-scavenging activity; total antioxidant activity; and ability to reduce ferric ions and cupric ions. Eugenol inhibited 96.7% (r(2)=0.9319) lipid peroxidation of a linoleic acid emulsion at a 15-μg/mL concentration. Butylated hydroxyanisole, butylated hydroxytoluene, α-tocopherol, and Trolox(®) displayed 95.4% (r(2)=0.8482), 99.7% (r(2)=0.7798), 84.6% (r(2)=0.9272), and 95.6% (r(2)=0.8511) inhibition of peroxidation, respectively, at the 15-μg/mL concentration. According to the results of this study, eugenol had the most powerful antioxidant activity and radical-scavenging activity. This study should prompt further studies of the antioxidant properties of eugenol.

Propolis, an extremely complex resinous material, exhibits valuable pharmacological and biological properties attributed to the presence of polyphenols. In this study, we determined the antioxidant properties of lyophilized aqueous extract of propolis (LAEP) from Erzurum province of Turkey and correlated the values with total levels of polyphenolic compounds. In order to estimate the capacity of LAEP to act as antioxidants, we studied its 1,1-diphenyl-2-picryl-hydrazyl radicals (DPPH()), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS()(+)), N,N-dimethyl-p-phenylenediamine radicals (DMPD()(+)), superoxide anion radicals (O(2)(-)) and hydrogen peroxide (H(2)O(2)) scavenging activity, total antioxidant activity, ferric ions (Fe(3+)) and cupric ions (Cu(2+)) reducing ability, ferrous ions (Fe(2+)) chelating activity. LAEP inhibited 93.2% lipid peroxidation of a linoleic acid emulsion at 30 microg/mL concentration. On the other hand, BHA, BHT, alpha-tocopherol and trolox displayed 83.3%, 82.1%, 68.1% and 81.3% inhibition of peroxidation at the same concentration, respectively. Quantitative amounts of caffeic acid, ferulic acid, syringic acid, ellagic acid, quercetin, alpha-tocopherol, pyrogallol, p-hydroxybenzoic acid, vanillin, p-coumaric acid, gallic acid and ascorbic acid were detected by high performance liquid chromatography and tandem mass spectrometry (LC-MS/MS). This study will bring an innovation for further studies with regard to the antioxidant properties of LAEP.