Oxidation during Fresh Plant Processing: A Race against Time

Abstract

Oxidation is a major concern in the food and cosmetics industry; however, little information is available in the literature about its effect during the production of herbal medicines. The impact of oxidation on herbal mother tincture (MT) manufacturing was investigated by performing an oxidative stress test, in which cryogenically ground fresh plants (Echinacea purpurea, Mentha piperita, Ginkgo biloba, and Hypericum perforatum) were exposed to air in a time-controlled manner before extraction. The effect of oxidation on the resulting extracts was evaluated using UV–Vis spectroscopy and potassium permanganate antioxidant assay. Furthermore, a tyrosinase enzymatic assay was performed on MTs to evaluate the behavior of the absorbance spectra of phenolic compounds during oxidation. Additionally, several commercially available herbal mother tinctures were examined for oxidative changes. The exposure of the fresh plant material to air for 30 min decreased the antioxidant activity in all four tested plants by 10% to 44%. This decrease occurred along with an intensity diminution and flattening of the typical UV–Vis absorption spectra of the MTs. The results have shown that the impact of oxidation during MT manufacturing is a serious issue and could be monitored by means of simple UV–Vis spectra recording.