Subcritical Water Extraction of Antioxidant Compounds from Rosemary Plants

TLDR

Subcritical water extraction at 25–200 °C selectively isolates rosemary antioxidants, with fractions characterized by LC‑MS and DPPH assays to assess temperature‑dependent efficiency. The extracts showed high selectivity for active rosemary compounds such as carnosol, rosmanol, carnosic acid, methyl carnosate, cirsimaritin, and genkwanin, and exhibited strong antioxidant activity (~11.3 µg/mL), comparable to supercritical fluid extraction.

Abstract

Subcritical water extraction at several temperatures ranging from 25 to 200 degrees C has been studied to selectively extract antioxidant compounds from rosemary leaves. An exhaustive characterization of the fractions obtained using subcritical water at different temperatures has been carried out by LC-MS, and the antioxidant activities of the extracts have been measured by a free radical method (DPPH). Results indicate high selectivity of the subcritical water toward the most active compounds of rosemary such as carnosol, rosmanol, carnosic acid, methyl carnosate, and some flavonoids such as cirsimaritin and genkwanin. The antioxidant activity of the fractions obtained by extraction at different water temperatures was very high, with values around 11.3 microg/mL, comparable to those achieved by SFE of rosemary leaves. A study of the effect of the temperature on the extraction efficiency of the most typical rosemary antioxidant compounds has been performed.