Terpene degradation and extraction from basil and oregano leaves using subcritical water

In the first part of this study, the stability of five terpenes (α-pinene, limonene, camphor, citronellol, and carvacrol) under subcritical water conditions was investigated. The stability studies were carried out at four different temperatures (100, 150, 200, and 250 °C) with two different heating times (30 and 300 min). When water temperature was increased, the degradation of terpenes became more serious. Prolonged exposure time to each heating temperature also caused decreased terpene stability. The terpene recoveries were determined by conducting subcritical water extraction of sand spiked with terpenes. The recoveries are typically around 70 to 80% for extractions at 100 °C. Terpene recoveries were decreased with increasing water temperature due to poorer stability of terpenes. After the degradation and recovery studies, basil and oregano leaves were extracted using water at both 100 and 150 °C. The concentrations of each individual terpene in the water extract generally ranged from trace quantity to 65 μg terpene/g herb. However, the concentration of carvacrol in the oregano-water extract at 150 °C was found to be as high as 4270 μg carvacrol/g oregano.