β-Sitosterol: supercritical carbon dioxide extraction from sea buckthorn (Hippophae rhamnoides L.) seeds

Abstract

Supercritical fluid extraction represents an efficient and environmentally friendly technique for isolation of phytosterols from different plant sources. Sea buckthorn (Hippophae rhamnoides L.) seeds were extracted with supercritical carbon dioxide at pressures ranging from 15-60 MPa and temperatures of 40-80 degrees C. Oil and β-sitosterol yields were measured in the extraction course and compared with Soxhlet extraction with hexane. The average yield of β-sitosterol was 0.31 mg/g of seeds. The maximum concentration of β-sitosterol in the extract, 0.5% w/w, was achieved at 15 MPa, 40 degrees C, and a carbon dioxide consumption of 50 g/g of seeds. The extraction rate was maximal at 60 MPa and 40 degrees C. Both β-sitosterol yield and its concentration in the extract obtained with hexane were lower than with carbon dioxide.

Keywords: Hippophae rhamnoides L.; fractionation in time; sea buckthorn seed; supercritical carbon dioxide; β-sitosterol.

Figure 1.

Extraction curves for the sea buckthorn seed oil. See Table 1 for the extraction conditions of experimental runs 1–5 (curve 1 to 5).

Figure 2.

Extraction curves for β-sitosterol. For the extraction conditions of run 1–5 (curve 1 to 5) refer to Table 1.

Figure 3.

Relationship between β-sitosterol yield and total extract yields. For the extraction conditions of run 1–5 (curve 1 to 5) refer to Table 1.

Figure 4.

A scheme of the experimental device: 1-high pressure pump, 2-controlling unit, 3-input valve for carbon dioxide, 4-air-conditioned box, 5-extraction column, 6-expansion valve, 7-vial containing the extract, 8-flow meter.