Physico-Chemical Properties and Thermal Analysis of Silybum Marianum of Dera Ismail Khan and Kohat Regions

Abstract

Silybum Marianum and Sunflower seeds were collected from Dera Ismail khan (31º49′N 70º55′E) and Kohat (33º35′N 71º26′E) regions. The oils were soxhlet extracted using n-hexane (40-60 °C). The oils samples were placed at ambient temperature (25-30 °C). Fatty acid composition of oils was determined by Gas Chromatography, Fourier Transform Infrared and thermal stability were investigated by Thermogravimetric Analysis. Gas Chromatographic analysis showed that fatty acid composition of Silybum Marianum oil of the two regions differs in their unsaturated fatty acids like oleic acid (20.13, 12.34 %), linoleic acid (59.85, 65.24 %). Similarly, saturated fatty acids such as palmitic acid (2.14, 4.25 %), stearic acid (20.17, 3.76 %) also differed significantly.  FT-IR analysis sowed about the same components in both SMO and SFO. The presence of C-H stretching of alkyl group at 2921, 2852 cm^-1 with 80 % absorbance and at 1743 cm^-1 the presence of carbonyl group was confirmed with 85 % absorbance in both the oils. TG analysis showed that SMO of D.I. Khan region were thermally less stable and showed 15-18 % ± 1.3SD degradation and Kohat region showed 0 % degradation in 1st phase at 250 °C.  These changes in composition of fatty acids were attributed to climatic difference of D.I. Khan and Kohat regions.  

      Keywords: Silybum Marianum, thermogravimetric analysis, infrared spectroscopy,