Physico-Chemical Characteristics and Stability of Essential Oil from Dried Leaves of Pogostemon heyneanus Benth.

Abstract

Essential oils were extracted from air-dried leaves of Pogostemon heyneanus Benth. (Indian patchouli) by steam distillation using a Clavenger tube. Physico-chemical properties of the oil like acid value, ester value, optical rotation, refractive index, saponification value, solubility in 90% ethanol, specific gravity, % alcohol, and % aldehyde was deter-mined. Stability studies of the essential oil included the determination of the effect of light, length of storage and temperature. Based on the set standards, the physico-chemical properties of Pogostemon heyneanus Benth. oil do not fall within the specifications for the oils of patchouli. However, these properties may improve later because the quality of the oil could improve through time. Percent alcohol of the oil samples exposed to both light and dark conditions decreased while their percent aldehyde increased. Thin-layer chromatograms showed that middle spots of   polar components were not detected under low temperature after 2 hours and more of exposure. At room temperature, at 800C, 1 IOOC, and 1400C, the same number of spots were observed after 2 hours and beyond but at 1700C and boiling point temperatures, an increased number of spots was observed. TLC results of samples exposed to light and dark conditions, respectively, showed an increased number of spots on the fifth month of storage while the samples became more viscous and their color changed from light yellow to yellow-orange.