Purification Methods of Patchouli Alcohol
The quality of patchouli oil is determined by the content of patchouli alcohol, which is influenced by many factors, as discussed in previous articles. To produce the patchouli oil with a certain grade of patchouli alcohol, the patchouli alcohol must be purified. Experimental results on the practical purification of patchouli alcohol using various methods have been reported by researchers, as described below.
1. Membrane filtration
The membrane allows larger molecules to retain through and passes the smaller molecules depending on the pore size of the membranes. Membrane filtration technology, namely microfiltration, ultrafiltration, nanofiltration, and reverse osmosis, has been applied frequently to recover, purify, and concentrate the phenolic compounds from plant material extracts (Cassano et al., 2018). Donelian et al. (2016) tried to use the membrane filtration technique using reverse osmosis and nanofiltration membranes to increase the content of patchouli alcohol in the oil. Unfortunately, this technique was not able to elevate the quality of patchouli oil.
2. High-performance centrifugal partition chromatography (HPCPC)
HPCPC is a chromatography technique based on the general principles of liquid-liquid partitioning. This purification method uses two immiscible liquid as the mobile and stationary phases. Dang et al. (2010) isolated six volatile compounds, curdione (2.7% yield, w/w), curcumol (1.3%), germacrone (3.3%), curzerene (6.0%), and 1,8-cineole (3.0%), by CPC from the essential oil of Curcuma wenyujin using a nonaqueous two-phase solvent system. A preparative purification of patchouli alcohol using HPCPC method showed a rapid and effective method for one-step separation using a solvent mixture of petroleum ether and acetonitrile (Li et al., 2011). The purity of patchouli alcohol can reached up to 98% with the yield of ~16%. However, this method is required the use of organic solvents and has a low yield of the patchouli alcohol.
3. Molecular distillation
Molecular distillation separates the molecules by distillation under vacuum at a temperature far below its boiling point (Zhang et al., 2018). This purification method has been applied for obtaining the thermally sensitive molecules, such as essential oil, vitamins, free fatty acids, and others, as well as for maintaining natural properties of the targeted compound. The molecules are in contact with heat for a short time under high vacuum due to the small distance between evaporation and condensation surfaces (Ketenoglu and Tekin, 2015). Chen et al. (2009) reported that the purification of patchouli alcohol from patchouli oil by molecular distillation using the evaporation temperature at 65°C could produce the patchouli alcohol with the purity up to 40.71%. Dantas et al. (2020) did the optimization process of molecular distillation from patchouli oil to obtain patchouli alcohol rich fraction. They were able to obtain 62.3% of patchouli alcohol in the residue with 74.2% recovery percentage.
At PT Mitra Ayu, we utilizes the Molecular distillation technology to process our Patchouli oil iron free, Patchouli oil MD and Patchouli alcohol 65%.
4. Fractional distillation combined with crystallization
These methods are successfully applied to purify of patchouli alcohol from patchouli oil in solvent-free condition (Su et al., 2014). The purity of patchouli alcohol using the fractional distillation was 86.4%. Its purity increased to 99.0% in the crystal form and the total yield reached 52.9% resulted by the combination of these methods.
5. Host-guest inclusion crystalline method
Principle of this method is based on the molecular recognition and interaction between the host and guest molecules to achieve the separation of a single effective component from the crude extracts. This method showed a simple, rapid, and effective separation of patchouli alcohol from the patchouli oil with 100% purity. Unfortunately, there was no information for the yield of this purification (Tong et al., 2013).
6. Column chromatography
Column chromatography, a type of adsorption chromatography, is applied to the separation of natural products, especially in the initial separation stage, due to its simplicity, high capacity, and low cost of adsorbents such as silica gel. Zhang et al. (2018) revealed that around 90% of phytochemical separation in preparative scale was based on silica gel. A flash chromatography on silica gel using a mixture of n-hexane and ethyl acetate as eluent was used to purify the patchouli alcohol from a chemical synthesis solution with the yield of 38% (Xu et al., 2017). Kang et al. (1998) developed the isolation method of patchouli alcohol from patchouli oil by column chromatography using a normal phase elution system of n-hexane and ether mixture on silica gel.
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References
Cassano, A., Conidi, C., Ruby-Figueroa, R., and Castro-Munoz, R. (2018). Nanofiltration and tight ultrafiltration membranes for the recovery of polyphenols from agro-food by-products. International Journal of Molecular Sciences, 19: 351.
Chen, H., Zhang, J., Zhu, H., and Song, Z. (2009). Purification of patchouli alcohol in volatile oil of Pogostemon cablin by molecular distillation. Chinese Traditional and Herbal Drugs, 40: 60–63.
Dang, Y.Y., Li, X.C., Zhang, Q.W., Li, S.P., and Wang, Y.T. (2010). Preparative isolation and purification of six volatile compounds from essential oil of Curcuma wenyujin using high-performance centrifugal partition chromatography. Journal of Separation Science, 33: 1658–1664.
Dantas, T.N.C., Cabral, T.J.O., Neto, A.A.D., and Moura, M.C.P.A. (2020). Enrichmnent of patchoulol extracted from patchouli (Pogostemon cablin) oil by molecular distillation using response surface and artificial neural network models. Journal of Industrial and Engineering Chemistry, 81: 219–227.
Donelian, A., de Oliveira, P.F., Rodrigues, A.E., Mata, V.G., and Machado, A.F. (2016). Performance of reverse osmosis and nanofiltration membranes in the fractionation and retention of patchouli essential oil. The Journal of Supercritical Fluids, 107: 639–648.
Kang, S.S., Kim, J.S., Chi, H.J., and Won, D. (1998). Isolation and quantitative determination of patchouli alcohol from Pogostemon cablin Benth. Korean Journal of Pharmacognosy, 29: 18-21.
Ketenoglu, O., and Tekin, A. (2015). Applications of molecular distillation technique in food products. Italian Journal of Food Science, 27: 277–281.
Li, X.-C., Zhang, Q.-W., Yin, Z.-Q., Zhang, X.-Q., and Ye, W.-C. (2011). Preparative separation of patchouli alcohol from patchouli oil using high performance centrifugal partition chromatography. Journal of Essential Oil Research, 23: 19–24.
Su, Z.Q., Wu, X.L., Bao, M.J., Li, C.W., Kong, S.Z., Su, Z.R., Lai, X.P., Li, Y.C., and Chen, J.N. (2014). Isolation of patchouli alcohol from patchouli oil by fractional distillation and crystallization. Tropical Journal of Pharmaceutical Research, 13: 359–363.
Tong, J., Yuan, L., Guo, F., Wang, Z.-H., Jin, L., and Guo, W.-S. (2013). Selective separation of patchouli alcohol from the essential oil of Cablin potchouli by inclusion crystalline method. Natural Product Research (Formerly Natural Product Letters), 27: 32–36.
Xu, G.-Q., Lin, G.-Q., and Sun, B.-F. (2017). Concise asymmetric total synthesis of (–)-patchouli alcohol. Organic Chemistry Frontiers, 4: 2031–3033.
Zhang, Q.-W., Lin, L.-G., and Ye, W.-C. (2018). Techniques for extraction and isolation of natural products: a comprehensive review. Chinese Medicine, 13: 20.
