Introduction
Natural products are defined as small molecules found in bacteria, plants, and other living Organisms. These products are used in a variety of industries, including medicines, foods, perfumes, dyes, and pesticides. However, their main purpose is to serve as a template for the synthetic production of the product, or to provide an intermediate in the production of semi synthetic drugs. According to the U.S. National Cancer Institute, only 33% of new drugs are entirely synthetic, meaning two thirds of all new drugs are derived from natural products. One of the largest obstacles in the field of natural products is the technologies needed to isolate and purify the products from their natural habitat. Many techniques exist in order to overcome this obstacle, including extraction, chromatography, and distillation.
Extraction is the process of pulling something out of its natural environment. One of the most well-know examples is the process of brewing tea or coffee. Hot water is used to extract smaller, more polar molecules from the solid (such as caffeine), leaving behind larger, less soluble compounds. Although many different types of extraction exist, this process is called solid-liquid extraction, as liquid is used to extract components from a solid. Solid-liquid extraction can also used in the process of obtaining piperine, which composes 5-9% of black pepper. In this case, hot dichloromethane is used to extract piperine from ground black pepper. Similar to brewing a cup of tea, the remaining pepper grounds can then be filtered from the solution, resulting in a dichloromethane solution that contains, among other components, piperine.
Although piperine has been used in forms of medicine and as an insecticide for years, recent discoveries have made its isolation and purification even more important. For instance, studies show that piperine, an antioxidant, is able to offer protection to DNA against γ-radiation. Not only could this provide protection to radiation exposure, but also to normal tissues during radiotherapy. Piperine has also been shown to exhibit a chemopreventive effect against procarcinogens. Studies have shown that piperine decreases the effects of aflatoxin, a cancer causing substance, as well as reduce the risk of liver disease. Clearly, recent discoveries have greatly increased the importance of isolation and purification of piperine.
In this experiment, piperine was extracted from ground black pepper by solid-liquid extraction, using dichloromethane as the liquid extractant. The product was isolated by crystallization, and characterized by melting point, TLC, IR, H NMR, and MS.
Experimental
10.0 g of pure ground pepper were added to 20 mL of dichloromethane. The solution was heated and allowed to reflux for 20 minutes, while stirring. The solution was then vacuum filtrated, and the pepper grounds washed with dichloromethane (1x10mL). The dichloromethane
was evaporated from the liquid filtrate, resulting in dark brown oil. 6 mL of ether was added to the oil, which was then cooled in an ice bath with stirring for 5 minutes. The solvent was evaporated, and 6 mL of ether was added once again, while cooling in an ice bath for 15 minutes. Small, yellow crystals began to precipitate out. The solution was vacuum filtrated, and the yellow crystals (2.63 g, 2.63% recovery, 37.5% yield) were washed with cold ether (2x4 mL). TLC analysis was conducted on the initial liquid filtrate and the product using 60% acetone in hexanes. The melting point of the product was 132-134 oC, and IR, H NMR, and MS spectra were obtained.
Results, Discussion, and Conclusion
In this experiment, piperine was extracted from ground black pepper using dichloromethane. The product was characterized by melting point, TLC, IR, H NMR, and MS. Isolation of natural products is an important aspect of organic chemistry, as many new drugs derive from them. For instance, piperine has recently been found to aid in protecting from radiation, as well as act as a combatant to procarcinogens. Thus, it is more important than ever to be able to isolate piperine from its natural habitat, black pepper.
Piperine was successfully isolated from black pepper with a percent recovery of 2.63% and percent yield of 37.5%, which is relatively high. The product was small yellow crystals with a melting point of 132-134oC, which is in the theoretical range of 131-135 o C reported in the literature, indicating high purity. TLC analysis also indicates high purity, as the initial liquid filtrate contained two dots (Rf = .804, .518), and the product lane contained use one dot (Rf=.518), which can be presumed to be piperine. Mass spec revealed a molecular weight of 285, which matches the molecular weight of piperine. Also, fragmentation patterns indicate the presence of a piperidine fragment, which matches with the structure of piperine. H NMR data was obtained and confirms the identity of the product, as indicated by the 7 hydrogens in the aromatic/conjugated alkene range (6.301-7.259 ppm). Additionally, the peak at 5.974 ppm is a singlet, which corresponds to the hydrogens bonded to the carbon between two oxygens on piperidine. Finally, IR data indicates the presence of an amide (1630.6 cm-1), as well as aromatic and aliphatic C-H bonds, (2937.3 cm-1, 2854.0 cm-1). All signals were annotated accordingly, and matched the predicted spectra for piperine, indicating that the desired product has been isolated.
In conclusion, piperine was successfully isolated with high purity. Possible improvements could be made to the experiment to improve the % recovery of the piperine, such as increasing the time the black pepper is refluxed.