Mid-Term Exam Answers Chemistry of Natural Products

1. Extraction with supercritical fluid

fig. 1 supercritical fluid

To improve the productivity and increase the quality of the extraction of the active compounds of natural ingredients is the diversification of the isolation of natural products. During this period, the local industry is still based on conventional separation technologies such as steam distillation or extraction with organic solvents. If we start with separation using supercritical fluid technology. Besides staying as digadang separation technology greener, supercritical fluid also offers a performance that is often superior to conventional technologies. In fact, this technology has been used for the removal of caffeine in coffee.

fig. 2 Fluid phase diagrams and territories supercritis

In a nutshell the fluid is a supercritical fluid in a state above the critical temperature and pressure so as not to show any phase separation. Supercritical fluid can diffuse in a solid-like behavior of gases or other substances may dissolve as liquid behavior. So far that is commonly used in the extraction is a mixture of natural material supercritical fluid CO2 (carbon dioxide). Moreover, CO2 methanol, or a combination dimetilether with additive methanol, dimetilether, or the water can also be applied to the separation of the active compound.

use of supercritical CO2 is more advantageous in the extraction process especially to reach the supercritical state has enough pressure 73.9 bar and temperature of 31.1 ° C, which is said relatively soft (compared to methanol which require conditions of 239.5 ° C and 81 bar). CO2 in supercritical conditions, a variety of target compounds will be no change or chemical damage. The course of the process can be fairly simple and can be applied directly on the solid material, such as shredded leaves. After solubilization and extraction process repeatedly, fluid mixture and the active ingredient may be separated with a lower pressure. CO2 supercritical fluid has properties of non-polar and easier to melt the fat while the most active compounds that have economic value is polar. The problem is easily solved in the process of extraction liquid with a little 'longer as a regulator of polarity, such as water or methanol. Many studies have shown that the extraction with supercritical fluid selectivity is higher using conventional means. It is mainly influenced by the physico-chemical properties of the fluid and mass transfer occurring. Meanwhile, if the separation were performed using solvents water, as the system of steam distillation, almost all of the polar active compounds will be transported.

2. Natural ingredient compounds can be synthesized in the laboratory by:

• Cold extraction

          a. Maceration method The maceration is a penyarian easily done by immersing the powder in the  liquid botanical penyari for a few days at room temperature and protected from light. Maceration method used to sum up bulbs that contains chemical Komonen penyari soluble liquid, containing benzoin, tiraks and candles.

The advantage of this method is simple equipment. Moderate losses include the time required to extract the sample long enough, penyari fluids are being used more, can not be used for materials that have a hard texture as benzoin, tiraks and candles.

Maceration method can be modified as follows:

 Change maceration circular

 Change digestion maceration

 Change Maceration circular Multi

 Change remaserasi

 Changes stirrer machine

 Soxhletasi Methods

          b. Soxhletasi is penyarian vegetable sustainable, heated so as to evaporate the liquid penyari, penyari liquid molecules of condensed vapor in the water for cooling back and summarize raw klongsong and then again in round-bottomed flask after passing through the siphon tube. 

The advantage of this method is:

- Can be used to sample the texture is soft and not resistant to direct heating.

- Used or less solvent

- or heating can be arranged

The disadvantage of this method:

- Since the solvent is recycled, extract collected in a container near the heated continually so as to cause a decomposition reaction by heat.

The total number of compounds or extracts will exceed their solubility in specific solvents that can solve in the container and need more volume of solvent to dissolve it.

- When done on a large scale, may not be suitable for use with solvent boiling point is too high, such as methanol or water, since all the tools are under komdensor must be at this temperature for the effective movement of solvent vapors .

This method is limited to the extraction of the pure solvent or mixture of azeotropic and can not be used for the extraction with a mixture of solvents, such as hexane: diklormetan = 1: 1, acidified or basified solvent, since the steam will have a different composition in the liquid solvent into the container.

            c. Percolation Method : Percolation is a way to transmit penyarian penyari through raw powder that has dibasahi.Keuntungan this method does not require the additional step of solid samples (marc) was separated from the extract. The disadvantage is that the contact between the solid sample is irregular or limited with respect to the reflux, and the solvent to cool during the process so that it does not dissolve the components percolation efficient.

• Heat extraction

           a. Method of reflux

The advantage of this method is used to extract samples that have a rough texture and keep the direct heating 

The disadvantage is the need of the total volume of the solvent and a manipulation of the operator.

           b. Method of steam distillation

Steam distillation is a popular method for the extraction of oils evaporate (essential) from plant samples

A method of steam distillation is intended to summarize containing crude oil evaporates or contain chemical components that have a high boiling point at normal atmospheric pressure.

3. Selection of Proper Solvent

The choice of solvent is perhaps the most critical step in the process of recrystallization since the correct solvent must be selected to form a product of high purity and in good recovery or yield. Consequently a solvent should satisfy certain criteria for use in recrystallization. The desired compound should be reasonably soluble in the hot solvent, about 5 g/100 mL (5 mg/100 μL)

being satisfactory and insoluble or nearly insoluble in the cold solvent. Note that the reference temperature for determination of the solubility in "cold" solvent is often taken to be room temperature. This combination of solute and solvent will allow dissolution to occur in an amount of solvent that is

not unduly large and will also permit recovery of the purified product in high yield. A solvent having thistype of solubility properties as a function of

temperature would be said to have a favorable temperature coefficient for the desired solute.

Conversely, the impurities should either be insoluble in the solvent at all temperatures or must remain at least moderately soluble in the cold solvent. In other words, if the impurities are soluble, the temperature coefficient for them must be unfavorable; otherwise the desired product and the impurities would both crystallize simultaneously from solution. The boiling point of the solvent should be low enough so that it can readily be removed from the crystals. The boiling point of the solvent should generally be lower than the melting point of the solid is being purified. The solvent should not react chemically with the substance being purified. The chemical literature is a valuable source of information about solvents suitable for recrystallizing known compounds. If the compound has not been prepared before, it is necessary to resort to trial-and-error techniques to find an appropriate solvent for recrystallization. The process of selection can be aided by consideration of some generalizations about solubility characteristics for classes of solutes. Polar compounds are normally soluble in polar solvents and insoluble in non-polar solvents, for example, whereas non-polar compounds are more soluble in non-polar solvents. Such characteristics are summarized by the adage, "like dissolves like." Of course, although a highly polar compound is unlikely to be soluble in a hot, non-polar solvent, it may be very soluble in a cold, very polar solvent. In this case, a solvent of intermediate polarity may be the choice for a satisfactory recrystallization. Occasionally a mixture of solvents is required for satisfactory recrystallization of a solute. The mixture is usually comprised of only two solvents; one of these dissolves the solute even when cold and the other one does not.

4. To determine the structure of a compound of natural ingredients can be determined :

• Liquid chromatography coupled to UV-detection (LC–UV)
• Liquid chromatography coupled to electrospray ionisation quadrupole ion trap mass spectrometry (LC–ESI–MS/MS)
• Near infrared reflectance spectroscopy (NIRS)

Analysis of HNMR of Caffeine

 H’NMR Spectrum for Caffeine

Empirical Formula: C8H10N4O2
Molecular Weight: 194.1906
Nominal Mass: 194 Da
Average Mass: 194.1906 Da
Monoisotopic Mass: 194.080376 Da

The HNMR spectrum for caffeine is clearly in D2O. There is a strong singlet at 4.8. Therefore, no protons on hydroxyl or carboxyl groups will be visible in the HNMNR spectrum.

The single hydrogen on the cyclopentene structure will be a singlet at approximately 7.9ppm. The proton is bound to a carbon that is double bound to nitrogen. Normally, vinyl protons fall in the 5-6 range. However, since the carbon is double bound to nitrogen, it may account for the higher ppm in this particular peak. There is no proton that this specific hydrogen can couple with. After counting two to three bond lengths away, there is no other proton. Using the N+1 rule, this would be a singlet. This specific hydrogen will show a singlet at 7.9ppm.

The methyl group that is bound to the nitrogen in the cyclopentene structure will show a singlet at approximately 3.9ppm. The range for a proton bound to a carbon that is bound to a halogen or oxygen is 3-4. However, this particular methyl group is bound to nitrogen that is adjacent to a vinyl group on each side. This particular methyl group has a higher ppm number than the two other methyl groups. Vinyl groups fall in the 5-6 range and this would raise the ppm number of this particular methyl group. Again, counting two to three bond lengths away, there is no proton to couple with. Using the N+1 rule, this would be a singlet. Therefore, this would be a singlet at 3.9ppm.

The final methyl group bound to the nitrogen is adjacent one carbonyl group and one vinyl group. This peak is a singlet at 3.4ppm. The range for a proton bound to a carbon that is bound to a halogen or oxygen is 3-4. The range for a vinyl group is 5-6. This peak is slightly higher than the methyl that is adjacent to two carbonyl groups because this specific methyl group is adjacent to one vinyl group. Counting two to three bond lengths away, there is no other proton for coupling. Therefore, using the N+1 rule, this would be a singlet.