Semester Exam Chemistry of Natural Products

Name  : Yulia

Nim     : RSA1C110015

  

1.1.   Explain the triterpenoid biosynthetic pathway, identify important factors that determine the quantities produced many triterpenoids.

Answer :

Triterpenoid carbon skeleton is a compound derived from six isoprene units and the biosynthesis derived from C30 acyclic hydrocarbons, ie skualena.

Biosynthesis of triterpenoid :

Biosynthesis tritepenoid starting from compound squalene derived from mevalonic biosynthetic pathways whereby acetic acid is activated by coenzyme A that will menghasilkkan IPP and IPP is synthesized to form squalene, and squalene with the assistance of the NADH + H + and NADH + + H2O will produce compound 2.3 2.3 epoxy compound hydrosqualene then underwent cyclization and elimination of the double bond so that the positively charged carbon atom, then these compounds will undergo further cyclization and double bonds undergo elimination to form a new hydrogen bond. Triterpenoid compounds forming.

Factors that play an important role in the biosynthesis of these compounds is sequalene and H2O. Where sequalene compounds derived from active isoprene formation from acetic acid via mevalonic acid. And the existence of groups formed hydrogen bond cyclization.

2.      Describe the structure determination of flavonoids, specificity and intensity of absorption signal by using IR and NMR spectra. Give the example of at least two different structures.

Answer :

Infrared spectroscopy is very useful for qualitative analysis (identification) of organic compounds due to the unique spectrum generated by any organic substance with structural peaks corresponding to different features. a carbonyl group, C = O, always absorb infrared light at 1670-1780 cm-1, which causes the carbonyl bond to stretch. a carbonyl group, C = O, always absorb infrared light at 1670-1780 cm-1, which causes the carbonyl bond to stretch. Cluster C = O present in the region 1820 - 1600 cm-1 (5.6 to 6.1 m). The peak is usually the strongest in the spectrum width mediun. Absorption is very characteristic. C = C has a weak absorption near 1650 cm-1 (6.1 m) high medium strong uptake in the region 1650-1450 cm-1 (6.7 m). Often indicate the presence of aromatic rings. if a compound spectrum of compound X showed absorption bands at number gelombang1455 cm-1. it can be concluded that the group-containing compound X cyclo pentane. The frequency is absorbed depends on the functional groups in molecules and molecular symmetry. IR radiation can only be absorbed by the bonds in a molecule, if the radiation has the right energy to cause vibrations of the bonds. disruption of the functional groups of contaminants will interfere with the signal curve obtained infrared spectra contain many absorption associated with the systems that interact in molecular vibrations and therefore has a unique characteristic for each molecule then the spectrum gives absorption bands are characteristic as well. Stretching absorptions usually produce stronger peaks than bending, but weakened strethcing uptake may be useful in distinguishing the same type of bond (eg aromatic substitution). IR spectra of hydroxyl-containing compounds without seeing this broad signal. broad peak of OH was replaced by a sharp signal around 3600 cm-1.

NMR spectrum which has a specific absorption systems under the influence of a magnetic field and it is not on UV-VIS and IR, the energy of electromagnetic radiation in the radio frequency region. higher sensitivity of NMR spectroscopy with increasing magnetic field strength. magnetic field homogeneity would produce wide ribbons and signal distortion. The greater the NMR spectrometer, the separation between the resonance peaks in the NMR spectrum the greater number of signals in the NMR spectrum showed the number of nuclei with different chemical environment of the molecules analyzed. Core protected effects of high (more shielded core), the core will resonate at high magnetic field strength so as to have the slide chemistry (δ) is lower than the standard compound. Notch signaling NMR spectrum will help explain to us the type of protons in a molecule, whether aromatic, aliphatic, primary, secondary, tertiary, benzyl, vinyl, asitilen, adjacent to halogen or other groups.

Spectrum IR of antochianin

  -OH group is at 3700-3100 cm -1 absorption band with a strong signal. Then the group C = O absorption is in the region 2100 cm-1 with a small enough signal. Then the group C = C absorption is shown by region 1600 cm-1 with the signal being. And group C-O is the absorption region 1080-1300 cm -1 with a small signal absorption.

Spectrum NMR of antochianin

At resonance 6-7 minutes with a very strong signal and shows a very high retention Similarly, the resonance was also detected OH group. Similarly, the resonance region 9-10 minutes have strong signal and high retention.

Spectrum IR of quercetin

-OH group is in the region of wavelength absorption 3500-3389 cm-1 with a very strong signal. Cluster C = C are in the catchment area with a wavelength of 1615-1614 cm -1. In the catchment area 1513 cm -1 indicates the presence of C = C aromatic group. And the absorption band 1243-1091 cm -1 indicate the presence of CO groups. And a catchment area with a wavelength of 807-675cm -1 indicates a CH group.

Spectrum NMR of quercetin

At resonance 6 minutes in retention 0,2 later in the resonance region is at 10 minutes retention 0,4. Furthermore, the retention of 1.4 with a signal that is at the resonance region 12 minutes. And on 20 minutes resonance with a strong signal indicating retention of 2,2.

3.       In the isolation of alkaloids, in the early stages of acid or base required conditions. Explain the basis of the use of reagents, and give examples of at least three kinds of alkaloids.

Answer :

Since alkaloids are organic compounds containing alkali similar to an alkaline nitrogen atom in the heterocyclic ring. Because it is alkaline, plants containing alkaloids serve as a base mineral to maintain ion balance.

For example, the isolation of caffeine use acid-base extraction is a type of extraction that is based on the properties of acids and bases organic compounds.
Solid liquid extraction performed an intensive process of separating caffeine from the solution. In the early stages, leaf C brewed with boiling water. This is intended to increase the solubility of caffeine in water. In this case, the temperature increase means adding heat increases the kinetic energy mix so that more easily occur dissolution. With this, it is hoped, the caffeine is extracted to achieve the optimum amount. That is the basic use of acid or alkaline reagents.

Tannins are phenolic compounds that have an OH group on the aromatic ring and is quite sour. Tannin can dissolve in water and also in dichloromethane. Because we want to extract the pure caffeine, tannin must be removed from the organic phase of this solution. In this case, we must make the tannins soluble in water and insoluble in dichloromethane dissolving more caffeine than water. The trick is to change the acidic tannins into salt (deprotonisasi-OH) that turned into a phenolic anion is not soluble in dichloromethane, but insoluble in water.

Examples of alkaloid compounds

1.      Nicotine is one of the most widely known alkaloids. This compound is an alkaloid compound with the simplest form of structure. However, the effect of its use is not as simple a form structure. As we have seen, that nicotine is the active substances contained in cigarettes and have properties quite dangerous. Nicotine will have toxic properties (poison) that are harmful if used in high enough dosis.

The isolation is :

a.       25 grams of chopped dried tobacco leaves wrapped in filter paper that has been put into the Soxhlet apparatus, extraction using 300 ml of methanol for 7 jam.sampel used is 100 grams so the extraction is done 4 times.

b.      Extract / fltrat resulting solution is evaporated until the resulting filtrate concentrated or only 10% of the original volume.

c.       Pour into a concentrated solution in the erlenmeyer flask and acidified with 2 M H2SO4 at 25 ml. The solution was stirred with a magnetic stirer to be homogeneous. The solution was tested with litmus paper to red. Then extracted with a chloroform solution of 25 ml 3 times a separating funnel.

d.      The resulting extracts were tested with the bottom layer of reagent dragendrof, if there is a positive alkaloid orange precipitate.

e.       The extract was neutralized again with NH4OH and then extracted again with chloroform 3 times.

f.       The extract obtained was evaporated to aerate, then purified by column chromatography with silica gel as the stationary phase 11.5 g, column length 10 cm, 3 cm diameter column and eluent n-hexane and chloroform, methanol with a ratio of 1:0, 7: 3, 5:5, 3:7 and 0:1 respectively 10 ml.

g.      The results of column chromatography followed by TLC with a developing solution of methanol.

h.      Extract then tested by using GC-MS, UV-Vis spectrophotometer, and IR spectrophotometers.

2.      Morphine is an alkaloid first isolated and purified from the wild. This compound is one of the alkaloids which belong to the class of drugs. This compound was isolated from opium sap and seeds, so that dependence on morphine is often referred to as addiction.

The isolation is :

3.      Caffeine is an alkaloid similar compounds belonged metilxanthine (1,3,7-trimethylxantine). Psychological effects produced can be varied and can lead to dependence. Caffeine is pretty much contained in the (30-75 mg / cup), while leaf tea also contains tannins and a small amount of chlorophyll. The structure of caffeine wake of purine ring system, which is biologically important and many of them are found in nucleic acids.

The isolation is :

Mass of three tea bags of Red Rose tea was obtained using the electronic scale. 200 g of distilled water was heated to 99 ^oC in a beaker using the hot plate. The bags were placed into the beaker and swirled for 60 seconds, at which time the three bags were removed and the liquid remaining in the bags squeezed back into the beaker using the two glass slides. The beaker was placed into the cold water bath in the large plastic container. When the temperature had reached 26 ^oC, the tea was strained using filter paper.

120 ml 6M NaOH was prepared by dissolving 28.7 g of solid NaOH into 120 ml of distilled water. This was set aside. The contents of the tea beaker were placed into the separatory funnel and allowed to settle. 20 mL of CHCl₃ was added and the funnel was inverted back and forth ten times, stopping every three times to allow gas to escape. The organic layer in the funnel was released into a new beaker. The 20 mL CHCl₃ washing was repeated twice more, each time releasing the organic layer into the second beaker. After the three washings, the contents of the separatory funnel were discarded and the contents of the second beaker were placed into the separatory funnel. Two washings with 20 mL NaOH were done, followed by one washing with 20 mL of distilled water.

Next, the contents of the separatory funnel were poured into the third beaker. This was placed over the hot plate and the temperature was set to "6". When all the liquid had evaporated, the beaker was massed on the electronic scale. Then, the white residue was scraped off the bottom of the beaker and onto a massed piece of paper. Both the clean beaker and the piece of paper with the white residue were massed. In this way, the mass of the residue was obtained in two separate ways.

4.      Describe the relationship between biosynthesis, methods of isolation and structural determination of compounds of natural ingredients. Give an example.

Answer :

Association is

if we see of understanding biosynthesis pathway is a sequence or a process in which consists of the stages of the formation of simple compounds into complex compounds. Where if you want to isolate a compound, we must know that we will compound insulation first. To obtain compounds isolated complex for our needs biosynthetic pathway, which we need in this biosynthetic enzymes and precursors in the formation of such compounds, after we obtain the complex compounds that we want, we can isolate the new compound to get a really pure mixture of other compounds or to obtain the desired pure isolates. Because the compounds derived from biosynthesis surely still mixed with other compounds that are not pure compounds. Further identification of the structure of a compound. To identify such compounds is necessary in order to yield pure compound identification of compounds obtained really large uptake purified compounds. Pure compound was obtained from the isolated and then purified. With the determination of this structure we can determine the absorbance and wavelength of each functional group of pure compounds which we derive from the isolation.

For example in the biosynthesis, isolation and structural determination of cholesterol.

Biosynthesis of Cholesterol

1. Synthesis of Mevalonate from Acetate The first stage in cholesterol biosynthesis leads to the intermediate mevalonate. Two molecules of acetyl-CoA condense, forming acetoacetyl-CoA, which condenses with a third molecule of acetyl-CoA to yield the six-carbon compound β-hydroxy-β-methylglutaryl-CoA (HMG-CoA). These first two reactions, catalyzed by thiolase and HMG-CoA synthase, respectively, are reversible and do not commit the cell to the synthesis of cholesterol or other isoprenoid compounds. The third reaction is the committed step: the reduction of HMGCoA to mevalonate, for which two molecules of NADPH each donate two electrons. HMG-CoA reductase, an integral membrane protein of the smooth endoplasmic reticulum, is the major point of regulation on the pathway to cholesterol, as we shall see. 2. ConUersion of MeUalonate to Two Activated Isoprenes In the next stage of cholesterol synthesis, three phosphate groups are transferred from three ATP molecules to mevalonate. The phosphate attached to the C-3 hydroxyl group of mevalonate in the intermediate 3-phospho-5-pyrophosphomevalonate is a good leaving group; in the next step this phosphate and the nearby carboxyl group both leave, producing a double bond in the five-carbon product, Δ3-isopentenyl pyrophosphate. This is the first of the two activated isoprenes central to cholesterol formation. Isomerization of Δ3-isopentenyl pyrophosphate yields the second activated isoprene, dimethylallyl pyrophosphate.

3. Condensation of Six ActiUated Isoprene Units to Form Squalene

Isopentenyl pyrophosphate and dimethylallyl pyrophosphate now undergo a "head-to-tail" condensation in which one pyrophosphate group is displaced and a 10-carbon chain, geranyl pyrophosphate, is formed. (The "head" is the end to which pyrophosphate is joined.) Geranyl pyrophosphate undergoes another head-to-tail condensation with isopentenyl pyrophosphate, yielding the 15-carbon intermediate farnesyl pyrophosphate. Finally, two molecules of farnesyl pyrophosphate join head to head, with the elimination of both pyrophosphate groups, forming squalene. The common names of these compounds derive from the sources from which they were first isolated. Geraniol, a component of rose oil, has the smell of geraniums, and farnesol is a scent found in the flowers of a tree, Farnese acacia. Many natural scents of plant origin are synthesized from isoprene units. Squalene, first isolated from the liver of sharks (genus Squalus), has 30 carbons, 24 in the main chain and 6 in the form of methyl group branches.

4.Conversion of Squalene to the Four-Iling Steroid Nucleus

When the squalene molecule is represented, the relationship of its linear structure to the cyclic structure of the sterols is apparent. All of the sterols have four fused rings (the steroid nucleus) and all are alcohols, with a hydroxyl group at C-3; thus the name "sterol." The action of squalene monooxygenase adds one oxygen atom from O₂ to the end of the squalene chain, forming an epoxide. This enzyme is another mixed-function oxidase (Box 20-1); NADPH reduces the other oxygen atom of O₂ to H₂O. The double bonds of the product, squalene2,3-epoxide, are positioned so that a remarkable concerted reaction can convert the linear squalene epoxide into a cyclic structure. In animal cells, this cyclization results in the formation of lanosterol, which contains the four rings characteristic of the steroid nucleus. Lanosterol is finally converted into cholesterol in a series of about 20 reactions, including the migration of some methyl groups and the removal of others. Elucidation of this extraordinary biosynthetic pathway, one of the most complex known, was accomplished by Konrad Bloch, Feodor Lynen, John Cornforth, and George Popjak in the late 1950s.

Cholesterol is the sterol characteristic of animal cells, but plants, fungi, and protists make other, closely related sterols instead of cholesterol, using the same synthetic pathway as far as squalene-2,3-epoxide. At this point the synthetic pathways diverge slightly, yielding other sterols: stigmasterol in many plants and ergosterol in fungi, for example.

Isolation and Purification of Cholesterol from Egg Yolk

Two hard boiled egg yolks were twice extracted with diethyl ether and methanol, with the filtrate collected via vacuum filtration. Potassium hydroxide pellets were added to the filtrate, the ether was distilled off, and the mixture was saponified by reflux. The crude cholesterol was isolated through a series of ether extractions and aqueous washes; then the ether was dried with MgSO4 and removed by rotary evaporation. The melting point of the yellow, sticky crude product was 91-119 oC. This crude product was then recrystallized from methanol, yielding 0.128g of pale yellow crystals with a melting point of 131-135 oC. This represents 0.33% of the original mass of the two yolks. The cholesterol was then dissolved in ether and further purified by bromination with a bromine/acetic acid reagent and debromination with zinc powder, a series of aqueous washes, and a final recrystallization from methanol. Here, a yield of 28% was recovered from an initial mass of 100 mg of recrystallized material. The melting point of the off-white crystalline final product was 146-148 oC, which is very close to the literature value for cholesterol of 148.5 oC.
From both the melting points and the physical appearances, it is apparent that the final bromination/debromination procedure did in fact further purify the product. The percent of cholesterol in egg yolks was calculated using the mass of the recrystallized product. This calculation does not seem to be valid, as the melting points demonstrated that the recrystallized product was not as pure as the final product. The goal of the experiment was accomplished; cholesterol was isolated and purified from the egg yolks.

Cholesterol identification with IR spectrum

Through the identification of the IR spectrum of this we can know that the catchment area with a wavelength of 4,000 to 2,500, known as the absorption peak group NH, CH and OH single bond. In the catchment area range 2,500 to 2,000, a triple bond absorption peak. the catchment area is the range of 2000 to 1500 as the absorption peak of the double bond C = O, C = N and C = C.