SEMESTER EXAM

Question

1. Explain the triterpenoid biosynthetic pathway, identify important factors that determine the quantities               produced many triterpenoids!
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!
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!
4. Explain the relationship between biosynthesis, methods of isolation and structural determination of compounds of natural ingredients. Give an example!

Answer

1. Biosynthesis of Triterpenoid

In general, the biosynthesis of terpenoids three basic reactions, namely:

• The establishment of active isoprene derived from acetic acid via mevalonic acid.
• Merging head and tail isoprene units to form mono-, seskui-, di-, Sester-, and poly-terpenoids.
• Merger tail and the tail of the unit C-15 or C-20 produces triterpenoids and steroids.

Activated acetic acid coenzyme A did produce acid asetoasetat Claisen condensation. The resulting compound is then reacted with acetyl coenzyme A did aldol condensation produces branched carbon chains as found in mevalonic acid. The reactions that followed was phosphorylated, elimination of phosphoric acid and subsequent decarboxylation produces IPP to DMAPP by the enzyme berisomerisasi isomerase. IPP as active isoprene units joined head to-tail with DMAPP and this merger is the first step of the polymerization of isoprene to produce terpenoids. This merger occurs because electrons attack the double bond carbon atoms of IPP to DMAPP a shortage of electrons followed by removal of pyrophosphate ions.

Knowledge triterpenoid biosynthetic pathways (terpenoid) allows for modification of metabolites that can be produced in greater numbers and in a shorter period of time, knowing the structure of the resulting metabolites, and then to do the synthesis to produce its derivatives. Modifications can be done in several ways, namely:

• Blocking the path to optimize the other lane. For example, inhibition of acetate-mevalonic pathway in the formation of isoprene to increase the production of isoprene on track trioses-pyruvate.
• The addition of enzymes, precursors, intermediates, or substrate (enzyme activation). The addition of these substances in the biosynthesis of measures appropriate to increase the production of metabolites. For example, the addition squalen on cell suspension cultures of neem as a precursor to the formation of azadirachtin azadirachtin done when production increases. So that needs to be made the growth curve (Zakiyah, Zulfa, et al, 2003).
• Modification of environmental growth conditions. Certain conditions can trigger cells to produce a metabolite. Based on the hypothesis that believed all along that plant secondary metabolites formed in a depressed condition, as a function of secondary metabolites is as a form of a plant response to environmental conditions to sustain life.

2. NMR SPECTRUM

NMR is used to determine the structure of natural and synthetic components are new, the purity of the components, and the direction of chemical reactions in solution as well as the relationship of components that can undergo chemical reactions. NMR spectroscopy is a tool developed in structural biology. NMR in biology melekuler performed on the sample in the form of a solution to prior purification or extraction. Can be determined by NMR molecular structure and the changes that occur when receiving interference from outside (stimulus, disease or the addition of other substances).

nmr spectrum of flavone

nmr spectrum of quercetin

Identification by 1H NMR spectra showed the presence of five aromatic protons, hydroxyl proton, five aliphatic protons and 3 methyl protons. Based on these data showed a compound of flavonoids (quercetin), which binds to a sugar group is rhamnosil. Based on data from HMBC, rhamnosil bound to C-3 of quercetin. These compounds are known as quercetrin (quercetin-3-O-rhamnosida).

IR SPECTRUM

IR spectroscopic used to determine the functional groups. This may be due to the infrared spectra of organic compounds are typically organic, meaning its compounds will have different spectra. The use of infrared spectra in organic chemistry using the local wavenumber range 666-4000 cm-1. When the compound is passed through the infrared organic compounds, some frequencies are absorbed and others will continue. Infrared spectroscopic used to determine the structural information of organic compounds.

IR spectrum of Rimpang temu ireng

Based on the figure can be seen in the strong bands at 1714.6 cm-1 are specific to carbonyl groups. Uptake sharp 1261.4 and 1217.0 cm-1 arises from the conjugated CO group vibrations. Ribbon at 1091.6 and 1029.9 cm-1 is the absorption of the methoxy group. Ribbon at 3020.3 cm-1 comes from the = CH str supported by bands between 1600 cm-1 and 1500 cm-1 indicates the presence of an aromatic nucleus. Small bands namely weak 1652.9 cm-1 coming from the vinyl. The ribbon on the area under the 3000 cm-1 and reinforced by bands around 1450 cm-1 indicates the presence of alkyl methylene. Based on the above analysis of the IR spectrum, it can be concluded that the compounds contained aromatic group, C = O, CO, vinyl,-CH2-and methoxy.

IR spectrum of Quercetin

IR spectra of quercetrin shows the functional groups OH (3294 cm-1), CC aliphatic (2931 cm-1), C = O (1728 cm-1), C = C aromatic (1504 and 1604 cm-1) and COC ether (1064 cm-1). 13C NMR spectra showed 14 carbon aromatic, one carbonyl, and six aliphatic carbon.

3. Effectively insulating compound of natural ingredients then the selection of organic solvent to be used should be appropriate to the nature of the compound to be isolated, which will be easier to polar solvents dissolve polar compounds and otherwise non-polar compounds more soluble in non-polar solvents (Harborne, 1987).

Alkaloids are usually isolated from the plant by using the method of extraction. Solvents are used when extracting the compound mixture is acidified water molecules. This solvent will be able to dissolve the alkaloid salts, this method has been used to extract ergotamine from ergot fungus ..

Moreover, it can also alkalinize alkaloid-containing plant material by adding sodium carbonate. Bases are formed can then be extracted with an organic solvent such as chloroform or ether, it has been used to mengektraksi alkaloid compounds found in plant seeds of mahogany (Swietenia mahogany Jacq).

For alkaloids that are not heat resistant, insulation can be done using techniques alkalinize the solution concentration by first. By using this technique it will evaporate and hereinafter alkaloids can be purified. Usually used for the purification of the compound nicotine. As for the solution of the alkaloid in water that is acidic, then the solution must basified beforehand. Further alkaloids can be extracted using an organic solvent.

4. Biosynthesis, isolation and structural determination of the method of natural materials closely related compounds. By knowing the process of biosynthesis of a compound of natural materials, it will be known process / chemical reactions that occur in obtaining the desired compound. Then, to obtain the pure compound isolation process is carried out to obtain the compound of natural ingredients required / chill. In isolation, the structure can be determined. Thus, from the results of the determination of the structure can be compared with the structure of chemical compounds produced in the process of biosynthesis to match the structure.

Once known molecular structure is usually followed by a modification of the structure to obtain compounds with the desired activity and stability. Besides, with advances in biotechnology, can also be done to improve the quality of plants or organisms through tissue culture or the creation of a transgenic plant would also produce various kinds of new secondary metabolites of diverse and possibly with a different molecular structure to that found from plants initially. Thus the research opportunities in the field of natural products is also not limited. So the secondary metabolite compounds can be used for the benefit of human life.

Example is in the 1700s, chemists examine the myths that circulate in the community about the benefits of tea to stay young. Once the research is done by experts who know the biosynthesis of tea contains a variety of compounds. Then the experts to obtain the isolated compounds contained in tea. After the isolation, the experts identified strukutr compound, determining the structure of these experts know that tea contains flavonoids that are useful as antioxidants to prevent free radicals that enter the body. One is to prevent cancer and many more benefits.