UJIAN AKHIR SEMESTER

MATA KULIAH       : KIMIA BAHAN ALAM

SKS                             : 2

DOSEN                      : Dr. Syamsurizal, M.Si

WAKTU                     : 22-29 Desember 2012

PETUNJUK : Ujian ini open book. Tapi tidak diizinkan mencontek, bilamana ditemukan, maka anda dinyatakan GAGAL. Jawaban anda diposting di bolg masing-masing.

1.Jelaskan dalam jalur biosintesis triterpenoid, identifikasilah faktor-faktor penting yang sangat menentukan dihasilkannya triterpenoid dalam kuantitas yang banyak.

2.       Jelaskan dalam penentuan struktur flavonoid, kekhasan signal dan intensitas serapan dengan menggunakan spektrum IR dan NMR. Berikan dengan contoh sekurang-kurangnya dua struktur yang berbeda.

3.      Dalam isolasi alkaloid, pada tahap awal dibutuhkan kondisi asam atau basa. Jelaskan dasar penggunaan reagen tersebut, dan berikan contohnya sekurang-kurangnya tiga macam alkaloid.

4.      Jelaskan keterkaitan diantara biosintesis, metode isolasi dan penentuan struktur senyawa bahan alam . Berikan contohnya.

ANSWER

1.      Squalen Biosynthesis reaction (Making Triterpenoid)

Path begins at biosentesis triterpenoid acetyl coenzyme A did kodensasi type aldol produce a branched carbon chains which are found in mevalinat acid and subsequent reaction such as phosphorylation reactions, elimination of phosphoric acid and decarboxylation yield piroposfat isopentenyl (IPP) which selanjutnyaa berisomerisasi a dimethyl allyl pyrophosphate (DMAPP) by enzyme isomerase.

IPP which are the units of active isopern DMAPP join between the head and tail of this is caused by the attack of electrons of the double bond carbon atoms of IPP to DMAPP a shortage of electrons followed by the removal of phosphate ions produced piro geranil. after it is formed aqualane triterpenoids which experience structuring as shown below:

a.      EC 2.5.1.21 squalene synthase: Reaction: 2 (2E,6E)-farnesyl diphosphate + NAD(P)H + H+ = squalene + 2 diphosphate + NAD(P)+ (overall reaction) (1a) 2 (2E,6E)-farnesyl diphosphate = diphosphate + presqualene diphosphate (1b) presqualene diphosphate + NAD(P)H + H+ = squalene + diphosphate + NAD(P)+

This microsomal enzyme catalyses the first committed step in the biosynthesis of sterols. The enzyme from yeast requires either Mg2+ or Mn2+ for activity. In the absence of NAD(P)H, presqualene diphosphate (PSPP) is accumulated. When NAD(P)H is present, presqualene diphosphate does not dissociate from the enzyme during the synthesis of squalene from farnesyl diphosphate (FPP) [8]. High concentrations of FPP inhibit the production of squalene but not of PSPP

b.      EC 2.5.1.32 : geranylgeranyl diphosphate = 15-cis-phytoene + 2 diphosphate (overall reaction)

(1a) 2 geranylgeranyl diphosphate = diphosphate + prephytoene diphosphate

(1b) prephytoene diphosphate = 15-cis-phytoene + diphosphate

Requires Mn2+ for activity. The enzyme produces 15-cis-phytoene. cf. EC 2.5.1.99, 15-trans-phytoene synthase.

Enzymatic cyclization reactions

Enzymatic cyclization with the Help of Enzymes. Initiation cyclization by oxygen Molekuler.Simbol E-O2 * is used to represent oxygen "activated" by forming a complex with the enzyme.

biosynthesis Lanosterol

Sumber http://dc314.4shared.com/doc/5KpoKJFS/preview.html

factors that influence the scope of the results of triterpenoids is a method of isolation of factor where many existing methods of isolation. to produce triterpenoids, which method of isolation is an important factor to generate the numbers or results of triterpenoids same. one of the many methods that produce triterpenoids are Soxhlet extraction method, which is a method of immersion and heating causes pressure differences lead to breakage of the wall and the cell membrane of heating causing evaporation and condensation occurs after passing the air conditioner so that the steam is attached to the pipe wall and serkulasi occurred, repeated movement that causes the result of extract much triterpenoid.

2.      Determination of flavonol Substituents at the core is done by measuring the spectrum at a wavelength of 200-600 nm. Flavonoids shows typical spectra in the region, consists of two peaks, which is in the range of 240-285 nm (bands II) and 300-550 nm (tape I).

IR spectrum of quercetrin demonstrate 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. Then the identification of the 1 H 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).

http://digilib.uns.ac.id/pengguna.php?mn=showview&id=13616

Isoflavon

Antosianin

3.      In the acid extraction, the plant material is processed by the solution of a weak acid (eg acetic acid in water, ethanol, methanol, or). Bases is then added to convert alkaloids to basic forms are extracted with an organic solvent (if the extraction is done by alcohol, will be removed first, and the remainder is dissolved in water). Solvents are used when extracting the compound mixture is acidified water molecules. This solvent will be able to dissolve the alkaloid salts. It also can basify alkaloid-containing plant material by adding sodium carbonate. Bases are formed can then extract with organic solvents such as chloroform or ether

As for the solution of the alkaloid in the acidic water then the solution must basified beforehand. Further alkaloids can be extracted using organic solvents.  Another way to get the alkaloids from the alkaline solution is the method using a reagent penjerapan Lloyd. Alkaloid that is obtained is then eluted and precipitated using reagents Meyer. After that, the precipitate formed is separated by ion exchange chromatography method.

Grinding done to break down the cell walls of secondary metabolites botanicals that, in this case aalah alkaloids, can come out. Chloroform is used to pull the alkaloid bases. Dragendorff reagent and Mayer's reagent is a common reagent used for the identification of alkaloids. Acid HCl (1:10) in water is used to turn into salt alkaloid base is drawn back into alkaloid HCl chloroform. Due to attract alkaloid bases used chloroform is semipolar, it can be concluded that the alkaloid compounds is semipolar.

Example:
a) Purification Nicotine compounds, to alkaloids that are not heat resistant, insulation can be done using the technique of concentration by basify the solution first. By using this technique the alkaloid will evaporate and then be purified by steam distillation method.
b) Purification of morphine, an alkaloid morphine binds organicmisal acid binds with acetic acid to form acetic acid. Because it's time to identify, ammonia is used to free the alkaloid from organic acids and alkaloids make alkaline soluble in chloroform.
c) sample extract caffeine drip in holes 1 plate was tested by adding 1-2 drops of reagent meyer and allowed to settle. After that, the observed precipitation and its color. Sample extract caffeine in the 2 hole plate drops tested by adding 1-2 drops of reagent dragendroff and allowed to settle. After that, the observed precipitation and its color.

4.      Relationship between the biosynthesis, isolation and structural determination of compounds of natural ingredients are: Isolation role in the process by which we can get the pure compound (natural materials) of plants. then identified the elements of the pure compounds obtained by spectroscopic methods, followed by testing the biological activity of either crude extract or pure compound. Once known molecular structure is usually followed by a modification of the structure through the process of biosynthesis to obtain compounds with the desired activity and stability.