MID SEMESTER

MID SEMESTER KIMIA BAHAN ALAM

 name : Nezilia

 nim    :RSA1C110018

1.Screening of Bioactives from Marine Sources:

Fig. 2.1 Basic scheme showing the proposed workfl ow for the screening of bioactive compounds

from marine sources

 Considering the great biodiversity of marine species, the use of appropriate methodologies that can rapidly screen different marine sources for bioactive compounds is of great interest. To design this screening methodology, different parameters have to be considered. These parameters include the possible nature of the sought-after bioactive compounds (in terms of solubility, heat resistance, or molecular weight) and the bioactivity that is sought. Figure 2.1 proposes a screening methodology for the extraction and identifi cation of bioactive compounds from marine sources. Initially, a suitable extraction technique should be selected. This selection must be carried out in accordance with the predicted nature of the expected/ target bioactive compound(s). However, several extraction techniques could also be used to fully characterize the potential of the different natural sources, introducing different extraction selectivity. The use of environmentally clean advanced extraction techniques allows for the attainment of the target compound(s) of interest with more effi cient extraction procedures, while, at the same time, minimizing the use of organic toxic solvents. Depending on the extraction techniques selected, diverse extraction parameters should be tested in order to study the infl uence of solvents, temperatures, pressures, and other important parameters that might have a signifi cant infl uence on the outcome of the extraction process employed. The different extracts, obtained using diverse conditions, must then be tested for biological bioactivities by performing the appropriate functional activity assay(s). The main aim of this step is to confirm that the obtained extracts from step one possess the sought-after bioactivity.  Once the target biological activities have been confirmed, the next step involves chemical characterization of the bioactive components present in the initial extract, which may often be referred to as lead functional components (LFCs). Again, the analytical technique employed at this stage of the characterization process will depend on the nature of the initial extract or LFC in terms of its solubility, stability at different pH conditions, and heat stability, as well as the nature of the suspected bioactive

compounds. In general, advanced analytical techniques are employed, even coupled, in order to maximize the identifi cation potential. The fi nal aim of this stage of the characterization process is the correlation between the chemical composition of the LFC and the bioactivities observed. Ideally, it will be possible to identify which compounds are responsible for the observed bioactivities. It is often necessary to return to the initial extraction method employed and to perform a fi ne-tuning of this extraction procedure in order to enrich the initial extract(s) with the target compounds, which has demonstrated biological activities and has a defi ned chemical

structure.

2.The presence of compounds bibenzil very limited in nature. Because the compounds have bibenzil important biological activities, the procurement efforts of the synthesis of compounds bibenzil developed in the laboratory. Bibenzil compounds can be obtained from the catalytic hydrogenation reaction stilbena compounds. Stilbena compound composed of two benzene rings connected to each other by group C = C olefinic (alkene). Alkene compounds can be synthesized through Wittig reaction using carbonyl compounds and phosphonium Ilida. Vanillin containing carbonyl functional groups aldehydes that can be subject to Wittig reaction. Phosphonium Ilida can be made through the substitution reaction nucleophilic (SN2) of a tertiary alkyl halides with Phosphine. In the synthesis of the alkyl compounds stilbena halides can be used are benzylic alkyl halides. Vanillin can be converted into alkyl compounds benzylic halides. Vanillin first reduced with reducing agents such as LiAlH4 in THF, will vanilil alcohol derived compounds, further substitution reactions with PBr3 in CH2Cl2, will be obtained vanilil bromide compounds. Vanilil bromide when treated with triphenylphosphine be obtained phosphonium salt, which is a phosphonium salt when reacted with strong bases such as n-butyl lithium, sodium amide or sodium hydride compounds will be obtained phosphonium Ilida. Carbon negative on subsequent Ilida can attack the carbonyl group of compounds vanillin. Adduct between Ilida with vanillin was a betaine. Betaine then undergoes cyclization and elimination of triphenylphosphine, and will get stilbena substituted compounds. When stilbena substituted compounds are catalytic hydrogenation reactions, you will get a compound bibenzil.

3. The rules in choosing a solvent for the isolation and purification of compounds of natural materials:
a. The solvent should have a high solubility and chemical solvents used are not hazardous or toxic.
b. Neutral, non-volatile and non-flammable, and does not affect the selective nutritious substances.
c. The solvent should be able to dissolve the reactants and reagents.

d. The solvent should have a boiling point right.

e. According to the nature of the compound to be isolated, polar or nonpolar.

f. Cheap and easy to obtain

g. Solvent does not react with the solute

h. The solvent should be easily removed at the end of the reaction.

-Isolation terpenoid compounds in the leaves of patchouli plants using solvents n-hexane and methanol.

-the flavonoids can be extracted with CH2Cl2, CHCl3, ether, EtOAc.

-to isolate the medicinally important alkaloids an acid solution, converted back into the free bases, and taken into another water-insoluble organic solvent (eg benzene) to give, after evaporation, the crude alkaloid extract.

-Steroids are isolated from natural sources by extraction with organic solvents, in roomates Usually they dissolve more readily than in the aqueous fluids of tissues. Often the source material is treated initially with an alcoholic solvent, roomates dehydrates it, denatures (renders insoluble) proteins associated with the steroids, and dissolves many steroids. Saponification either of whole tissues or of substances extracted from them by alcohol splits the molecules of sterol esters, triglycerides.

4. IR spectroscopy

Infrared spectrophotometry is used to identify a compound with group functions. For the purpose of structure elucidation, the wavenumber region 1400 - 4000 cm-1 which is at the left of the IR spectrum, an area that is particularly useful for the identification of functional groups, which is the absorption of the stretching vibration. Furthermore, the area just to the right of wave numbers 1400 cm-1 are often very complicated because in this region occurred absorption of stretching vibration and bending vibration, but any organic compound having a Characteristic absorption in this region. It is therefore part of the spectrum is called fingerprint region (fingerprint region). Currently there are two kinds of instruments, namely IR and FTIR spectroscopy (Furier Transformation Infra Red). FTIR is more sensitive and accurate example to distinguish cis and trans forms, conjugated and isolated double bonds and others are in indistinguishable IR spectrophotometer.