Isolation of Piperine from Black Peppercorns

The exercise made use of freshly ground black peppercorns to yield a consistent and reliable results for the piperine content of the sample. Old or aged black peppercorns loose their pungent taste. And it was mentioned that, piperine is responsible for this pungent, or hot, taste of peppers. Thus, old peppercorns are not reliable to be used.

The Reflux technique allows the solution to be boiled and the vapors are condensed that allows the return of the condensate to the reaction flask. It was already known that boiling, an increase in temperature, increases the solublitiy of compounds in a solvent. The organic compounds, including the sought-for piperine, was dissolved in the organic solvent upon boiling of the solution. During reflux, the loss of the solvent containing those organic compounds was minimized.

The filtrate from the reaction mixture (from reflux) undergone distillation for further purification. Distillation allows the partial vaporization of the solvent, or liquid, and allowing it to be condensed in a different portion of the apparatus. The distillate collected is the "recovered ethanol", which was used as the solvent in the earlier part of the exercise.

The pot residue left in the distilling flask was washed with 95% ethanol to collect most of the residue in the flask. The addition of ethanolic KOH to keep the acidic material in solution and it could increase the rate of crystallization upon cooling to room temp. This treatment would yield piperic acid and piperidine (responsible for the peppery odor). After which, water is added to the solution to displace the ethanolic KOH from being a solvent becaue EtKOH is more soluble in water while piperine, and its other froms, are not. Thus, it yielded a metallic yellow precipate which is identified as crude piperine.

The crude piperine is dissolved in minimum amounts of acetone for recrystallization. piperic acid would react with acetone yielding purified piperine as the final product.It could be concluded that piperidine may have been removed by the addition of acetone because of the lesser peppery odor.

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Research say that pepper contains 5-9% alkaloid piperine, 1-2.5% vegetative oil, 6% pungent resin, 30% piperidine and starch. The usual purified piperine from piper nigrum is 3-9% on dry weight basis. And the calculated percentage yield for the purified piperine is 3.19%, which is still part of the ideal range of piperine content. As for the crude piperine, it resulted to a higher percentage yield (5.29%) because it's crude. And Crude contains contamination and other substances other than the sought-for organic compund.

The characterization of piperine involved the use of the melting point determination. Melting point, in solids, is the temperature at which the solid and liquid are in equilibrium at a total pressure of 1 atmosphere. It also defines the purity, and serves as identification and characterization of the sample. When a sample is pure, the temperature remains constant during the whole process of solidification. And that temperature is the melting point of the substance being analyzed.

The Oil bath method (see fig2.6 for the set-up) is most often used in melting oint determination. Only a few crystals of the substances is needed to identify its melting point. It must be kept in mind that the thermometer and the sample must be at the same temp while the sample melts, and so is the heating as the mP is approached should be slow. Melting point ranges happen when there is a little rise in the temperature as thesamle is melting. Prescence of impurities could also cause the melting of the asmple over a range of temperature.

Another method if the use of the fisher-johns melting point apparatus. Here, the sample and the thermometer are both supported by an electrically heated metal block. The apparatus contains a magnifying glass for a closer observation of the melting of the sample.

In oil bath method, results say that our recovered sample has the MP range of 85-128. This range could have been cost by the use of a filter paper prior to MP determination. FP contains cellulose that could cause contamination of the purified sample since powdered sample is used so it could fit the capillary tube. On the other hand, fisher-johns apparatus identified a very sharp MP of the the sample, 131C. this could have been cause by the use of the needle-like crystals whch did not come too much in contact with the filter paper. Thus, less contamination was observed.

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