Quantitative Determination of Piperine. I. The Komarowsky Reaction

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Abstract
SUMMARY: A highly stable reagent consisting of para‐dimethylaminobenzaldehyde (I) or para‐hydroxybenzaldehyde (II) or other cylic aldehydes, plus thioureau in concentrated sulfuric acid, has been developed for use in determining piperine. The slightly yellow reagent, if stored under refrigeration in a brown bottle, maintains a constant chromogenic capacity for 4–6 weeks. Piperine when heated with this reagent for 15 min at 100°C develops a red color (I max. 490 mp) or purple color (II max. 570 mμ) whose intensity is proportional to the amount of piperine present. Water inhibits color development, but a small amount of methyl alcohol is necessary. Ethyl alcohol cannot be used, since it develops color with the reagent. Critical factors for reproducible, quantitative assay are the concentration of acid and thiourea in the reagent and the time and temperature of heating the reaction mixture. For I, the most sensitive of the aldehydes used, good precision, with a standard deviation of it ± 3470, was attained. Between the levels of 0.01 and 0.06μM of piperine per ml of reagent, there is a linear relation which may be described by the least‐squares equation.X = 0.088 Y + 0.00175 where X = concentration (μM) of piperine per ml of reagent Y = absorbance at 490 μM Percent piperine in sample = X (0.28533) (dilution factor)′ 100 Sample weight (mg)