Analytical method development, validation and forced degradation studies for rutin, quercetin, curcumin, and piperine...

Curcumin, rutin, and quercetin are well-known flavonoids and piperine is an alkaloid, commonly used as spices and traditionally used to treat a variety of conditions. In the current scenario, the stability problems of phytoconstituents are a major problem for regulators and because of the complex nature of the components of plant extracts.

A simple, fast, and sensitive ultra-force reverse phase liquid chromatography (RP-UFLC) has been developed, validated, and studied for degradation studies.

Seven different plant extracts were quantified and the stability of the constituents was estimated by forced degradation studies. The separation of the phytoconstituents was performed on a Phenomenex C₁₈ column with a mobile phase of 80% acetonitrile and 20% (25 mM) ammonium acetate (pH 3) at a flow rate of 1 mL min^-1 detected at 380 nm.

The results of the study showed that the method developed was linear with a range of correlation coefficient 0.994-0.999. The specificity, precision, and accuracy were well within the limits. Quantification showed that a maximum content of curcumin (3.61%, w/w) was found in the extract of Curcuma longa L extract, piperine in Piper nigrum L (13.92%, w/w), rutin in Glycyrrhiza glabra L (15.19%, w/w), and quercetin in Camellia sinensis L (0.36%, w/w). Forced degradation studies have shown that rutin was very stable in acidic media (6.65%, w/w) and curcumin was less stable in alkaline media (100%, w/w).

The method developed was simple, fast, accurate, sensitive, and applicable for the determination of phytoconstituents in natural extracts and herbal formulations, individually or in combination and can be used as a quality control tool.