Cosmos caudatus is a traditional medicinal plant from the family Compositae. It is known in Malaysia as Ulam Raja which
means the king’s salad. The fresh leaves are consumed as appetizer for health benefits for various ailments such as to improve
blood circulation and to promote the formation of healthy bones. This study aims to develop a reverse phase HPLC method for
quantification of rutin, quercitrin and quercetin as the marker compounds in fifteen different Cosmos caudatus extracts. The method
was validated for selectivity, linearity, precision, accuracy and limits of detection and quantification. Selectivity was confirmed
based on retention time and UV-Vis spectra; linearity was in the range 0.5-500 μg/ml at R2=1.0; the intraday and interday
precision was determined as the relative standard deviation of peak area and retention time, and was found to be 0.3±0.07% and
0.02±0.004%, respectively; percentage recovery of rutin, quercitrin and quercetin was in the range (91.63±3.1)%–
(95.93±3.0)%, (80.41±1.5)%–(93.99±5.0)%, and (92.84±3.1)%–(98.05±2.6)%; the limits of detection were in the range 0.048-
0.052 μg/ml, 0.144-0.157 μg/ml, 0.078-0.079 μg/ml, and the limits of quantification were 0.235-0.236 μg/ml, 0.152-0.164
μg/ml, and 0.461-0.497 μg/ml, respectively. Results showed Cosmos caudatus contains high concentration of flavonoids and
flavonoid glycosides including rutin, quercitrin, iso-quercitrin and quercetin and quercitrin being the major constituent in this plant.
Hence it may be used as a reference compound for standardization of this medicinal herb. In conclusion, the method developed can
be used for quantitative analysis in quality control, stability studies, pharmacokinetics, and standardization purpose.