The aim of this study was to determine the chemical variability of Allamanda cathartica flowers collected in different localities of Santa Catarina State, Brazil. Extractive solutions (25 samples) were analyzed by HPLC-DAD for the qualitative and quantitative profiles of the iridoid plumieride, the flavonoid rutin as well as total flavonoid content expressed in rutin. The chemical variability was evaluated by Principal Component Analysis (PCA) and Hierarchical Clustering Analysis (HCA). The samples demonstrated similar chromatographic profiles. In PCA analysis, Araquari samples AC01, AC08 and AC25 did not group with other samples obtained from other locations. In the HCA analysis, it was possible to observe hierarchially similar groups, generating 5 clusters. Group 5 (samples AC01, AC08 and AC25) presented lower similarity compared to the other groups. This dissimilarity can be explained by the amount of metabolites from each collection. Regarding the content of markers, it was observed a variation between 27 to 230 mg/g, 2.7 to 9.5 mg/g and 7.14 to 17.8 mg/g for plumieride, rutin, and total flavonoids, respectively. The samples from Araquari (AC01, AC08, AC25) presented the highest concentrations of chemical markers. Therefore, for reproducibility and standardization of A. cathartica flower extracts, it is important to determine the location and the plant cultivation conditions.

A simple and efficient microwave-assisted extraction process has been developed in order to extract plumieride from Allamanda cathartica flowers. The extracts have been obtained through microwave-assisted extraction (MAE) process with ethanol and ethyl acetate at different time, power and temperatures. Static maceration at room temperature with ethanol and ethyl acetate was obtained in order to compare the efficiency of extraction. HPLC method was validated to quantify plumieride in the extracts. The analyzed parameters: linearity (R2 = 0.999), precision (CV 3.3%), recovery (98%), specificity (97%), limit of detection (1 µg mL-1), and limit of quantification (2 µg mL-1) were satisfactory. The yield of plumieride reached 43% in the extracts under the optimal MAE conditions (10 min, 300W). Plumieride recoveries by conventional extraction method were 12% with ethanol and 22% with ethyl acetate. Time and power parameters on plumieride extraction yield was determined by applying a factorial design and surface plots. Ethanol was the best extractor solvent and it was possible to obtain high contents (52 mg g-1 of dry flowers) at optimized conditions. It can be concluded that MAE process has actual advantages over the conventional extraction method in terms of shorter time and higher efficiency to recover plumieride from A. cathartica flowers.