| The future needs of the US botanical market include a sustainable supply of high quality raw material, and a reliance on scientifically evaluated products. This research was conducted as a series of projects designed to investigate and accurately quantify the chemical variability of raw material in response to water stress, developmental stage, time of harvest, organ, and to evaluate relationships between bioactive compounds, through the development and use of robust analytical methods for purple coneflower (Echinacea purpurea (L.) Moench) and St. John's wort (Hypericum perforatum L.). Purple coneflower plants subjected to brief water stress periods over two seasons produced fall-harvested roots with significantly greater chicoric acid concentration and yield than corresponding well-watered controls. St. John's wort plants subjected to water stress during both flower and seed development periods exhibited significantly increased combined flower concentrations of flavonoids (rutin, hyperoside, isoquercitrin, quercitrin and quercetin; mean increase of 14%) as compared to control plants that received adequate water. However, water stress decreased individual flower chemical yields of an measured compounds, due to the significant decrease in flower dry weight of the water-stressed plants. Many St. John's wort dietary supplements are produced to specified levels of either the hypericins or hyperforins. The data showed that the use of these compounds alone were not adequate to ensure equivalent quality based on their relationships to other biologically active compounds. Purple coneflower dietary supplements are generally produced to specified levels of phenolics and/or alkamides. The data showed that the use of chicoric acid alone, for individual organs and mixed-organ samples, explained an average of 75% and 87% of the variation, respectively, of the combined concentrations of chlorogenic acid and caftaric acid. While the use of HPLC remains the most powerful and flexible tool for chemical quantification of bioactive plant compounds, near infrared reflectance spectroscopy (NIR) is a rapid, non-destructive method that does not require extensive sample preparation or the use of chemical solvents. The results showed that NIR has the potential to quantify natural products such as chicoric acid in root samples of E. purpurea, producing coefficients of determination for calibration of 0.90. |
