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A fast isocratic HPLC method for analysis of steviol glycosides from Stevia rebaudiana leaves was developed with a high selectivity for nine known steviol glycosides and low eluent consumption. The analytical method was performed on a Purospher Ò STAR RP-18 endcapped 3 lm Hibar Ò RT 250-4.6 column at 50°C with an eluent composition of water (65 vol. %) and acetonitrile (35 vol. %). With a flow rate of 1 mL min -1 , nine known steviol glycosides were detected selectively after 15 min. Method validation for rebaudioside A showed a LOD of 0.0004 mg mL -1 and a LOQ of 0.0038 mg mL -1 . Particularly with regard to moderate solubility, the method is linear up to a concentration of rebaudioside A of 4.8 mg mL -1 . The linear calibration curve was obtained with a coefficient of determination of 0.9997 ± 0.0002 and a total error of 2.01 % RSD (n = 12). The accuracy of the method was determined by the percentage mean recovery rate to 100.99 ± 2.01 %. The intra-day precision was in a range of 0.12 to 1.96 % RSD and the inter-day precision varies from 0.02 to 1.89 % RSD. Small changes in operating conditions like eluent composition (65 ± 2 vol. %), temperature (50 ± 10°C) or flow rate (1 ± 0.2 mL min -1 ) do not affect the performance of the analytical method. The reliable and robust proposed HPLC method can be applied for quantification of steviol glycosides in Stevia rebaudiana Bertoni leaves in laboratories and quality control in industry.

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The standard procedure for the selection of solvents for natural plant extraction is a hybrid approach of solubility estimation and experimental investigations to reduce the time of solvent screening to a minimum. The focus is on the selection of a suitable solvent for natural product extraction in the early stages of process development when thermodynamic data are not yet available and solid‐liquid extraction is still an alternative to other techniques. The standard procedure is implemented in Microsoft® Excel™, provides the necessary information, creates experimental test plans, performs calculations and supports the user by structured descriptions to select the most desirable solvent for extraction. In this study, its application to the natural products rebaudioside A from Stevia rebaudiana Bertoni leaves, caffeine from guaraná seeds, and artemisinin from Artemisia annua leaves is demonstrated. The standard procedure predicted solvents that were found in the literature, plus solvents with even better extraction performance than the ones described in the literature.

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