Percorrer por autor "Pereyra, A."
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- Assessing the performance of analytical methods for propolis – A collaborative trial by the international honey commissionPublication . Vilas-Boas, Miguel; Lopes, Mélissa; Nunes, Luís; Pereyra, A.; Kunert, C.; Beckh, G.; Çelemli, Ömür Gençay; Sorkun, Kadriye; Georgé, Stéphane; Paulo, Luísa; Gardini, Silvia; Sancho, M.Teresa; Osés, Sandra María; Fernandez Muiño, Miguel Angel; Bankova, Vassya; Popova, Milena Petkova; Trusheva, Boryana S.; Petrov, N.; Dastan, T.; Tananaki, Chrysoula H.; Falcão, SoraiaPropolis is a resinous beehive product with extraordinary bioactivity and chemical richness, linked with the botanical sources of the resin. The potential of this product keeps captivating the scientific community, conducting to continuous and growing research on plant sources, composition, or applications in agriculture, cosmetics, pharmacy, odontology, etc. In all cases, the quality assessment is a requirement and relies on methods to extract the bioactive substances from the raw propolis and quantify different components. Unfortunately, besides the absence of international quality requirements, there is also a lack of standardized analytical procedures, despite the presence of several methodologies with unknown reliability, often not comparable. To overcome the current status, the International Honey Commission established an inter-laboratory study, with propolis samples from around the globe, to harmonize analytical methods and evaluate their accuracy. A common set of protocols was matched between twelve laboratories from nine countries, for quantification of ash, wax, and balsamic content in raw propolis, and spectrophotometric evaluation of total phenolics, flavone/flavonol, and flavanone/ dihydroflavonol in the extract. A total of 3428 results (97% valid data), were used to assess the methods’ accuracy following ISO-5725 guidelines. The within-laboratory precision, revealed good agreement levels for the majority of the methods, with relative variance below 5%. As expected, the between-laboratory variance increased, but, with exception of the flavanone method that revealed a clear lack of consistency, all the others maintained acceptable variability levels, below 30%. Because the performance of ultrasounds procedures was low, they cannot be recommended until further improvements are made.
- A collaborative study for the performance evaluation of analytical methods for própolis. An IHC trialPublication . Lopes, Mélissa; Pereyra, A.; Beckh, G.; Schreiter, H.; Çelemli, Ömür Gençay; Sorkun, K.; Georgé, Stéphane; Paulo, L.; Sancho, M.; Bankova, Vassya; Dastan, T.; Tanaki, C.; Nunes, Luís; Vilas-Boas, MiguelPropolis is well known for its potential applications but also for its chemical complexity, making it very hard to define quality standards for its commercialization. Every day it is possible to find new publications on this bee product describing a new singularity, a particular substance with high bioactivity never described or a new application. This systematic increment in scientific information, although relevant, do not always enable a clear comparison between samples due to the different methods and procedures used to assess its quality parameters. To strength the scientific studies on propolis and establish a background for future definition of standards for industry, producers and laboratories, the Propolis Working group of the International Honey Commission, performed an interlaboratory study to harmonize basic analytical methods and evaluate their accuracy and robustness. The collaborative study was accomplished by 12 laboratories from 9 countries and a company experienced in propolis trade. The samples under analysis, representing fifteen different origins around the globe, where fractionated and distributed to each laboratory, and so all participants analysed the same material. Overall, six parameters were evaluated: ashes, wax and balsamic extract on raw propolis, and total-phenolics, flavones and flavanones on propolis extract. The results were analysed following the international guidelines ISO 57251. Outliers were removed using Cochran’s test, to check the homogeneity of variances at certain levels, and Grubb test’s, to check the consistency of the laboratories average. The results revealed good reproducibility for ash, wax, balsamic content and flavones, while for flavanones the method is clearly unsuitable.