Comparación de extractos de propóleos ecuatorianos producidos por apis mellifera mediante cromatografía en capa delgada

Abstract

Propolis is a bee product composed of wax and vegetable exudates, mostly produced by bee species such as Apis Mellifera. According to the literature, it presents a remarkable chemical variability due to its botanical origin, which makes it a relevant subject of study. In Ecuador, this research is of special interest, since compounds have been identified in national propolis that are not found in those of other countries, due to the plant biodiversity of Ecuador. From a social and economic perspective, the need arose to implement accessible methods for the differentiation of propolis extracts, being thin layer chromatography (TLC) a viable alternative to more sophisticated but less accessible techniques. In this study, a TLC-based procedure was developed for the differentiation of Ecuadorian propolis extracts produced by Apis mellifera, applying different chromatographic conditions. The research followed a quasi-experimental and retrospective design, using representative samples of Ecuadorian propolis previously studied by high-performance liquid chromatography (HPLC), whose data complemented the analysis. Silica gel plates were used with fluorescent indicator (254 nm) on aluminum support and different developers such as: ultraviolet light (254 and 365 nm), sulfuric acid/vainillin/heat, ammonia, FeCl3, iodine and KMnO4 in basic medium. The analysis was complemented by comparison with 14 reference substances and confirmation of results by preparative TLC and HPLC-DAD. In addition, the antimicrobial activity of propolis extracts was evaluated by the Kirby-Bauer method. The results revealed that two mobile phases provided the best chromatographic separations. We were able to differentiate different propolis samples: sample P19 (Group I) showed matches with chrysin and CAPE in different physical and chemical revelations, which was confirmed by preparative TLC and HPLC-DAD. A similar procedure was performed on samples P20 (Group IV) and P5 (Group V), where the presence of sterbin and nemorosone, respectively, was demonstrated. In contrast, samples P6 (Group II) and P4 (Group III) showed similarities between them but could be differentiated taking into account the position of the most intense spots in the chromatograms. Sample P8, rich in triterpenes, could also be differentiated from the rest. As for the antimicrobial activity, the extracts did not show activity against S, aureus and E. Coli with the amounts evaluated. This study highlights the usefulness of TLC as an accessible technique for the differentiation of Ecuadorian propolis and opens the possibility of future research, such as the exploration with other reference substances that allow a more detailed characterization of the samples.