PHYSICOCHEMICAL PROPERTIES, PHENOLIC COMPOSITION AND ANTIOXIDANT EVALUATION OF GEOPROPOLIS EXTRACTS FROM AMAZONIAN STINGLESS BEES

Stingless bees of the Meliponini tribe mix plants resins with wax and soil particles to produce geopropolis, producing a material that has antioxidant activity, anti-inflammatory and antimicrobial properties. These products may contribute to bioeconomic development of meliponiculture in the Amazon region. However, it is often discarded due to the presence of soil particles and lack of specific official quality standards. This study aimed to investigate the physicochemical properties of geopropolis from Melipona interrupta collected in the city Manaus, Amazonas, Brazil and evaluate the antioxidant activity of their hydroethanolic extracts obtained using a 2² full factorial design with three central points. The extracts were prepared at solid-to-solvent ratios of 1:5, 1:10 and 3:20 (w/v) and extracted in an ultrasonic bath for 5, 10 and 15 minutes. The physicochemical characteristics determined were moisture, ash and alcohol-insoluble solids contents using official gravimetric methods. The total phenolic compounds were determined using Folin-Ciocalteu method. Antioxidant activity was determined using DPPH-radical scavenging assay and ferric reducing antioxidant power (FRAP). Fresh geopropolis presented 4.75 ± 0.005% (m/m) moisture content, 82.8 ± 0.04% alcohol-insoluble solids, 42.16 ± 12.31% alcohol-soluble solids and 70.72 ± 0.76% ash content. Although the moisture, alcohol insoluble-solids and ash contents exceed the limits established by Brazilian quality standards for Apis mellifera propolis, these standards were not specifically developed for geopropolis, highlighting need for specific quality parameters for products obtained from Meliponini bees. The ultrasound extraction yield ranged from 4.13 to 7.19%. The total phenolic content achieved was 535.36 ± 3.01 to 732.42 ± 6.5 mg EAG/g; the antioxidant activities for DPPH and FRAP assays were 4,1 ± 0,03 – 5,85 ± 0,04 μg/mL and 1.1 ± 0.05 – 2.12 ± 0.14 mmol FeSO₄ equivalents/g, respectively. The design of experiments proposed did not show statistical significance in dependent responses, except for the total phenolic content which was influenced by the effect of both sample mass and time. Thus, the desirability function was calculated, and the result suggests a higher level of phenolics compounds and yield would be achieved under optimized conditions: 3:20 (w/v) proportion for 10 minutes in the ultrasonic bath (D = 0.80). The extracts obtained using the design of experiment exhibited relevant phenolic content and better antioxidant activity than previous studies. Nevertheless, these results emphasize the potential of M. interrupta geopropolis as a source of bioactive compounds and resources for the development of value-added products.

Keywords: Geopropolis; Stingless bees; Antioxidant; Physicochemical.

Acknowledgements: This study was financed by the Coordenação de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001 and FAPERJ (Processos E-26/ E-26/210.932/2024; E-26/204.549/2024). Support was also provided by UFAM, FAPEAM and INPA.