Variação sazonal da própolis marrom-esverdeada de União dos Palmares durante 2020–2021: composição química e atividades antioxidante e antimicrobiana

Abstract

Propolis is a natural product that exhibits anti-inflammatory, antiviral, antimicrobial, antioxidant, immunostimulant, and anticancer activities. The aim of this dissertation was to evaluate the seasonal variation of chemical markers, total metabolites, and the in vitro antioxidant and antimicrobial activities of greenish-brown propolis extracts from the municipality of União dos Palmares (PMUP), Alagoas. A sample of PMUP in natura was obtained monthly from September 2020 to August 2021. The samples were extracted by maceration with 2 x 50 mL of 92.8% ethanol for 15 g of raw propolis. The following analyses were conducted on the 12 extracts: investigation of chemical markers by HPLC-DAD; quantification in assays of total phenolic content (TPC), total flavonoid content (TFC), and flavanones and dihydroflavonols content (FDC); estimation of antioxidant activity by the DPPH• assay; antimicrobial activity through broth microdilution test using MTT as an indicator; and calculation of the Pearson correlation coefficient to elucidate the correlation strength between TPC, TFC, and the results of antioxidant and microbiological assays. HPLC-DAD revealed that the markers of PMUP were similar to those of other green propolis, including Brazilian green propolis. Pinocembrin was the most concentrated bioactive compound, with an average of 74.49 ± 32.47 mg/g. Other biomarkers with high content included pinobanksin, artepillin-C, chrysin, pinostrobin, and galangin. The 12 extracts showed high levels of TPC, TFC, and FDC, demonstrating average concentrations of 81.1 ± 26.05 mg GAE/g, 38.45 ± 10.10 mg QE/g, and 1.59 ± 0.24 mg PE/20 mg, respectively. The average IC50 verified by the DPPH assay was 47.72 ± 13.02 µg/mL, indicating good antioxidant activity. The broth microdilution test with MTT, conducted for Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), and Candida albicans (ATCC 90028) showed that Gram-positive bacteria were more sensitive than Gram-negative. PMUP extracts had the lowest MICs in January 2021 and April 2021, months with the highest TFC and biomarkers throughout the study. Correlations were observed between TPC and TFC quantifications and MICs and IC50. Nearly all results allowed the definition of periods of better quality of PMUP: the first, from October 2020 to January 2021, the second, from April to July 2021. This is the first study on the seasonality of the new type of greenish-brown propolis.