Brazilian red propolis extracts: study of chemical composition by ESI-MS/MS (ESI+) and cytotoxic profiles against colon cancer cell lines

Red propolis is a natural resin mixture produced by honeybees and presents a source of active compounds with a variety of biological activities. In this study, we describe the chemical characterization and potential antitumor activity of total extract of Brazilian red propolis and its fractions. Fractions were obtained through column chromatography revealing 14 different compounds in all samples, which were determined and distinguished of other isobar molecules by fragmentation pathways by ESI-MS/MS in positive mode. Some molecules as cis-asarone or trans-isoelemicin were identified and distinguish from elemicin compound and vestitol or isovestitol were also distinguished from neovestitol by fragmention pathway. Other important compounds as liquiritigenin was differentiated from isoliquiritigenin and formononetin from dalbergin.

MTT viability assay showed different toxicity in cell lines after exposition to total extract and fractions. Fractions 05 and 06 had more selectivity against HT-29 and HCT-116 cancer cells, respectively, in relation to normal cells. IC₅₀ (ranging of 72.45 ± 6.57 to 73.58 ± 1.00 μg/mL) in cancer cells were lower than reported in total extracts of propolis. May-Grunwald/Giemsa staining revealed cellular morphological changes after exposition to higher concentrations of red propolis extracts. Fractionation techniques can contribute to reduce chemical diversity verified in propolis mixtures, generating fractions with improved biological activity and contributing to the development of new strategies for discovery of natural compounds against cancer.