Chemical characterization, antioxidant, cytotoxic and antibacterial activity of propolis extracts and isolated compounds from the Brazilian stingless bees Melipona quadrifasciata and Tetragonisca angustula

Abstract

Since chemical or pharmacological studies on the propolis of Brazilian native bees are scarce, the aim of this study was to evaluate the chemical profile, the antioxidant, cytotoxic and antibacterial activity of aqueous and hydro-alcoholic extracts and isolated compounds of propolis of the native bees, Melipona quadrifasciata and Tetragonisca angustula, against bacteria with (Gram-positive and Gram-negative) and without cell wall (mollicutes). The extracts presented a peculiar feature between green and yellow propolis. Despite the low content of flavonoid and phenolic compounds, a promising level of antioxidant activity without toxicity in the propolis extracts of M. quadrifasciata was observed. The best antimicrobial activity was that of the hydro-alcoholic extract against Mycoplasma pneumoniae and Ureaplasma urealyticum (MIC 125 μg/ml). We isolated two compounds and identified them from the aqueous and hydro-alcoholic extracts as the flavononol sakuranetin and gallic acid. Sakuranetin and gallic acid presented MICs of 50 and 25 μg/ml against Mycoplasma hominis and Mycoplasma genitalium respectively. Propolis from Brazilian native bees may constitute an alternative and undervalued source of compounds with biological activity. The mollicutes are the smallest self-replicating bacteria that constitute a model of cellular and molecular biology studies due to their small genome and restrict biochemical machinery. This is the first report investigating the potential of antibacterial molecules isolated from propolis of Brazilian native bees using this microorganism model. Our results contribute to a better understanding of the chemical and biological properties of these propolis types and provide evidence for its potential medicinal use.

Dado que los estudios químicos o farmacológicos sobre la propóleos de abejas nativas brasileñas son escasos, el objetivo de este estudio fue evaluar el perfil químico, la actividad antioxidante, citotóxica y antibacteriana de extractos acuosos e hidroalcohólicos y compuestos aislados de propóleos de abejas nativas, Melipona quadrifasciata y Tetragonisca angustula, contra bacterias con (Gram-positivas y Gram-negativas) y sin pared celular (mollicutes). Los extractos presentaron una característica peculiar entre el propóleos verde y el amarillo. A pesar del bajo contenido de flavonoides y compuestos fenólicos, se observó un prometedor nivel de actividad antioxidante sin toxicidad en los extractos de propóleos de M. quadrifasciata. La mejor actividad antimicrobiana fue la del extracto hidroalcohólico contra Mycoplasma pneumoniae y Ureaplasma urealyticum (Concentración mínima inhibitoria o CMI de 125 μg/ml). Se aislaron dos compuestos y se identificaron a partir de los extractos acuosos e hidroalcohólicos como flavononol sakuranetina y ácido gálico. Sakuranetina y ácido gálico presentaron CMI de 50 μg/ml y 25 μg/ml frente a Mycoplasma hominis y Mycoplasma genitalium, respectivamente. El propóleos de abejas nativas brasileñas puede constituir una fuente alternativa y subvalorada de compuestos con actividad biológica. Los mollicutes son las bacterias autorreplicantes más pequeñas que constituyen un modelo de estudios de biología molecular y celular debido a su pequeño genoma y restringida maquinaria bioquímica. Este es el primer informe que investiga el potencial de las moléculas antibacterianas aisladas de propóleos de abejas nativas brasileñas utilizando este modelo de microorganismos. Nuestros resultados contribuyen a una mejor comprensión de las propiedades químicas y biológicas de estos tipos de propóleos y proporcionan evidencia de su posible uso medicinal.

Keywords:

• propolis
• chemical profile
• antioxidant activity
• antibacterial activity
• mollicutes
• mycoplasma
• Brazilian native bees

Acknowledgment

We are grateful Professor Dr Geraldo Moretto for his kind help with the propolis samples and the fruitful discussions about bees, to Prof. Dr André Luís de Gasper for his help regarding the botanical origin of propolis, and to Celina N Yamanaka M.S. for her help with the antimicrobial tests on cell-walled bacteria. We also acknowledge Prof Dr Ieda Maria Begnini for her kind help with the analysis of the spectral data and Prof Dr Valdir Cechinel Filho for the NMR spectra, Dr Marina Beatriz Borgmann da Cunha for her aid in the preparation of the manuscript, and Davinder S Chandhock for the revision of the final version.