Chemical composition, botanical evaluation and screening of radical scavenging activity of collected pollen by the stingless bees Melipona rufiventris (Uruçu-amarela)

Tania M.S Silva,Antonio C.S Lins,Breno M Freitas,Igor T Reis,Maria De Fátima Agra,Eva M.S Silva,Celso A Camara

doi:10.1590/s0001-37652009000200003

Abstract

Stingless bees in Brazil are indigenous and found all over the country. Bee pollen is used for its nutritional value in the human diet. It is made up of natural flower pollen mixed with nectar and bee secretions. In order to evaluate the chemical composition, free radical scavenging activity, and botanical origin, sample of pollen loads from stingless bee, Melipona rufiventris (Uruçu amarela) was studied. The EtOAc extract of pollen of Melipona rufiventris yielded the following compounds: p-hydroxycinnamic acid, dihydroquercetin, isorhamnetin, isorhamnetin3-O-(6'-O-E-p-coumaroyl)-beta-D-glucopyranoside, luteolin, and quercetin. This is the first report of the isolation of isorhamnetin3-O-(6'O-E-p-coumaroyl)beta-D-glucopyranoside from pollen. The free radicalscavenging activities of different solvent extracts of pollen were determined using DPPH assay. This activity decreases in the order: EtOAc>EtOH>Hexane extract. It appears that the EtOAc extract of the pollen is a good scavenger of active oxygen species. The botanical evaluation of pollen loads showed the composition by two pollen types, with the dominant type (97.3%) being Scopariadulcis (L.) (Scrophulariaceae) and the minor one Senna obtusifolia (L.) Irwin & Barneby (Fabaceae). This suggests a specific foraging behavior in Melipona rufiventris bees, even in an environment with such a rich botanical diversity as the Northeastern Brazil.

Highlights

The Meliponin is a bee group of more than 300 species encountered around the world
The NMR spectra were used to identify the structures of the phenolics isolated from pollen loads of Melipona rufiventris as p-hydroxycinnamic acid (1), dihydroquercetin (2), isorhamnetin (3), isorhamnetin-3-O-(6"-OE- p-coumaroyl)-β-D-glucopyranoside (4), luteolin (5), and quercetin (6), Figure 1
In pollen loads of Melipona rufiventris the EtOAc mainly comprised of p-hydroxycinnamic acid, dihydroquercetin, isorhamnetin, isorhamnetin isorhamnetin-3-O-(6"O-E- p-coumaroyl)-β-D-glucopyranoside, luteolin, and quercetin

Summary

Introduction

The Meliponin is a bee group of more than 300 species encountered around the world. They are characterized as having social and bearing an atrophied and non-functional sting, which justifies their popular name of stingless bees (Roubik 1989). Brazil, they are indigenous and present all over the country, species differ from region to region (Nogueira-Neto 1997, Lima-Verde and Freitas 2002). They are indigenous and present all over the country, species differ from region to region (Nogueira-Neto 1997, Lima-Verde and Freitas 2002) Besides their importance as major pollinators of most wild plants and some cultivated species, honey and bee pollen of meliponins are source of food, and medicines (geopropolis) and income to rural populations. There is a strong culture of bee keeping and using their products in Brazil and other parts of the world where these bees are native (Freitas 1999)

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