| Bee pollens are fine powders collected from flowering plants by worker bees with added nectar andbee secretions. China is the largest producer of bee pollens in the world and the trading volume reached3500tons in2012. Bee pollens have different health benefits, such as aiding recovery from chronicillness, slowing the aging process down and helping lower cholesterol levels. Various biologicalactivities of bee pollens can be attributed to the nutrients and phytochemicals, such as proteins, aminoacids, vitamins, polyphenolics, carotenoids and fatty acids.Fatty acids are one of the most important nutrients contained in bee pollens and vary greatlydepending on the species of bee pollen. As reported by different authors, the fatty acid composition andcontents show great variability for the same kind of pollen.In this study,20species of bee pollen from China were collected to analyze fatty acid composition.Crude fats from bee pollen samples were extracted by Soxhlet extraction. Their fatty acid compositionswere studied by gas chromatography-mass spectrometry (GC-MS) with selected-ion monitor (SIM), andquantified by external standard method with mixed standards. Choice of catalysts can have a significanteffect on results of qualitative analysis as well as quantitative analysis. One of aims of this work was tostudy the changes offatty acid levels using different catalysts in an attempt to establish anoptimummethod of methyl ester for bee pollens.The crude fat was methyl-esterified by alkali catalyst, acidcatalyst and BF3catalyst respectively. The results showed that fatty acids among the five kinds of pollenwere obviously different. BF3catalyst for methyl esterification was superior to acid catalyst and alkalicatalyst.Fatty acids were identified via gas chromatography-mass spectrometry (GC-MS) with selected-ionmonitor (SIM), and the content of target fatty acids were quantified with external standard method.Ourresults show that in virtually all bee pollen samples were characterized by a wide variety of FAs, but notin high levels. The total fatty acids average content of all bee pollen samples was5.03mg/g, rangingfrom2.70mg/g in Peach blossom pollen to10.63mg/g in dandelion pollen. The highest of UFAs(unsaturatedfattyacids) was observed on dandelion pollen with the value of6.77mg/g. The highest ofMUFAs (monounsaturatedfattyacids) was observed on rape pollen with the value of1.96mg/g, and thehighest of PUFAs (polyunsaturatedfattyacids) was on yellow rose pollen with5.91mg/g.These20samples contained a large number of FAs, and some important UFAs were also identified. Thelinoleicacid, linolenicacid, arachidonicacid and nervonic acid have a great importance because of theirphysiological functions. Compared with the contents of SFA, most samples had higher contents ofUFA.All of bee pollen samples showed high levels of linoleicacid and linolenicacid with the average of0.53mg/g and1.56mg/g. ARA detected in16bee pollens reached an level of0.17mg/g. Nervonic acidwas found in16bee pollen samples in the average concentration of0.33mg/g. Without an adequatesupply of these UFAs, insects are not capable of completing their development and life cycle. Our results suggest that bee pollens are rich in FAs, and the composition vary greatly depending onthe species. On the other hand, some physiological functions of bee pollens may be attributed to its FAcomposition. Thus, we hypothesize that linolenic acid, linoleic acid, ARA and nervonic acid canprovide essential nutrients in bee breads to play a vital role in honeybees’ growth and development. |
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