Thesis (M.Sc.)--Chulalongkorn University, 2011

Bee pollen is one of honeybee products. It is collected by foragers of Apis spp. and some species of stingless bees. It is the mixture of natural flower pollens, nectar, and secretion of bees. It is rich in nutrients such as sugars, proteins, lipids, vitamins, flavonoids, etc. It was reported that bee pollens provided various bioactivities such as antiproliferative, anti-allergenic, anti-angiogenic, and free radical scavenging activities, etc. In this research, it was aimed to investigate chemical constituents and to determine the free radical scavenging activity of bee pollen extracts. Bee pollens were directly collected from A. mellifera colonies in Chedeechai subdistrict, Pua district, Nan province, Thailand, in June, 2010. During that period, the majority of cultivated crops surrounding an apiary were corn. Crude bee pollen was extracted by EtOH and was partitioned by different solvents (hexane, CH2Cl2, and MeOH). Later, they were tested for free radical scavenging activity by DPPH assay. The absorbance was measured at 517 nm. The percentage of scavenging activity and effective concentration at 50% (EC50) were estimated. Crude CH2Cl2 extract originated from EtOH extract providing the most active free radical scavenging activity has the EC50 value of 7.47 ± 0.12 µg/ml. This crude was purified by quick column, size exclusion chromatography, and adsorption chromatography. The purity of all fractions in each step was observed by thin layer chromatography (TLC). Finally, chemical constituents in the most active fraction was analysed by nuclear magnetic resonance (NMR). Two compound structures were revealed. The first compound, a minor compound, was hydroquinone belonging in a phenolic compound group. The second compound, a major compound, was apigenin belonging to a flavone group. The properties of bee pollen were tested in term of total disaccharide sugar, reducing sugar, total phenolics, and total flavonoid contents. It could be concluded that not only bee pollens from Nan province in Thailand were nutritional, but it also had the free radical scavenging activity.