Determination of total phenolics, flavonoids, and B-group vitamins in dried and fresh-frozen bee pollen

Introduction. Bee pollen (BP) is a natural apitherapeutic product collected by honeybees from various plants. It is widely recognized for its rich composition of bioactive compounds, including phenolics, flavonoids and B group vitamins. In Lithuania, BP is most commonly prepared by drying while freezing of pollen right after collection is more prevalent in other countries. It is relevant to compare the total phenolic, flavonoid content as well as B-group vitamins in bee pollen prepared using different methods. Materials and methods. BP was obtained from an apiary in Talkoniai, Pasvalys, Lithuania. A portion was dried at +28°C (day 1) and at +35°C (day 2), the remaining portion was frozen at -20°C and at - 80°C. Ethanolic (70 %) extracts were prepared. The compounds were quantified spectrophotometrically: total phenolic content (TPC) by the Folin–Ciocalteu method [1] and total flavonoid content (TFC) by the AlCl₃ [2]. The content of B vitamins was evaluated using UPLC–MS/MS method in aqueous extracts. Results and discussion. The total phenolic content (TPC) in dried bee pollen (BP) samples was 12.4± 0.5 mg GAE/g DW, while in fresh-frozen samples it was 10.9±0.1 mg GAE/g DW at both –20 °C and –80 °C; the difference between them was not statistically significant. The total flavonoid content (TFC) was 7.2±0.5 mg RE/g DW in dried BP, 7.4±1.6 mg RE/g DW at – 20°C, and 6.2±1.0 mg RE/g DW at–80°C (p<0.05). Among B-group vitamins, the highest concentration was observed for pantothenic acid (B5), ranging from 2.6 to 3.2 µg/g DW, followed by thiamine (B1) (2.4–2.5 µg/g DW) and nicotinamide (B3) (0.8–2.3 µg/g DW) in both frozen and dried BP samples. The lowest content was determined for riboflavin (B2) (0.3–0.7 µg/g DW). The bee pollen samples analyzed were of mixed botanical origin, predominantly from Taraxacum officinale (L.) Weber ex F.H.Wigg., Salix alba (L.), Malus domestica Borkh, Syringa vulgaris (L.), Acer platanoides (L.), Aesculus hippocastanum (L.), Trifolium hybridum (L.), and Brassica napus (L). Conclusions. Based on the obtained results, the total phenolic and the total flavonoid content of bee pollen remained relatively stable across drying and freezing conditions, indicating that phenolic compounds are resistant to temperature variations. Among B-group vitamins, pantothenic acid (B5) was the most abundant, followed by thiamine (B1) and nicotinamide (B3), while riboflavin (B2) showed the lowest levels.