Palynological origin, Total Phenolic and Flavonoid contents and Antioxidant Properties of honey bee-collected pollen from Matelica (Marche, Italy): A seasonal analysis

Nowadays honey-bee collected pollen represents an apicultural product of great commercial interest due to its high nutritional value. Pollen is, in fact, generally referred to as a super-food; it contains high level of proteins (from 10% up to 40%), lipids (1-13%), carbohydrates (13-55%), minerals and vitamins (in particular of the B group) [1]. In addition, honey bee-pollen possesses antioxidant properties (mostly depending on the phenolic compounds) which are known to be very effective in fighting against free radicals; therefore, honey-bee collected pollen has high potential for both nutritional and medical applications [2]. However, the chemical composition of bee-pollen, may significantly changes according to the palynological and geographical origin, climatic conditions and month of collection [3-4]. Therefore, all these factors differently contribute to the final properties and biological activities of the bee-pollen (and thus, in turn, its therapeutic effects and nutritional properties). In this context, the present study aims to assess the palynological origin, total phenolic contents (TPC), total flavonoid content (TFC) and antioxidant properties of multifloral honey bee-collected pollen from a rural location in the area of municipality of Matelica (Marche Region, Italy). The project, realized in collaboration with the Cooperativa Apicoltori Montani of Matelica, has involved the analysis of multifloral pollen samples on a seasonal basis (from April to September 2016) by means of the following in vitro assays: a) the total phenolic contents (TPC) determined by the the Folin-Ciocalteu methods [5] using gallic acid as the standard compound; the total flavonoid contents determined by the aluminium chloride colorimetric assay developed by [6] using quercetin as reference standard and b) the 1, l-diphenyl-2-picrylhydrazyl (DPPH) Scavenging Assay [7] and Hydroxyl Radical Scavenging Assay (HRSA) [8] for the analysis of the antioxidant properties. All these assays were realized using lyophilized bee pollen ethanolic extracts (LBPE). Qualitative and quantitative palynological characterization of the 4 pollen samples, showed the presence of a total of more than 20 plant families, with Fabaceae, Rosaceae, Salicaceae, Brassicaceae and Asteraceae being the most abundant (from 20% up to 33%). Results indicated that there were significant differences (p ≤ 0.001) among pollen samples for total phenolic and flavonoid contents. TPC values ranged from 11.8 (September) to 23.8 (May) to mg GAE/gr,; TFC contents ranged from 5.98 (September) to 14.14 (May) mg QE/g. Furthermore, results of the DPPH and HRSA scavenging activities indicated that the lyophilized bee pollen ethanolic extracts have significant antioxidant properties. In particular, the highest TPC and TFC contents and antioxidant properties were recorded for the May pollen samples. The present study represent the first “seasonal fingerprint” of pollen properties in Italy. In final, our study aims to give a) a contribution to the economic valorization of this important local natural resource; and, b) to possibly define seasonal/monthly baseline values (i.e minimum and maximum values) for bee pollen properties in the area of Matelica. References [1] Almeida-Muradian L.B., Pamplona L.C., Coimbra S. and Barth O.M. Chemical composition and botanical evaluation of dried bee pollen pellets. J. Food Comp. Anal. 2005, 18, 105-111. [2] Denisow, B., Denisow-Pietrzyk, M. Biological and therapeutic properties of bee pollen: a review. J. Sci. Food Agr., 2016, 4303-4309 [3] Almaraz-Abaraca, N., Campos, M.G., Ávila-Reyes, J.A. Variability of antioxidant activity among honey-bee collected pollen of different botanical origin, J. Sci. Tech. Amer. 2004, 29, 574-578. [4] Szczesna, T., Rybak-Chielewska, H., Chmielewski, W. Sugar composition of pollen loads harvested at different periods of the beekeeping season, J. Apic. Sci. 2002, 46, 107-115. [5] Vattem AD, Shetty K (2002) Solid-state production of phenolic antioxidants from Cranberry pomace by Rhizopus oligosporus. Food Biotechnol, 2002, 16, 189–210 [6] Zhishen, J., T. Mengcheng, and Jianming W. The determination of flavonoid contents in mulberry and their scavenging effects on superoxide radicals. Food Chem. 1999, 64, 555-559 [7] Yildirim A, Mavi A, Kara AA Determination of antioxidant and antimicrobial activities of Rumex crispus L. extracts. J. Agri.c Food Chem. 2001, 49, 4083–4089 [8] Ravindran C, Varatharajan GR, Rajasabapathy R, Vijayakanth S, HarishKumar A, Ram M. A role for antioxidants in acclimation of marine derived pathogenic fungus (NIOCC 1) to salt stress. Microb. Pathog. 2012, 168–179