Flavonoids in the buds of eight Populus species and hybrids were detected and compared with the aid of an optimized TLC method. Separation of 17 flavonoid aglycones belonging to different groups, namely, flavones, flavonols, flavanones and flavanonols, previously described as constituents of poplar buds, was performed on silica gel plates using a hexane/ethyl acetate/formic acid (60:40:1.3, V/V/V) mixture as the mobile phase. Pinocembrin and pinostrobin were found in the majority of analyzed poplar buds. For quantitative analysis of both compounds, two TLC evaluation modes, densitometric and videodensitometric, were compared and the established methods were validated. Concentrations of flavanones in some extracts differed slightly or significantly due to the analyzed plant matrix complexity and the TLC evaluation mode applied. Poplar buds rich in flavanones originated from P. × canadensis ‘Robusta’ (1.82 and 2.23 g per 100 g, resp.) and P. balsamifera (1.17 and 2.24 g per 100 g, resp.).
3. S. Dudonné, P. Poupard, P. Coutière, M. Woillez, T. Richard, J. M. Mérillon and X. Vitrac, Phenolic composition and antioxidant properties of poplar bud (Populus nigra) extract: individual antioxidant contribution of phenolics and transcriptional effect on skin aging, J. Agric. Food Chem.59 (2011) 4527–4536; https://doi.org/10.1021/jf104791t
4. K. Wang, J. Zhang, S. Ping, Q. Ma, X. Chen, H. Xuan, J. Shi, C. Zhang and F. Hu, Anti-inflammatory effects of ethanol extracts of Chinese propolis and buds from poplar (Populus × canadensis), J. Ethnopharmacol.155 (2014) 300–311; https://doi.org/10.1016/j.jep.2014.05.037
5. N. Debbache-Benaida, D. Atmani-Kilani, V. B. Schini-Keirth, N. Djebbli and D. Atmani, Pharmacological potential of Populus nigra extract as antioxidant, anti-inflammatory, cardiovascular and hepatoprotective agent, Asian Pac. J. Trop. Biomed.3 (2013) 697–704; https://doi.org/10.1016/S2221-1691(13)60141-0
6. E. Wollenweber, Flavonoidmuster als systematisches Merkmalin der Gattung Populus Biochem. Syst. Ecol.3 (1975) 35–45.
8. Y. K. Park, S. M. Alencar and C. L. Aguiar, Botanical origin and chemical composition of Brazilian propolis, J. Agric. Food Chem.50 (2002) 2502–2506; https://doi.org/0.1021/jf011432b
9. J. Adelmann, M. Passos, D. H. Breyer, M. H. Rocha dos Santos, C. Lenz, N. F. Leite, F. M. Lanςas and J. D. Fontana, Exotic flora dependence of an unusual Brazilian propolis: the pinocembrin biomarker by capillary techniques, J. Pharm. Biomed. Anal.43 (2007) 174–178; https://doi.org/10.1016/j.jpba.2006.07.014
10. V. Bankova, A. Dyulgerov, S. Popov, L. Evstatieva, L. Kuleva, O. Pureb and Z. Zamjansan, Propolis produced in Bulgaria and Mongolia: phenolic compounds and plant origin, Apidologie23 (1992) 79–85.
11. W. Greenaway, J. May, T. Scaysbrook and F. R. Whatley, Compositions of bud and leaf exudates of some Populus species compared, Z. Naturforsch. C: Biosci.47 (1992) 329–334; https://doi.org/10.1515/znc-1992-0602
12. J. Zhang, X. Cao, S. Ping, K. Wang, J. Shi, C. Zhang, H. Zheng and F. Hu, Comparisons of ethanol extracts of Chinese propolis (poplar type) and poplar gums based on the antioxidant activities and molecular mechanism, Evid-Based Complem. Altern. Med.2015, Article ID 307594 (15 pages); https://doi.org/10.1155/2015/307594
13. Z. Cui-ping, H. Shuai, W. Wen-ting, P. Shun, S. Xiao-ge, L. Ya-jing and H. Fu-Iiang, Development of high-performance liquid chromatographic for quality and authenticity control of Chinese propolis, J. Food Sci.79 (2014) C1315-C1322; https://doi.org/10.1111/1750-3841.12510
14. A. Rasul, F. M. Millimouno, W. A. Eltayb, M. Ali, J. Li and X. Li, Pinocembrin: A novel natural compound with versatile pharmacological and biological activities, BioMed. Res. Int.2013, Article ID 379850 (9 pages); https://doi.org/10.1155/2013/379850
17. J. Bertrams, M. B. Müller, N. Kunz, D. R. Kammerer and F. C. Stintzing, Phenolic compounds for botanical origin determination of German propolis samples based on TLC and TLC-MS, J. Appl. Bot. Food Qual.86 (2013) 143–153; https://doi.org/10.5073/JABFQ.2013.086.020
18. J. A. Duke, CRC Handbook of Phytochemical Constituents of GRAS Herbs and Other Economic Plants, CRC Press, Boca Raton (FL) 1992.