Pterostilbene fluorescent probes as potential tools for targeting neurodegeneration in biological applications

Figures & data

Figure 1. Chemical structures of resveratrol (Res) and pterostilbene (Ptb) and their positive effects in the brain. On the right side the structure of Ptb factionalised on phenolic ring with benzofurazan 1 (yellow) and with rhodamine B-isothiocyanate 2 (pink), respectively.

Scheme 1. (i) K₂CO₃, anhydrous DMF, 50 °C, 8 h, then r.t., 36 h. (ii) CF₃COOH, DCM, r.t., 12 h, Et₂O • HCl, 0 °C. (iii) LiOH, NDB H₂O/THF, r.t., 12 h. (iv) NaOH 0.1 M. (v) DMF, Rhodamine-B Itc, r.t, 48 h.

Table 1. Maximum absorption wavelengths and ε values of NBD, Res, 1 and 2.

Sample	λmax (nm)	ε (cm^−1 M^−1)
NBD	469	7358
Res	310^a	44,307
1	325	48,574
2	280	31,401

^aAs expected from literature⁴⁵ Res absorption spectrum shows two main peaks at 310 nm and at 319 nm, respectively.

Table 2. Excitation wavelength, emission wavelength and emission intensity (a.u.) values of NBD, Res, 1 and 2.

Sample	λexc (nm)	λemis (nm)	Iemis (a.u.)
NBD	469	545	271
Res	325	397^a	53
1	458	537	19
2	319	575	271

^aEmission spectrum of Res shows one main peak at 397 nm, as expected from the literature⁴⁵.

Figure 2. Absorption and emission spectra collected on 1 and 2.

Figure 3. Carbon K-edge spectrum (a), nitrogen K-edge spectrum (b), and oxygens K-edge spectrum (c) of samples 1 and 2.

Figure 4. FTIR spectra of samples 2 (a), 1 (b) and of 7-nitrobenzofurazan (c).

Figure 5. Analyses of cellular DNA content obtained from propidium iodide assay (PI) in SH-SY5Y neuroblastoma (left) and MCF-7 breast cancer (right) cells. (a) Cells were treated for 48 h with either vehicle (ethanol/DMEM, 1/10) or resveratrol (Res, 1 µM) or with different Pterostilbene (Ptb) or its fluorescent derivatives (1 and 2) concentrations. Data are means ± SD of height (SH-SY5Y) or five (MCF-7) different experiments. (b) Typical Western blot of five different experiments of PARP-1 (uncleaved 116 kDa, cleaved 89 kDa) in cells treated as in (a).

Figure 6. Effect of pterostilbene (Ptb) and its fluorescent derivatives (1 and 2) on neuroglobin (NGB) levels in neuronal-derived cells. Western blot (upper panel) and densitometric analyses (bottom panel) of NGB levels in SH-SY5Y cells. Cells were treated for 24 h with resveratrol (R, 1 µM) or with different compound concentrations. The amount of NGB was normalised by comparison with α-tubulin levels. Data are the mean ± SD of five different experiments. p < 0.001 was determined with ANOVA followed by Bonferroni test with respect to the vehicle (*) or to R-treated samples (°).

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