The UV-Vis absorption and fluorescence spectra of proanthocyanidins at different pH values were studied, and the change of absorption peak position was analyzed. The intermediate stable states of proanthocyanidins in different pH conditions, the electron transition modes and emission spectra of these steady states were analyzed. Eight parts of proanthocyanidins, each with mass of 1.00 mg, were added to acetic acid buffer solution with different pH in turn. The absorption of samples at the same pH concentration was measured by UV-visible spectrophotometer and fluorescence spectrophotometer, spectrogram analysis was carried out. The absorption peak wavelength of proanthocyanidins did not change obviously in acid condition, the quantum yield of proanthocyanidins was low in different pH solutions, and the excited molecules returned to the ground state mainly by non-radiative transition. Under the same temperature conditions, the stability of proanthocyanidins decreased with the increase of pH, and the color of the solution ranged from orange to red. The charge distribution of hydroxyl groups analyzed the ability of combining free radicals at different sites of proanthocyanidins with hydroxyl groups, which suggested that proanthocyanidins may have better antioxidant activity.

Quinolones are widely used, but there are few reports on the application of fluorescent probe analysis. In this paper, we synthesized a tricyano-dihydrofuran (DCDHF-2-V) electron acceptor, and a (DCDHF-2-V)-quinolone fluorescent nanoprobe was designed. Its structure was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR) and ultraviolet (UV). A novel tricyano-dihydrofuran-ofloxacin fluorescent nanoprobe was established for the first time by fluorescence spectrophotometry. A novel fluorescent nanoprobe was obtained and used in the determination of ofloxacin in vitro. The results showed that tricyano-dihydrofuran can form stable charge transfer complex with ofloxacin, and it can be used for the determination of ofloxacin in drugs as a fluorescent probe. While important experimental steps are for the first time achieved in this study for future Quinolone fluorescent nanoprobe implementations, this method is simple and sensitive.

Due to the excellent antioxidant capacity of proanthocyanidins, combined with the antioxidant mechanism of anthocyanins, it inspired us to study the antioxidant capacity of proanthocyanidins and their complexes. In this article, we conducted antioxidant tests on proanthocyanidin-bovine serum albumin and procyanidin-metal complexes, using DPPH and ABTS methods to determine the antioxidant capacity of procyanidins and their complexes. The results show that compared with proanthocyanidins, the proanthocyanidin complex has a certain degree of improvement in the ability to scavenge free radicals. After being combined with metal ions, the ability to scavenge free radicals is significantly improved. When the ratio of proanthocyanidin B2 to Fe3+ is 2:1, the ability to scavenge free radicals is significantly enhanced.