The effect of structural differences in anthocyanins from black goji berries on their stability and cellular antioxidant activity
Black fruited wolfberry is a perennial shrub plant that grows on the Qinghai Tibet Plateau. It has many ecological functions such as preventing soil salinization and improving the ecological environment. Pharmacological studies have also shown that black wolfberry has many activities such as anti-inflammatory, antioxidant, hypoglycemic and lipid-lowering, immune enhancement, anti fatigue, anti-inflammatory, etc. Its value is gradually being valued by society and has become a research hotspot.
Anthocyanins are prone to instability during application due to their own structure and other reasons, and stability restricts the development of anthocyanins. The hydroxyl or methyl group on the substituent of the B ring can reduce its stability, and acylation, as well as the type, quantity, and binding site of the sugar group, also affect the stability of anthocyanins. Chen’s research also indicates that external metal ions, oxidants, and reducing agents have a certain impact on the stability of anthocyanins in black goji berries. The structure of anthocyanins also has a significant impact on their biological activity. Rahman’s results indicate that 4 ‘- OH methylation significantly reduces the antioxidant activity of anthocyanins, while glycosides have a smaller effect on antioxidant activity compared to the structure of anthocyanin mother nuclei. It can be seen that stability and antioxidant activity are inseparable from structure. Therefore, discussing the influence of structure on both can help deepen our understanding of anthocyanins and promote their further development and utilization.

Black wolfberry is rich in anthocyanins, but current research is generally focused on independent studies of its anthocyanin stability and pharmacological activity. For example, in terms of stability, Hu evaluated the pH stability of anthocyanins in black goji berries, and the results showed that anthocyanins became more easily degraded with increasing pH. Luan also confirmed that polyphenol extracts have a certain stabilizing effect on anthocyanins in black goji berries. In terms of pharmacological activity, black wolfberry anthocyanins have good cell protective effects on PC12 cells and alleviate D-galactose-induced memory impairment. However, at present, there is no research discussing the structural changes of anthocyanins in black goji berries on their stability and cellular antioxidant activity, which to some extent restricts the research and application of black goji berries and anthocyanins. This study evaluated anthocyanin compounds through stability experiments, computational chemistry, and oxidative damage cell models. The discussion of their structural correlation can provide useful references for the stability and activity research of anthocyanins in black goji berries in the future.

Four monomeric compounds of anthocyanins from Lycium barbarum were obtained by semi preparative high-performance liquid chromatography, and their stability and structural correlation with cellular antioxidant activity were preliminarily evaluated. The results indicate that the trans structure has better stability than the cis structure under neutral and weakly alkaline conditions. The increase of sugar groups and the substitution of methoxy groups on the B ring of the mother nucleus can increase the stability of anthocyanins. The molecular simulation results indicate that the trans structure, increase in sugar groups, and substitution of methoxy groups on the B ring can all improve stability by shortening the molecular distance between the parent nucleus and the sugar chain. The results of cell viability experiments showed that anthocyanin compounds are non-toxic to cells and can improve oxidative damage induced by H2O2 in SH-SY5Y cells to a certain extent. Specifically, an increase in sugar groups can significantly reduce the level of LDH in damaged cells, and the trans structure has a more active advantage than the cis structure, with 1 being the most obvious. The research results indicate that structural trans acylation and an increase in the number of sugar groups can enhance the pH stability of anthocyanins in Lycium barbarum and improve the LDH level of oxidative damage induced by H2O2 in SH-SY5Y cells. This study conducted preliminary research on the stability and cellular antioxidant activity of four anthocyanin compounds isolated from black wolfberry, hoping to provide useful references for the development of the stability and activity of anthocyanins in black wolfberry in the future.