Synthesis, in vitro antioxidant activity, and cytotoxicity of naringin acylhydrazone derivatives
Flavonoids are a class of natural benzo – γ – pyranone derivatives commonly found in the plant kingdom, with antibacterial, antioxidant, immune regulatory, chemopreventive, and anticancer properties, which are highly beneficial to human health. Naringin, as a dihydroflavonoid compound, also has biological activities such as antibacterial, anti-tumor, and antioxidant properties. Tutunchi and Filippin investigated the feasibility mechanism of naringin in combating COVID-19. Naringin can be used in combination with Vc and Ve to more effectively treat cadmium induced and arsenic induced oxidative stress-induced liver injury in Wistar rats. However, due to the poor lipid and water solubility of naringin itself, its bioavailability is not high. Therefore, the modification research of naringin has received widespread attention from all walks of life.

The phenolic hydroxyl groups at positions 7 and 4 ‘, as well as the carbonyl group at position 4, of naringin are relatively active. Therefore, the structure of naringin can be modified through chemical reactions to improve its water solubility and thus enhance its bioavailability. According to literature reports, hydrazide compounds have good antioxidant activity, antibacterial activity, anticancer activity, etc. However, due to the influence of amino groups in hydrazide, they have certain toxicity to organisms. Therefore, modifying hydrazide to obtain hydrazone is an effective means to improve the toxicity of hydrazide. Acyl hydrazone compounds also have good antibacterial, antioxidant, and anti proliferative properties. Therefore, based on the current research on structure-activity relationships and naringin modification, this article introduces a hydrazide group at position 4 to form an acylhydrazone, hoping to obtain naringin derivatives with both biological activity and reduced toxicity of the hydrazide structure. Conduct in vitro antioxidant activity and cytotoxicity experiments on the obtained derivatives on HEK293 cells to screen for high antioxidant activity and low toxicity substances, providing reference for further development and utilization.

In this experiment, 13 naringin acylhydrazone derivatives were synthesized using microwave-assisted methods, of which 12 have not been reported in the literature. The in vitro antioxidant activity of 13 derivatives was determined by ABTS, FRAP, and DPPH methods. The antioxidant activity of the obtained derivatives is stronger than that of naringin. Moreover, the antioxidant activity of the eight derivatives b, e, g, i, j, k, l, and m is particularly significant, and the antioxidant activity of the derivatives g, i, j, k, l, and m is comparable to BHT, indicating that the introduction of acylhydrazone groups at the 4-position carbonyl of naringin through reaction can effectively enhance the antioxidant activity of the parent compound. A structure-activity relationship analysis was conducted on the antioxidant activity of derivatives, which showed that when the R group was an electron withdrawing group, the charge density of the derivatives dispersed, and the stability of the free radical intermediates obtained from the reaction increased, resulting in stronger antioxidant activity than naringin itself. The results of the effect of 8 highly active derivatives on the survival rate of HEK293 cells showed that, except for e and m, the other derivatives were non-toxic to HEK293 in the concentration range of 0-25 μ mol/L. The non-toxic concentration range of derivative j to cells is 0-100 μ mol/L, while the detection results of derivatives g and k show that a large number of cells still survive within the concentration range of 0-50 μ mol/L. However, the cytotoxicity of the obtained derivatives is stronger than that of naringin, indicating that while introducing acylhydrazone groups to increase antioxidant activity, the cytotoxicity of the compound is also increased at different levels. This provides a reference basis for the dosage of additives in subsequent studies of various derivatives. Therefore, after initial screening, derivatives g, j, and k have good antioxidant activity and low cytotoxicity. Among them, derivative j has both strong antioxidant activity and low cytotoxicity, and has certain application prospects. This provides a basis for further development and research. The structure-activity relationship analysis of the antioxidant activity of 13 derivatives provides direction for future synthetic design.