Assisted ultrasonic wave of vanillin derivatives synthesis and antioxidant activity using DPPH method

Abstract

In recent years, the need for compounds with antioxidant activities has expanded. Generally, the natures of these compounds involve the presence of conjugated double bonds, phenolic groups, and resonance effects on the structure. One of the compounds with the phenolic group is vanillin. It can be modified into the derivative of 1, 8-dioxo-octahydroxantene compound due to its aldehyde content. Meanwhile, 1, 8-dioxo-octahydroxantene compound has two 2- cyclohexenone rings bound in the pyran ring and one phenolic group, expected to carry more excellent antioxidant activities than vanillin. The 9-(4-hydroxy-3-methoxyphenyl)-3, 4, 5, 6, 7, 9- hexahydro -1H-xantene-1, 8(2H)-dione (Compound 1) was synthesized from 1, 3- cyclohexanedione and vanillin through Knoevenagel's condensation reaction aided with an acid catalyst with a single reaction phase. Besides, in this study, green chemistry was adopted using environmentally friendly catalysts from lime juice and ultrasonic wave. The synthesized compounds' structure was confirmed through the spectrophotometer IR, GC-MS, and 1H-NMR spectrometer, while its antioxidant activity was tested using the DPPH method. The reaction occurred with and without lime juice catalyst, producing yields of 70.58% and 6.65%, respectively. The results of the antioxidant activity test suggested that Compound 1 carried substantially robust antioxidant activities with IC50 of 0.99 ppm.