Syringic and cinnamic acids antiradical/antioxidant activities as R. ferruginea extract components and membrane physico-chemica

Syringic and cinnamic acids were previously identified as the major components on Rapanea ferruginea0s leaf extract. In this work, these phenolic acids were investigated and correlated in two aspects. The first one was referred to their role against DPPH and hydroxyl radicals, considering the concentration detected in R. ferruginea extract. The second one considered their effects on the physico-chemical properties of soy asolectin liposomes, such as hydration degree, trans-gauche isomerization, vibrational, rotational and translational motions, state-of-phase, size and surface charge. The half-maximum inhibitory concentration (IC50) related to syringic acid in DPPH assays was detected as 7.36  103 mM.
At the cinnamic acid highest tested concentration (8.23  103 mM), the activity against DPPH was
around 4.6%. Regarding hydroxyl radical-induced lipid peroxidation, the IC50 detected for syringic acid free in solution (free-form) was equivalent to 0.082  103 mM, a value 3.6 times lower than the detected for its liposome-loaded form. At the highest tested concentration (0.24  103 mM), the free-form cinnamic acid inhibited lipid peroxidation by 4 times the observed to its liposome-loaded form. Results showed that hydrogen donation is not the preferential mechanism in which the tested phenolic acids inhibit hydroxyl radical-induced lipid peroxidation. Syringic acid showed higher antioxidant potential than cinnamic acid, probably having a primordial role in the properties related to R. ferruginea. Liposomes’ physico-chemical data provided correlations between the phenolic acids’ antioxidant potential and their influence in the mobility of specific lipid groups. The findings of this work will contribute to the design and development of phenolic acids-based and plant extract-based pharmacological systems.

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