Antioxidative activity of sinapic acid and its derivatives in model lipid systems

Martinović, Neda (author), Abramovič, Helena (mentor), Poklar Ulrih, Nataša (comentor)

The effectiveness of sinapic acid and its derivatives varied with the test system, the type of free radicals and the mechanism of antioxidant activity. It was shown that early response parameters of free radical scavenging are adequate to evaluate differences between antioxidants with comparable endpoint (steady-state) activity. Among selected compounds syringic acid and sinapic acid showed the highest DPPH˙ and O2˙– scavenging activities (determined at steady-state) and the highest ability to inhibit lipid peroxidation in oil. Sinapic acid esters had the highest activities in oil-in-water emulsion and liposome suspension, and ethyl sinapate and propyl sinapate, furthermore, proved to be excellent ˙OH-scavengers. These esters, which were the most lipophilic, had the greatest effects on liposome bilayer thermal and enthalpic destabilisation of the gel state and increased the ordering of the liquid state of the lipids. This dual effect on the lipid bilayer might suggest that the esters initiate the formation of nanodomains with reduced fluidity that can capture hydroperoxides and thus inhibit lipid peroxidation. In the oleogel, the level of inhibition for the more polar compounds, sinapic acid, syringic acid and syringaldehyde, and less polar, 4-vinylsyringol and butyl sinapate, was at the same level, indicating the possible interactions of these less polar compounds with the oil structuring agent in oleogel. This research thus opened a new approach: the possibility of incorporating lipophilic antioxidants to prolong the oxidative stability of oleogel based products. It was shown that white mustard seeds provide excellent source of raw material for the recovery of value-added antioxidant compounds that are effective in preventing lipid peroxidation in systems such as oil and oleogel.

• Language: English
• Keywords: sinapic acid, sinapine, syringic acid, syringaldehyde, 4-vinylsyringol, ethyl sinapate, propyl sinapate, butyl sinapate, antioxidants, free radical scavenging, lipid peroxidation, emulsion, oil, oleoel, liposomes
• Work type: Doctoral dissertation
• Typology: 2.08 - Doctoral Dissertation
• Organization: BF - Biotechnical Faculty
• Publisher: [N. Martinović]
• Year: 2020
• PID: 20.500.12556/RUL-115068
• UDC: 577.1:547.587.53:66.964.3.097.8
• COBISS.SI-ID: 5181304
• Publication date in RUL: 11.04.2020

Secondary language

• Language: Slovenian
• Title: Antioksidativna učinkovitost sinapinske kisline in njenih derivatov v modelnih lipidnih sistemih

Abstract

Učinkovitost sinapinske kisline in njenih derivatov se razlikuje glede na testni sistem, vrsto prostih radikalov in mehanizem antioksidativnega delovanja. Pokazali smo, da so parametri zgodnjega odziva v lovljenju prostih radikalov ustrezni za ocenjevanje razlik med antioksidanti s primerljivo aktivnostjo v končni točki (v stanju ravnotežja). Med izbranimi spojinami sta siringinska kislina in sinapinska kislina pokazali največjo sposobnost lovljenja O2˙– in DPPH˙radikalov (določeno v stanju ravnotežja) in največjo sposobnost zaviranja peroksidacije lipidov v olju. Estri sinapinske kisline so imeli najvišjo aktivnost v emulziji olja-v-vodi in suspenziji liposomov; etil sinapat in propil sinapat pa sta se izkazali za odlična lovilca ˙OH radikalov. Estri, ki so najbolj lipofilni, imajo največji učinek na termično in entalpijsko destabilizacijo stanja gela liposomskega lipidnega dvosloja in povečajo urejenost v tekočem stanju lipidov. Ta dvojni učinek na lipidni dvosloj bi lahko pomenil, da estri sprožijo tvorbo nanodomen z zmanjšano fluidnostjo, ki ujamejo hidroperokside in s tem zavirajo peroksidacijo lipidov. V oleogelu je bila stopnja inhibicije za bolj polarne spojine, sinapinsko kislino, siringinsko kislino in siringaldehid, na isti ravni kot za, 4-vinilsiringol in butil sinapat, kar je pokazalo na možne interakcije teh manj polarnih spojin s sredstvom za strukturiranje olja v oleogel. Ta raziskava je tako odprla nov pristop: možnost vključitve lipofilnih antioksidantov za podaljšanje oksidativne stabilnosti izdelkov na osnovi oleogelov. Pokazali smo, da predstavljajo semena bele gorčice surovino z dodano vrednostjo za pridobivanje antioksidativnih spojin, ki so učinkovite pri preprečevanju peroksidacije lipidov v sistemih, kot sta olje in oleogel.

• Keywords: sinapinska kislina, sinapin, siringinska kislina, siringaldehid, 4-vinilsiringol, etil sinapat, propil sinapat, butil sinapat, antioksidanti, lovljenje prostih radikalov, lipidna peroksidacija, emulzija, olje, oleogel, liposomi