Antioxidant and UV-radiation absorption activity of aaptamine derivatives – potential application for natural organic sunscreens

Abstract

Antioxidant and UV absorption activities of three aaptamine derivatives were theoretically studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT).

New insights into the competition between antioxidant activities and pro-oxidant risks of rosmarinic acid

“…Moreover, Δ r G 0 values of these reactions are less negative than that of trolox and ascorbic acid being −8.7 and −9.4 kcal mol −1 for the reactions with HOO˙, and −7.6 and −8.3 kcal mol −1 for the ones with CH 3 OO˙, respectively. Besides, the lowest Δ r G 0 value of FHT between RA − and HOO˙ is very close to those obtained by the DFT/M05-2X method for piperidine[3,2- b ]demethyl(oxy)aaptamine (−5.0 kcal mol −1 ), 61 pandanusin (−5.0 kcal mol −1 ), citrusinine-I (−4.9 kcal mol −1 ), 62 and 5-hydroxynoracronycin (−4.6 kcal mol −1 ) 62 and remarkably lower than those of 9-amino-2-ethoxy-8-methoxy-3 H -benzo[de][1,6]naphthyridine-3-one (7.1 kcal mol −1 ) 61 and tryptamine (−3.8 kcal mol −1 ). 78 In contrast, the reactions occurring at the C–H positions are all unfavorable with positive Δ r G 0 values ranging from 1.2 to 25.6 kcal mol −1 for the HOO˙ radical and from 2.2 to 26.7 kcal mol −1 for the CH 3 OO˙ one.…”

“…The relatively low PA value at O2–H of the COOH group (23.3 kcal mol −1 ) probably indicates the presence of the mono-anionic form generated from the deprotonation at this position in water. This PA value is quite lower than that of piperidine[3,2- b ]demethyl(oxy)aaptamine (60.2 kcal mol −1 ), 61 pandanusin A (54.6 kcal mol −1 ), and 5-hydroxynoracronycin (36.5 kcal mol −1 ) 62 (obtained at the M05-2X/6-311++G(d,p) level of theory).…”

“…Indeed, the Δ r G 0 values of the RAF reaction at C20 are 2.4 and 9.8 kcal mol −1 for HOO˙ and CH 3 OO˙ radicals, respectively, whereas the ones at C21 are 9.7 and 10.4 kcal mol −1 , in turn. In addition, the lowest Δ r G 0 of RAF reactions between RA − and HOO˙ is lower than those obtained by the DFT/M05-2X method for 9-amino-2-ethoxy-8-methoxy-3 H -benzo[de][1,6]naphthyridine-3-one (5.2 kcal mol −1 ) 61 and tryptamine (2.5 kcal mol −1 ). 78 In contrast to FHT and PL, the Δ r G 0 value of the RAF reaction in the PEA solvent is slightly lower than that in water.…”

“…These values are higher than the BDEs of trolox and ascorbic acid calculated at the same level of theory, 79.3 and 78.6 kcal mol −1 , respectively. When compared with several other antioxidants in previous studies obtained by the same M05-2X method, the BDE value at the O3–H of RA is lower than that in water of 2-( sec -butyl)-7,8-dimethoxybenzo[de]imidazo[4,5,1- ij ][1,6]-naphthyridin-10(9 H )-one (84.9 kcal mol −1 ), 61 xanthyletin (87.1 kcal mol −1 ), 62 trans-p -coumaric acid (85.0 kcal mol −1 ) 6 and protocatechuic acid (83.9 kcal mol −1 ). 88 Furthermore, the hydrogen dissociation in the PEA solvent is slightly more favorable than that in water with a lower BDE value, for example, a BDE (O3–H) of 80.4 kcal mol −1 as compared to 83.3 kcal mol −1 in water.…”

“…Generally, the SOMO of HAT TSs is distributed along the H transition vector between the donor and the acceptor, whereas the one of PCET TSs is orthogonal to the transition vector. 61,93 As can be seen in Fig. 5 , the 2p orbitals of the acceptor (O atoms of hydroxyl group) and the ones of the donor (O atoms of the radicals) are interacted and distributed along the H-shifting vector.…”