Bifunctional phenolic-choline conjugates as anti-oxidants and acetylcholinesterase inhibitors

Figures & data

Figure 1.  Inhibitors of AChE currently approved by FDA as drugs against AD.

Figure 2.  Caffeic acid, rosmarinic acid, and trolox, all nontoxic natural antioxidants.

Figure 3.  The synthesized choline ester derivatives of: 3,4-dimethoxycinnamic acid (1), cinnamic acid (2), caffeic acid (3), rosmarinic acid (4), and trolox (5).

Figure 4.  Synthesis of compound 1. Reagents and conditions: (i) SOCl₂, reflux; (ii) (MeO)₂SO₂, K₂CO₃, THF, reflux; (iii) NaOH, dioxane/H₂O, pH 12–14, r.t.; (iv) K₂CO₃, dioxane/H₂O, r.t.; and (v) DMSO, chlorocholine chloride (6), 60°C.

Table 1.  Results of AChE inhibition and antioxidant activity (DPPH assay) measured for the compounds in study, some parent compounds and standard AChE inhibitors.

Compound	AChE inhibition	Antioxidant activity
	IC50 (μM)^a	EC50 (μM)^b
Parent compounds (carboxylic acids)
3,4-Dimethoxycinnamic acid	7204^c	480
Cinnamic acid	9900 ± 700	675^d
Caffeic acid	5551^c	24.8 ± 0.2
Rosmarinic acid	1220 ± 80	6.4 ± 0.1
Trolox	3995 ± 6	13.2 ± 0.4
Choline esters
3,4-Dimethoxycinnamoylcholine chloride, 1	7.3 ± 0.8	303^d
Cinnamoylcholine chloride, 2	50 ± 7	371^d
Caffeoylcholine trifluoroacetate, 3	91 ± 6	30 ± 6
Rosmarinylcholine trifluoroacetate, 4	300 ± 30	4.3 ± 0.2
Troloxcholine trifluoroacetate, 5	1193 ± 93	38.4 ± 0.9
Standards
Tacrine	0.2^e	–
Donepezil	0.03^f	–
Galantamine	1.07^g	104^c
Rivastigmine	1.5^h; 48^g	–
BHT^i	–	15.7^j

^aAChEI (IC₅₀) in Tris buffer (50 mM, pH 8); ^bDPPH assay; ^cmaximal dose in the assay leading to a value inferior than 25% inhibition; ^dmaximal dose in the assay leading to a value inferior than 5% inhibition; ^eref. 52; ^fref. 20; ^gref. 35; ^href. 37; ⁱBHT = 3,5-di-tert-butyl-4-hydroxytoluene; ^jref. 53.

Figure 5.  Docking of compound 1 (blue) into the active site of TcAChE (PDB entry 1ACL). The catalytic triad is formed by Ser200, His440, and Glu327, the CAS is formed by Trp84, Phe330, and Glu199, and the PAS located at the entrance of the gorge is formed by Trp279, Tyr70, and Asp72.

Figure 6.  Effect of bifunctional phenolic-choline conjugates (1, 2, 3) on Abeta_1–42 and MPP⁺ toxicity in SH-SY5Y cells. SH-SY5Y cells were treated with Abeta_1–42 (1 μM) and MPP⁺ (1 mM) for 24 h, in the absence or the presence of 5 μM of compounds 1, 2, and 3. Results are expressed as the percentage of SH-SY5Y untreated cells, with the mean ± S.E.M. derived from six different experiments. P < 0.001, significantly different when compared with SH-SY5Y untreated cells; ^#P < 0.05; ^##P < 0.01, significantly different when compared with Abeta_1–42 treated cells; ^§P < 0.05; ^§§P < 0.01, significantly different when compared with MPP⁺ treated cells.