Monoamine oxidase inhibition by monoterpene indole alkaloids and fractions obtained from Psychotria suterella and Psychotria laciniata

Figures & data

Table 1.  Description of the main peaks observed in the HPLC–PDA and UHPLC/HR–TOF–MS analyses performed for SAE and LAE.

Fraction	Peak no.	HPLC-PDA		UHPLC/HR–TOF–MS			Alkaloid	RP-MPLC fraction
		Retention time (min)	UV spectrum λmax (nm)	Retention time (min)	Pseudo-molecular ion [M + H]^+	Molecular formula (calc.)
SAE	1	22.193	247, 303, 370	1.08	527.1982	C27H31N2O9	1^a	SA E-F1
	2	23.393	238, 307, 337	1.16	733.2667	C38H41N2O13	1 derivative^b	SAE-F1
	3	31.986	225, 280	1.49	499.2083	C26H31N2O8	2^a	SAE-F2
	4	50.714	223, 291	2.31	351.1696	C21H23N2O3	3^c	SAE-F3
	5	51.575	220, 289	2.31	351.1696	C21H23N2O3	4^c	SAE-F3
LAE	1	22.035	247, 303, 370	1.08	527.2010	C27H31N2O9	1^a	LAE-F1
	2	23.258	238, 307, 337	1.15	733.2577	C38H41N2O13	1 derivative^b	LAE-F1 / LAE-F2
	3	31.949	225, 280	1.48	499.2092	C26H31N2O8	2^a	LAE-F3
	4	50.657	223, 291	2.31	351.1697	C21H23N2O3	3^c	LAE-F4
	5	51.505	220, 289	2.31	351.1697	C21H23N2O3	4^c	LAE-F4
1		22.059	249, 303, 371	1.08	527.2004	C27H31N2O9
2		31.890	225, 280	1.48	499.2091	C21H23N2O3

^aStructures of isolated alkaloids confirmed by 1H NMR analyses (Table S2).

^bPseudo-molecular ion in positive mode according to (E)-O-(6′)-cinnamoyl-40-hydroxy-30,50-dimethoxy-lyaloside²⁵.

^cStructures confirmed by 1H NMR analyses from the mixtures of 3 and 4 obtained by CPTLC (Table S2).

Figure 1.  Chromatograms and UV spectra obtained by LC-PDA for the alkaloids fractions of P. suterella (SAE) and P. laciniata (LAE). Peak 1: UV spectrum characteristic for βC nucleus (further characterized as 1 by co-injection with the isolated standard and by UHPLC/HRTOF-MS and NMR analyses). Peak 2: UV spectrum characteristic of βC nucleus (further characterized as a possible 1 derivative by UHPLC/HR-TOF-MS analyses²⁵). Peak 3: UV spectrum characteristic of THβC MIAs (further characterized as 2 by co-injection with the isolated standard and by UHPLC/HR-TOF-MS and NMR analyses). Peaks 4 and 5: UV spectra characteristic of compounds possessing vallesiachotamine-like nucleus (further characterized as 3 and 4 by GC-MS, UHPLC/HR-TOF-MS and NMR analyses).

Figure 2.  Structures of the alkaloids lyaloside (1), strictosamide (2), vallesiachotamine (3), and isovallesiachotamine (4).

Table 2.  MAO-A inhibitory activity of fractions and monoterpene indole alkaloids from P. suterella and P. laciniata.

Sample	MAO-A
	µg/mL^c	IC50 (µg/mL)	Hill coefficient	Maximun inhibition (%)	R^2
SAE^a	0.1–50	1.37 ± 1.05	1.021	97.78	0.9968
LAE^b		2.02 ± 1.08	1.606	97.25	0.9838
SAE-F1	0.1–500	6.66 ± 1.08	0.9887	98.64	0.9946
SAE-F2		21.98 ± 1.18	1.065	97.11	0.9954
SAE-F3		0.57 ± 1.12	1.035	98.99	0.9981
LAE-F1	0.1–500	14.66 ± 1.10	1.126	99.08	0.9909
LAE-F2		2.15 ± 1.15	0.9691	98.07	0.9885
LAE-F3		8.32 ± 1.12	0.8278	99.09	0.9916
LAE-F4		1.05 ± 1.15	0.8240	98.65	0.9956
Lyaloside	0.1–500	50.04 ± 1.09	1.164	86.65	0.9919
Strictosamide		132.5 ± 1.33	0.9247	82.22	0.9879

^aSAE: alkaloid fraction of P. suterella.

^bLAE: alkaloid fraction of P. laciniata.

^cConcentrations tested for IC₅₀ determinations (μg/mL).

Table 3.  MAO-B inhibitory activity of fractions and monoterpene indole alkaloids from P. suterella and P. laciniata.

Sample	MAO-B
	µg/mL^c	IC50 (µg/mL)	Hill coefficient	Maximun inhibition (%)	R^2
SAE^a	1.0–250	55.44 ± 1.09	1.817	71.38	0.9791
LAE^b		61.15 ± 1.06	2.884	72.03	0.9774
SAE-F1	0.1–500	69.15 ± 1.08	1.275	93.24	0.9937
SAE-F2		234.0 ± 1.73	1.072	77.85	0.9710
SAE-F3		68.14 ± 1.10	1.265	96.36	0.9936
LAE-F1	0.1–500	116.1 ± 1.28	1.035	85.28	0.9842
LAE-F2		57.74 ± 1.08	1.328	95.39	0.9909
LAE-F3		133.1 ± 1.15	1.968	88.35	0.9798
LAE-F4		50.77 ± 1.20	1.143	90.42	0.9747
Lyaloside	0.1–500	306.6 ± 1.40	2.245	61.29	0.9418
Strictosamide		162.8 ± 1.26	1.805	57.69	0.9554

^aSAE: Alkaloid fraction of P. suterella.

^bLAE: Alkaloid fraction of P. laciniata.

^cConcentrations tested for IC₅₀ determinations (μg/mL).

Valverde J, Tamayo G, Hesse M. β-Carboline monoterpenoid glucosides from Palicourea adusta. Phytochemistry 1999;52:6.

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