A New Tricyclic Alkaloid from Portulaca oleracea L.

Abstract

A new tricyclic alkaloid named portulacatone (1), i.e., 5,6‐dihydro‐8,9‐dihydroxy‐11H‐pyrrolo[2,1‐b] [3]benzazepin‐11‐one, together with eight known compounds, methyl 4‐hydroxyphenylacetate (2), p‐hydroxybenzaldehyde (3), vanillin (4), protocatechualdehyde (5), p‐hydroxybenzoic acid (6), iseluxine (7), oleracein E (8), and (+)‐(R)‐feruloyl malate (9) were isolated from aerial parts of Portulaca oleracea L. Their structures were elucidated based on spectroscopic analyses. Among them, compounds 1–7 and 9 were isolated from this medicinal plant for the first time. Compounds 1 and 7 showed dose‐dependent scavenging activities against DPPH (2,2‐diphenyl‐1‐picryl‐hydrazyl) free radical, with EC50 values of 14.36 μM and 9.98 μM, respectively, more potent than the natural antioxidant vitamin C (EC50 20.72 μM).

Catecholic Isoquinolines from Portulaca oleracea and Their Anti-inflammatory and β2-Adrenergic Receptor Agonist Activity

“…In addition to these four alkaloids, six other catechol-type isoquinolines were also identified: (S)-(−)-oleracein E (5), 6,7dihydroxy-1-methyl-3,4-dihydroisoquinoline (6), 20,21 6,7-dihydroxy-3,4-dihydroisoquinoline (7), 22 (S)-(−)-salsolinol (8), 23 (R)-(+)-1-isobutyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (9), 24 and (R)-(+)-1-benzyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (10). 25 Two catecholamines, dopamine (11) 26 and 2-sulfonic acid dopamine (12), 27 as well as methyl 5hydroxy-4-oxo-4H-pyran-2-carboxylate (i.e., comenic acid methyl ester) (13), 28 L-phenylalanine ( 14), L-tyrosine (15), and adenine (16), were identified through analysis of physiochemical and spectroscopic data (Supporting Information) or TLC comparisons to the standard compounds (5, 14, 15, and 16…”

“…Several decades later, new types of alkaloids are still routinely being discovered from P. oleracea. , In our continuous effort to discover novel bioactive constituents from P. oleracea , the two known catecholic isoquinolines oleracein E and iseluxine, 16 catecholic indoline glucosides, , and the catecholic benzazepine portulacatone were isolated . Because oleracein E exhibited antioxidant and neuroprotective activity in cellular and animal models, , we were curious if other bioactive catecholic isoquinolines were present in P. oleracea .…”

“…P. oleracea has anti-inflammatory and antiasthmatic functions. , Because the catecholic isoquinoline trimetoquinol [1-(3′,4′,5′-trimethoxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline] is an antiasthma drug that acts as a β 2 -AR agonist to exert a bronchodilator effect, higenamine [1-(4′-hydroxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline] and salsolinol ( 8 ) exhibit β 2 -AR agonist activity, and higenamine possesses anti-inflammatory activity, we hypothesized that catecholic isoquinolines of P. oleracea may also have anti-inflammatory and β 2 -AR agonist effects. Herein we screened catecholic alkaloids 1 – 12 as well as the known iseluxine ( 17 ) and portulacatone ( 18 ) for potential anti-inflammatory and β 2 -AR agonist activities. Compounds 1 – 12 , 17 , and 18 exhibited various dose-dependent anti-inflammatory effects in lipopolysaccharide (LPS)-induced RAW264.7 macrophage cells by reducing NO production.…”

“…Recently, a method of polyamide column chromatography using petroleum ether−EtOAc− MeOH as the mobile phase was developed by our group for the separation of catecholic isoquinolines from P. oleracea. Sixteen compounds were isolated and characterized using spectroscopic and chromatographic methods, including 10 catecholic isoquinolines [1-(5′-hydroxylmethylfuran-2-yl)-6,7dihydroxy-3,4-dihydroisoquinoline (1), 1-(furan-2-yl)-6,7-dihydroxy-3,4-dihydroisoquinoline (2), 2-(furan-2-ylmethyl)-6,7dihydroxy-3,4-dihydroisoquinolin-2-ium (3), ethyl (S)-(−)-(6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline)propanoate ( 4), (S)-(−)-oleracein E (5), 6,7-dihydroxy-1-methyl-3,4dihydroisoquinoline (6), 6,7-dihydroxy-3,4-dihydroisoquinoline (7), (S)-(−)-salsolinol (8), (R)-(+)-1-isobutyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (9), and (R)-(+)-1-benzyl-6,7dihydroxy-1,2,3,4-tetrahydroisoquinoline (10)] and two catecholamines [dopamine (11) and 2-sulfonic acid dopamine (12)]. The other four compounds were methyl 5-hydroxy-4oxo-4H-pyran-2-carboxylate (13), L-phenylalanine (14) tyrosine (15), and adenine (16) (Figure 1).…”

An Unusual Homoisoflavanone from Portulaca oleracea

“…It has been used in folk medicine as a diuretic, an antispasmodic, an antipyretic, an antiseptic, a vermifuge, an antiscorbutic, an analgesic, a muscle relaxant, and so on . A variety of biologically active compounds have been isolated from it . In our continuing search for bioactive compounds from P. oleracea , one new homoisoflavanones ( 5 ), along with six known compounds, portulacanones A‐D ( 1 – 4 , 6 ) and 2,2′‐dihydroxy‐4′,6′‐dimethoxychalcone ( 7 ) were isolated.…”