Two New Pyrrolidine Alkaloids, Radicamines A and B, as Inhibitors of .ALPHA.-Glucosidase from Lobelia chinensis LOUR.

Abstract

Several structurally related monocyclic and bicyclic polyhydroxy pyrrolidines have been reported to show various biological activities, such as competitive inhibition of glycosidases, [1][2][3][4] as antiviral agents, 5) and as acaricides. 6) In the course of our survey for biologically active constituents extracted from crude drugs with hot water, we have reported many pyrrolidine alkaloids, broussonetines from Broussonetia kazinoki SIEB. (Moraceae). [7][8][9][10][11][12][13][14] Our continuing search led us to isolate two new pyrrolidine alkaloid, radicamines A and B, from Lobelia chinensis LOUR. (Campanulaceae). This report deals with the structural elucidation and its inhibitory activities against a-glucosidase of these new natural products.The plant, Lobelia chinensis LOUR. (Japanese name "azemushiro"), is distributed throughout China, Taiwan, Korea, and Japan. The whole plants have been used as a diuretic, an antidote, hemostat, and as carcinostatic agents for stomach cancer in Chinese folk medicine. Various alkaloids, for example lobeline, lobelanine, lobelanidine and so on are known as constituents of this herb.The herb was extracted with hot water and the alkaloidal constituents were concentrated as described in the Experimental section. H-1 H COSY) cross-peaks and they were connected on the basis of the heteronuclear multiple bond correlation (HMBC) spectrum and characteristic mass fragment ion (m/z 131) to establish the planar structure (Fig. 2).The 1 H-and 13 C-NMR signals were reasonably assigned by heteronuclear single quantum coherence (HSQC), and distortionless enhancement by polarization transfer (DEPT), as shown in Table 1.The relative stereochemistry of the pyrrolidine moiety in 1 was determined by the vicinal coupling constants (J 2,3 ϭJ 3,4 ϭ 7.3 Hz, J 4,5 ϭ8.9 Hz) and nuclear Overhauser effects (NOEs) Two new pyrrolidine alkaloids, radicamines A and B were isolated as inhibitors of a a-glucosidase from Lobelia chinensis LOUR. (Campanulaceae). Radicamines A and B were formulated as (2S,3S,4S,5S)-2-hydroxymethyl-3,4-dihydroxy-5-(3-hydroxy-4-methoxyphenyl)-pyrrolidine (1) and (2S,3S,4S,5S)-2-hydroxymethyl-3,4-dihydroxy-5-(4-hydroxyphenyl)-pyrrolidine (2) on the basis of spectroscopic analyses and chemical methods.

Two New Pyrrolidine Alkaloids, Codonopsinol C and Codonopiloside A, Isolated from <i>Codonopsis pilosula</i>

“…8,9) In addition, pyrrolidine alkaloids, broussonetinines E and F isolated from the bark of Broussonetia kazinoki, were also α-glucosidase inhibitors. 10) Otherwise, some pyrrolidine alkaloids showed toxicity.…”

Differential Rapid Screening of Phytochemicals by Leaf Spray Mass Spectrometry

“…The compound belongs to a wellknown class of polyhydroxylated pyrrolidines. Although polyhydroxylated alkaloids with lipophilic moieties (hydroxyaryl or methoxyaryl substitutents) are known, 20,21 it is unusual for a lipophilic monoterpene to be bound via a linker.…”

New alkaloid from the aerial parts of Codonopsis clematidea

“…The n-hexane-, EtOAc-, and n-BuOH-soluble fractions were repeatedly subjected to silica gel, Sephadex LH-20, Toyopearl HW-40C, and Amberlite XAD-2 chromatography with various solvent systems and to preparative TLC and HPLC to yield compound 1 (12.5 mg) and 13 known compounds (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Compound 2 was identified as (+)-codonopsine (2) [6], which has been isolated previously from this plant source.…”