Tricolorin A, Major Phytogrowth Inhibitor from Ipomoea tricolor

Abstract

The allelopathic potential of Ipomoea tricolor (Convolvulaceae), used in Mexican traditional agriculture as a weed controller, has been demonstrated by measuring the inhibitory activity of organic extracts on seedling growth of Amaranthus leucocarpus and Echinochloa crus-galli. Bioactivity-directed fractionation of the active CHCl3 extract led to the isolation of the allelopathic principle, which turned out to be a mixture of the so-called "resin glycosides" of convolvulaceous plants. The structure of tricolorin A, the major phytogrowth inhibitor present in the active fraction, was elucidated as (11S)-hydroxyhexadecanoic acid 11-O-alpha-L-rhamnopyranosyl-(1-->3)-O-alpha-L-[2-O-(2S-methylbutyryl)-4 -O- (2S-methylbutyryl)] rhamnopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->2)-beta-D-fucopyran oside- (1,3"-lactone)[1], based on chemical methods and spectral analysis including 1H-1H COSY, 1H-13CHETCOR, long range 1H-13C COLOC, and selective INEPT experiments. Bioassays showed that radicle elongation of the two weed seedlings tested was inhibited by tricolorin A [1] with IC50 values ranging from 12 to 37 microM. Staphylococcus aureus was sensitive to compound 1 with an MIC value of 1.8 micrograms/ml. Significant cytotoxic activity against cultured P-388 and human breast cancer cells (ED50 2.2 micrograms/ml) was demonstrated for compound 1, and it also inhibited phorbol 12,13-dibutyrate binding using calf brain homogenate as a source of protein kinase C (IC50 43 microM).

Crystal Structure of Tricolorin A: Molecular Rationale for the Biological Properties of Resin Glycosides Found in Some Mexican Herbal Remedies

“…We now know that the phytotoxins involved are the resin glycosides, collectively called tricolorins. [2,3] Until recently, the structural complexity of these mixtures seriously hampered the isolation of their individual constituents. The application of recycling highperformance liquid chromatography has allowed no less than 10 lipooligosacharides to be isolated from the aerial parts of "heavenly blue".…”

“…The application of recycling highperformance liquid chromatography has allowed no less than 10 lipooligosacharides to be isolated from the aerial parts of "heavenly blue". [2][3][4] Tricolorin A was the first member of the series to be fully characterized through a combination of NMR and MS methods. [2,3] This compound consists of the tetrasaccharide l-rhamnopyranosyl-(1!3)-O-a-l-rhamnopyrasonyl-(1!2)-O-b-d-glucopyranosyl-(1!2)-O-b-d-fucopyranoside linked to jalapinolic acid to form a macrocyclic ester with a 19-membered ring (Scheme 1).…”

“…[2][3][4] Tricolorin A was the first member of the series to be fully characterized through a combination of NMR and MS methods. [2,3] This compound consists of the tetrasaccharide l-rhamnopyranosyl-(1!3)-O-a-l-rhamnopyrasonyl-(1!2)-O-b-d-glucopyranosyl-(1!2)-O-b-d-fucopyranoside linked to jalapinolic acid to form a macrocyclic ester with a 19-membered ring (Scheme 1). Following the elucida-tion of its chemical structure, total syntheses of tricolorin A in its natural enantiomeric form were developed by Larson and Heathcock, and by Lu and collaborators.…”

“…[5,6] Fürstner and Müller later used a ring-closing-metathesis strategy to form the macrolactone moiety and succeeded in synthesizing tricolorin A [7] and several other resin glycosides. [8,9] Tricolorin A demonstrates several biological activities of therapeutic interest, such as mammalian cytotoxicity against cultured P-338 and human breast cancer cells, [2] antibacterial activity against Staphyloccocus aureus and Mycobacterium tuberculosis, [1] and antifungal potential correlated to its (1!3)b-d-glucan synthase inhibitory activity. [10] In the cover crop, tricolorin A acts as a nonprotonophoric uncoupler of photophosphorylation and inhibits electron transport in the photosystem II of chloroplasts.…”

Does Soil under Natural <i>Tithonia diversifolia </i>Vegetation Inhibit Seed Germination of Weed Species?

“…), alegría and amaranth (Amaranthus hypochondriacus L.). Similarly, the allelopathic potential of Ipomoea was described by [17,18] identified Tricolorin A as the major phyto-growth inhibitor from the resin glycoside mixture of the plants.…”