Structure reinvestigation of conyzorigun, a new chromone from Ageratum conyzoides

Abstract

A highly oxygenated chromone, conyzorigun (1 ), from Ageratum conyzoides plants was earlier reported to contain a novel stable ketene acetal system by virtue of an oxygen linkage between the benzopyrone and phenyl moieties. A reinvestigation of this structure in the light of biosynthetic experiments followed by chemical degradation is now described. The results obtained indicate that conytorigun does not contain the above-described oxygen linkage, being a flavone of a known structure, viz. eupalestin (4).Adesogan and Okunade ' have reported the isolation of a new chromone, conyzorigun (l), C, H,,O , , from Ageratum conyoides plants as a minor constituent. This structure was assigned by them on the basis of u.v., i.r., ' H and ' 3C n.m.r. data together with evidence from alkali degradation of the compound which yielded the products (2) and (3). In view of the presence of such an unusual oxygen linkage between the benzopyrone and phenyl moieties, constituting a ketene acetal system, we were interested in the biosynthesis of this compound. M e 0 M e O @ o a o ,

The biosynthesis of shikimate metabolites

“…Feeding experiments in CuC1,-treated seedlings of red clover (Trifoliurn pratense), using ,C-and 2H-labelled 2',4,4'-trihydroxychalcone, confirmed that the rearrangement process in the biosynthesis of isoflavonoids was an intramolecular migration of an aryl Thus, the [ I 3C,]trihydroxychalcone (74) was transformed into the labelled isoflavone formononetin (75) and the corresponding labelled pterocarpan phytoalexins medicarpin (76) and maackiain (77) with retention of the intact 3C-1 3C linkages (Scheme 23), demonstrating the aryl migration. The intramolecular nature of the migration was proved by the isolation of 2H3-labelled formononetin and medicarpin after feeding the [2H3]chalcone (78) to the plants, as shown by mass-spectral analysis.…”

Ageratum conyzoides L. for the management of pests and diseases by small holder farmers

“…The species produces a diversity of compound classes with examples of those most reported presented in Figure 1. Conyzorigum, a cromene was identified by Vyas and Mulchandani (1984) while Borthakur and Buruah (1987) identified Precocene I and II. In addition to Precocene I and II, Ekundayo et al (1988) identified 51 terpenoid compounds in the whole plants.…”

Synthesis, Spectroscopic Analysis and Assessment of the Biological Activity of New Hydrazine and Hydrazide Derivatives of 3-Formylchromone

“…Due to the increasing problem of drug resistance, the search for novel and efficient antimicrobial and antiproliferative agents is a worldwide concern. Benzopyrones occur widely in Nature, and benzopyrone derivatives have been reported in algae [ 1 ], fungi [ 2 , 3 ] and plants [ 4 , 5 ] including trees [ 6 , 7 ]. These compounds show broad pharmacological activities, and studies have found them to have antimicrobial, antitumor, antioxidant, anti-HIV and antiallergenic properties [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ].…”