Apigenin 4′-O-β-d-glucoside 7-O-β-d)- glucuronide: The copigment in the blue pigment of Centaurea cyanus

The copigment present in the crystalline blue pigment isolated from Blue Boy cornflowers (Centaurea cyanus L.) was identified as apigenin 4′-O-β-glucoside 7-O-β-d-glucuronide. The NMR spectra of aryl glucuronides are discussed.     

Sulphuretin glycosides of Coreopsis mutica

The anthochlor complement of Coreopsis mutica has been determined. The compounds observed were all glycosidic derivatives of sulphuretin, being the mono- and di-glucosides and two new glucosidic derivatives acylated with caffeic acid.     

Ludalbin,a new lactone from Artemisia ludoviciana

Artemisia ludoviciana Nutt. ssp. albula (Woot.) Keck, a member of the vulgaris complex, contains a sesquiterpene lactone, ludalbin, which is 8-α-acetoxydouglanine.     

8,6-Hydroxy dehydrozaluzanin C from Andryala pinnatifida

The roots of Andryala pinnatifida afforded 8β-hydroxy dehydrozaluzanin C.     

1H NMR Spectroscopy of pyrrolizidine alkaloids

The ¹H NMR spectra of three pyrrolizidine alkaloids of the macrocyclic diester type, retrorsine, seneciphylline and senecionine, plus their three N-oxides have been assigned. Previous ¹H NMR studies of these pyrrolizidine alkaloids have stressed the difficulties of spectral intrepretation. The results reported here will provide a useful resource for analysis of tertiary structure in these and related compounds.     

Dimeric chromenes and mixed dimers of a chromene with euparin from Encelia canescens

The investigation of Encelia canescens afforded, in addition to several known compounds, four new dimeric p-hydroxyacetophenone derivatives, two epimeric chromene dimers and two epimeric mixed dimers of euparin and encecalin. Furthermore, derivatives of tremetone and of encecalin were present. The structures were elucidated hy high field ¹H NMR spectroscopy.     

The flavonoids of Megalodonta beckii and isolation of 2′-3-Dihydroxy-4-methoxy-4′-glucosyl chalcone

A new naturally occurring chalcone glycoside, $\text{2′,-}\text{dihydroxy}\text{-4-}\text{methoxy}\text{-4′-O-β-}\text{d}\text{-}\text{glucosyl}$ chalcone, and other chalcones, aurones, flavonols, and anthocyanins are reported from Megalodonta (Bidens) beckii. The plan is an amphibious aquatic with heterophyllous leaves, but the presence of certain flavonoids is correlated with vegetative versus floral tissues rather than vegetative leaf form. The implications of flavonoid chemistry with respect to the relationship of M. beckii to several sections of Bidens are discussed.     

Flavonoid diversity and endemism in Arnica subgenus Austromontana

Eighty-seven populations, representing eight species of Amica subgenus Austromontana, were examined for flavonoids. A total of 22 compounds, including simple and methylated flavone and flavonol glycosides as well as methylated aglycones, were isolated and identified. The two widespread species, A. cordifolia and its presumed early derivative A. latifolia, are ancestral species of the subgenus. From these two species, major evolutionary diversification within the subgenus has taken place largely in the Klamath region of Oregon and California, resulting in the formation of several rare, endemic species. These endemics are generally characterized by reduced flavonoid profiles and/or an increase in the number of methylated aglycones while, in contrast, the wider ranging species have few methylated aglycones and more glycosides. However, one species, A. viscosa, a rare volcanic endemic, exhibits the most elaborate and specialized flavonoid profile within the subgenus.     

Two new flavone glycosides from Cirsium lineare

An examination of four species of Cirsium disclosed the presence of two new flavonoids in C. lineare. The structure of one was 5,4′-dihydroxy-6,7,3′-trimethoxyflavone (cirsilineol) 4′-monoglucoside and the other 5,3′,4′-trihydroxy-6,7-dimethoxyflavone (cirsiliol) 4′-monoglucoside. Luteolin 7-glucoside was found in C. suffultum, and pectolinarin and linarin in C. kamtschaticum and C. pectinellum.