Isoflavonoids from roots of Erythrina zeyheri

Uncommon 5‐Methoxyisoflavans from Desmodium canum

“…The mass fragmentation pattern (b, c and related ions) and the 1 Hand 13 C NMR spectroscopic data (Table S2) of 4 and 5 reveal that the substitution pattern of the B rings is the same as those of 2 and 3 and involves a methoxy and a phenolic hydroxy group located in the 2Ј-and 4Ј-positions, respectively. The relative positions (2Ј-OMe and 4Ј-OH) were assigned on the basis of the following considerations: (1) a negative Gibbs test: the position para to the hydroxy group is not free, [6] (2) the H-3Ј signal appears in a highfield environment in the 1 H NMR spectrum relative to the H-5Ј signal as in 2Ј-OMe, 4Ј-OMe [7] and 2Ј-OMe, 4Ј-OH [8] substituted isoflavonoid B rings; the opposite is true for 2Ј-OH, 4Ј-OH [7] and 2Ј-OH, 4Ј-OMe [9,10] substitutions, (3) comparable shifts (+0.40 versus +0.38 ppm) were obtained in the 1 H NMR spectra in C 5 D 5 N for the H-3Ј and H-5Ј signals; the values are both typical of protons ortho to a free phenolic group, [11] (4) the C-3Ј resonance (at δ = 99 ppm) is in agreement with a 2Ј-OMe, 4Ј-OH substitution, whereas a 2Ј-OH, 4Ј-OMe substitution would require a value of 103 ppm. [8] Analogously C-1Ј appears at δ = 116 ppm (2Ј-OH) instead of 120 ppm (2Ј-OMe).…”

Prenylated Flavonoids with PTP1B Inhibitory Activity from the Root Bark of Erythrina mildbraedii

“…The observations of aliphatic protons at H-2 ax , H-2 eq , H-3, H-4 ax , and H-4 eq in the 1 H-NMR spectrum, along with carbon signals assigned for C-2, C-3, and C-4 in the 13 C-NMR spectrum, suggested that 3 was an isoflavan. 19,20) The 1 H-NMR spectrum displayed three aromatic protons of an ABX spin system (H-5, H-6, H-8), a dimethylpyran ring (H-3ٞ, H-4ٞ), two methyl groups (d H 1.41, 6H, s), and a prenyl group (H-1Љ, H-2Љ, H-4Љ, H-5Љ). The HMBC correlations ( Fig.…”

“…The absolute configuration of 3 was determined to be 3R by analysis of its circular dichroism (CD) data. 19,20) Thus the structure of compound 3 was de-…”

Cytotoxic flavonoids from Erythrina caffra Thunb

“…The genus Erythrina belongs to the family Fabaceae comprising over 110 species distributed in tropical and sub-tropical regions in both the southern and the northern hemispheres of the world as well as in some temperate regions of the world [1]. Erythrina caffra, the coast coral tree, is a tree native to south eastern Africa.…”