Salix triandra L. (S. armena Schischk., S. medwedewii Dode, S. subgragilis auct., S. amygdalina L.)

Antiproliferative Flavanoid Dimers Isolated from Brazilian Red Propolis

“…Propolones ( 1 – 4 ), propolonones ( 5 , 6 , and 7 ), and propolol ( 8 ) skeletons have the C-3 B-ring equatorially oriented, as it can be verified by analysis of coupling constants assigned to the − O -CH 2 –CH–CH 2 – moiety (Tables –), a feature observed for other isoflavans as well. , The small value of the specific rotation recorded for metabolites 1 – 8 suggested that they were isolated as scalemic mixtures, since pure enantiomers of related compounds usually show high [α] D values. − Chiral-phase HPLC analysis of 1 – 8 was attempted with several chiral columns (Chiralpak AD-H, Chiralcel OD-H, Chiralcel OJ-H, and Phenomenex OD-H). However, only the Chiralpak AD-H column provided partially satisfactory results, since the enantiomers of 1 , 2 , 5 , and 6 could not be completely resolved.…”

“…The first fragment consisted of a 1,2,4,5-tetrasubstituted and a 1,2,4-trisubstituted benzene moiety. NMR data (Table ) indicated a heterocyclic ABMXY spin system comprising the O -CH 2 –CH–CH 2 – moiety, characteristic of an isoflavan. , This assignment was supported by the H-2α/H-2β, H-2α/H-3 and H-3/H-4 1 H– 1 H COSY correlations, along with the HMBC cross-peaks from H-2α and H-2β to C-3 (δ C 33.4), C-4 (δ C 31.5), and C-8a (δ C 157.5) and from H-4 to C-3, C-4a (δ C 115.6), C-8a, and C-1′ (δ C 121.4) (Figure ).…”

“…This aromatic portion was joined to the O -CH 2 –CH–CH 2 fragment based on the HMBC cross-peaks from CH 2 -2 to C-3, C-4, C-8a, and C-1′ (δ C 120.1); from H-3 to C-4a, C-1′, and C-2′ (δ C 155.4); and from H-4 to C-3, C-4a, and C-1′. The fused aromatic − O -CH 2 –CH–CH 2 system clearly constituted an isoflavan moiety, , confirmed by analysis of the HMBC spectrum, that showed correlations from H-3′ (δ H 6.38) to C-1′, C-2′, and C-5′ (δ C 118.9) as well as from H-6′ (δ H 6.70) to C-3, C-4′ (δ C 155.5), and C-5′.…”

“…Analysis of the 1 H, 13 C, and HSQC NMR spectra of 5 showed three sp 3 methylene groups at δ H 3.81/4.30 (δ C 71.4, CH 2 -2), δ H 2.76/2.72 (δ C 31.2, CH 2 -4), and δ H 3.86 (δ C 24.8, CH 2 -8″) as well as an sp 3 methine at δ H 3.43 (δ C 33.1, CH-3). The COSY spectrum of 5 showed that the spin system − O -CH 2 –CH–CH 2 – comprised of CH 2 -2, CH-3, and CH 2 -4, typical of isoflavans. , Signals for two methoxy groups were observed at δ H 3.74 (s, δ C 55.8, OCH 3 -7) and 3.84 (s, δ C 56.4, OCH 3 -6″). The 1 H and 13 C NMR spectra also indicated the presence of a 2,3,6-substituted benzofuran moiety based on the characteristic hydrogen signals at δ H 7.19 (d, J = 8.6 Hz; δ C 121.2, CH-4″), δ H 6.77 (dd, J = 8.6 and 2.2 Hz; δ C 112.1, CH-5″), and δ H 7.07 (d, J = 2.2 Hz; δ C 96.8, CH-7″), while the 13 C resonances at δ C 151.5 (C-2″) and δ C 115.9 (C-3″) indicated a furan moiety.…”

“…Flavanoid dimers are rare in nature . A small series of isoflavanoid dimers have been reported since their discovery by Ferreira’s group in 1988. − Recently, sphenostylisins A–K were reported from the root bark of Sphenostylis marginata ssp.…”