Two New Homoisoflavonoids from the Bulbs of Bessera elegans

Abstract

A further chemical investigation of the bulbs of Bessera elegans (Liliaceae) led to the isolation of a new homoisoflavonoid (1), a new scillascillin-type homoisoflavonoid (2), three known flavonoids (3-5), and two known norlignans (6 and 7). The structures of the new homoisoflavonoids (1 and 2) were determined based on the results of extensive spectroscopic analysis, including two-dimensional NMR data. The isolated compounds (1-7) were evaluated for cytotoxicity against HL-60 human promyelocytic leukemia cells and TIG-3 normal human diploid fibroblasts. Compound 1 exhibited potent tumor-selective cytotoxic activity against HL-60 cells.

Spiro-Flavonoids in Nature: A Critical Review of Structural Diversity and Bioactivity

“… Family Plant Part Compound References Asparagaceae Bessera elegans Schult.f. bulbs 57 [ 13 ] Chionodoxa luciliae Boiss. bulbs 49–52 [ 14 ] Drimiopsis barteri Baker bulbs and leaves 50, 56, 60, 61, 64 [ 15 ] Drimiopsis burkei Baker bulbs 53, 62 [ 15 ] Drimiopsis maculata Lindl.…”

“…However, the presence of the spiro-ring rendered the tested scillascillin-type homoisoflavonoids completely inactive, regardless of the substituents in the A and B rings. Likewise, Matsuo et al (2014) [ 13 ] evaluated (3 R )-5,7-dihydroxy-6-methyl-3-(3′-hydroxy-4′-methoxybenzyl)chroman-4-one and compound 57 (isolated from Bessera elegans ), which differed only in the presence of the 3- spiro -cyclobutene ring (formed by the coupling of C-3 and C-2′ carbons), for cytotoxicity against human HL-60 promyelocytic leukemia cells and normal human diploid TIG-3 fibroblasts. The homoisoflavonoid without the cyclobutene ring showed a potent tumor-selective cytotoxic activity against HL-60 cells, while 57 was noncytotoxic (and noncytotoxic against TIG-3).…”

“…On the other hand, 3 J HC , similar to 3 J HH , follows the Karplus relation and can also be used to determine additional constraints on dihedral angles-the values of this constant are lower (1-3 Hz) for gauche than for anti-periplanar conformation (5-8 Hz) [31,[67][68][69]. An empirical rule developed by Nakashima et al (2016) [11], which allows easy determination of the relative configuration for the spiro-carbon (C-3) and its neighboring carbon (C-2), was applied on the basis of the observation of 13 C NMR chemical shifts for some spiro-flavonoids (abiesinols A-H, yuccalides A-C, yuccaols A-E, and gloriosaols A-E) reported in this review. Namely, for the 13 C NMR shifts measured in the acetone-d 6 and methanol-d 4 , the γ-lactone carbonyl group (C-4) located in the δ C range of 174.6-176.9 indicates a syn-relationship between C-4 and the aromatic substituent located at the C-2 carbon, due to the anisotropic shielding effect exerted by the aromatic substituent on C-4, and thus the rel-(2R,3S) configuration.…”

“…An empirical rule developed by Nakashima et al (2016) [11], which allows easy determination of the relative configuration for the spiro-carbon (C-3) and its neighboring carbon (C-2), was applied on the basis of the observation of 13 C NMR chemical shifts for some spiro-flavonoids (abiesinols A-H, yuccalides A-C, yuccaols A-E, and gloriosaols A-E) reported in this review. Namely, for the 13 C NMR shifts measured in the acetone-d 6 and methanol-d 4 , the γ-lactone carbonyl group (C-4) located in the δ C range of 174.6-176.9 indicates a syn-relationship between C-4 and the aromatic substituent located at the C-2 carbon, due to the anisotropic shielding effect exerted by the aromatic substituent on C-4, and thus the rel-(2R,3S) configuration. On the other hand, the γ-lactone carbonyl group, which has an anti-relationship with the aromatic substituent in C-2, has chemical shifts in the range δ C 178.6-181.1, indicating a rel-(2R,3R) configuration.…”

A Comprehensive Review on Chemotaxonomic and Phytochemical Aspects of Homoisoflavonoids, as Rare Flavonoid Derivatives

“…A methanolic bulb extract of Bessera elegans turned out to contain novel HIFs, including (3 R )-5,7-dihydroxy-6-methyl-3-(3′-hydroxy-4′-methoxybenzyl)chroman-4-one and a rare derivative containing a scillascillin-type skeleton, (3 R )-5,7,3′-trihydroxy-4′-methoxy-6-methylspiro[2H-1-benzopyran-7′-bicyclo[4.2.0]octa[1,3,5]-trien]-4-one. Silica gel (eluting system: CHCl 3 –MeOH–H 2 O 100:10:1) and RP CC (H 2 O–MeOH 1:2) were employed as separation instruments [ 79 ].…”