Derrisrobustones A-D, isoflavones from the twig extract of Derris robusta (DC.) Benth. and their α-glucosidase inhibitory activity

The potentiality of isoflavones from Derris robusta (DC.) Benth. against α-glucosidase

The four recently described isoflavones, derrisrobustones A-D, and eight known isoflavones extracted from Derris robusta (DC.) Benth. (Leguminosae) were identified as potential isoflavones for α-glucosidase inhibitory activity. However, the inhibitory ability of each isoflavone was quite different and the structural and dynamical properties of the isoflavones in the binding with α-glucosidase have not been studied. In this study, the molecular dynamics (MD) simulation and the molecular mechanics generalized Born surface area (MM/GBSA) methods were applied to gain insight into isoflavones bound with the α-glucosidase active site. The results found that the isoflavones with a hydroxy substituent could be stabilized in the α-glucosidase active site with low values of the binding free energy, especially derrisrobustone D and derrubone. The isoflavones, except for derrubone, were bound with α-glucosidase by means of electrostatic force effectively.

Synthesis and Bioactivity of Isoflavones from Ficus carica and Some Non-Natural Analogues

Ficucaricone D (1) and its 4'-demethyl congener 2 are isoflavones isolated from fruits of Ficus carica that share a 5,7-dimethoxy-6-prenyl-substituted A-ring. Both natural products were, for the first time, obtained by chemical synthesis in six steps, starting from 2,4,6-trihydroxyacetophenone. Key steps are a microwave-promoted tandem sequence of Claisen- and Cope-rearrangements to install the 6-prenyl substituent and a Suzuki-Miyaura cross coupling for installing the B-ring. By using various boronic acids, non-natural analogues become conveniently available. All compounds were tested for cytotoxicity against drug-sensitive and drug-resistant human leukemia cell lines, but were found to be inactive. The compounds were also tested for antimicrobial activities against a panel of eight Gram-negative and two Gram-positive bacterial strains. Addition of the efflux pump inhibitor phenylalanine-arginine-β-naphthylamide (PAβN) significantly improved the antibiotic activity in most cases, with MIC values as low as 2.5 μM and activity improvement factors as high as 128-fold.

Structural modification of olibergin A, an isoflavonoid, from Dalbergia stipulacea Roxb. and its cytotoxicity

Fifteen derivatives were synthesized from olibergin A, a major isoflavonoid isolated from the stems of Dalbergia stipulacea Roxb. All compounds were evaluated for cytotoxicity against HCT-116, HT-29, MCF-7 and vero cell lines using MTT assay. Cytotoxicity results showed 5-hydroxy-7,2',4',5'-tetramethoxyisoflavone (5) was the most active with IC₅₀ values of 19.03 ± 0.70, 10.83 ± 1.65, 12.53 ± 0.70 and 13.53 ± 0.84 μM against HCT-116, HT-29, MCF-7 and vero cell lines, respectively. It should be noted that 5-hydroxy-7,2',4',5'-tetramethoxyisoflavone (5) showed two times less toxicity against vero cells than the cisplatin standard (IC₅₀ = 6.55 ± 0.81 μM) while 5 and cisplatin exhibited nearly equal cytotoxicity against the MCF-7 cell line. 5,7,2',4',5'-Pentamethoxyisoflavanone (10) showed an IC₅₀ value of 30.34 ± 1.15 μM against the HCT-116 cell line and exhibited weak cytotoxicity against normal cells, the vero cell line. In addition, 5,7,4'-trihydroxy-2',5'-dimethoxyisoflavan oxime (13) demonstrated cytotoxicity against HT-29 cells with an IC₅₀ value of 31.41 ± 1.38 μM and displayed weak activity toward the vero cell line. The information revealed that these compounds were suitable for development to anticancer agents against HCT-116, HT-29 and MCF-7 cell lines.