Enantioselective syntheses of both enantiomers of 9'-dehydroxyimperanene and 7,8-dihydro-9'-dehydroxyimperanene and the comparison of biological activity between 9-norlignans and dihydroguaiaretic acids

Cytotoxicity Activity of Some meso-Dihydroguaiaretic Acid Derivatives and Mode of Action of the Most Active Compound

The aim of this study was to screen sixteen meso-1 semi-synthetic derivatives bearing ether, esther, carbamate, phosphate or aminoether functional groups against five cancer cell lines: MCF-7 (breast), A549 (lung), HepG2 (liver), HeLa (cervix), and DU145 (prostate) at 25 μM using the MTT assay. Results from the screening showed that two derivatives had the lowest percentage of cell viability at 25 μM, the aminoether derivative meso-11 and the esther derivative meso-20 against A549 (44.15±0.78 %) and MCF-7 (41.60±0.92 %), respectively. Then, it was determined the IC50 value of each compound against their most sensitive cancer cell line. Results showed that aminoether derivative meso-11 showed potent cytotoxicity against A549 (IC50 =17.11±2.11 μM), whereas it resulted more cytotoxic against the LL-47 lung normal cell line (IC50 =9.49±1.19 μM) having a Selective Index (SI) of 0.55. On the other hand, the esther derivative meso-20 exhibited potent activity against MCF-7 (IC50 =18.20±1.98 μM), whereas it displayed moderate cytotoxicity against the MCF-10 breast normal cell line (IC50 =41.22±2.17 μM) with a SI of 2.2. Finally, studies on the mechanism of action of meso-20 indicated disruption of MCF-7 plasma membrane in vitro and the AMPK activation in silico.

The enantioselective total syntheses of (+)-7-oxohinokinin, (+)-7-oxoarcitin, (+)-conicaol B and (-)-isopolygamain

A flexible approach to C7 keto dibenzyl butyrolactone lignans was developed and the synthesis of several natural products and their related derivatives is described herein. The developed pathway proceeds through enantioenriched β-substituted butyrolactones, from which facile aldol addition and subsequent oxidation affords the desired benzylic ketone moiety. This methodology was used to complete the first enantioselective total syntheses of three natural products, (+)-7-oxohinokinin, (+)-7-oxoarcitin and (+)-conicaol B, and a further five analogues. The utility of this method was further demonstrated through a 1-2 step modification to access another class of natural product, aryltetralin lignans, allowing the asymmetric total synthesis of (-)-isopolygamain and a polygamain derivative. Anti-proliferative testing determined (-)-isopolygamain was the most active of the compounds prepared, with IC₅₀ values of 2.95 ± 0.61 μM and 4.65 ± 0.68 μM against MDA-MB-231 (triple negative breast cancer) and HCT-116 (colon cancer) cell lines, respectively.

Design of 92 New 9-Norlignan Derivatives and Their Effect on Cell Viabilities of Cancer and Insect Cells

Ninety-two new 9-norlignan derivatives containing more effective compounds against both cancer and insect cells than lead compounds were synthesized. Against HeLa cells, 7-(3,4-dimethoxyphenyl)-7'-(3'-hydroxy-4'-methoxyphenyl) derivative 63 (IC₅₀ = 0.9 ± 0.2 μM) was to be around 6-fold more potent than lead compound 5. Moreover, against HL-60 cells, 7-(4-trifluoromethylphenyl)-7'-(3'/4'-hydroxyphenyl) derivatives 78 and 79 (IC₅₀ = 2.2 ± 0.4 μM and 2.4 ± 0.6 μM) were 3-fold more potent than lead compound 5. Furthermore, against Sf9 cells from the common cutworm, the 7-(4-trifluoromethylphenyl) derivatives bearing electron-withdrawing groups 76-96 showed a wider range of activity (around 20-fold difference), giving valuable information on the structure-activity relationship. The 7-(4-trifluoromethylphenyl)-7'-(2'/3'-hydroxyphenyl) derivatives 77 and 78 (IC₅₀ = 4.7 ± 0.6 μM and 4.9 ± 0.9 μM) had around 2-fold higher activity against Sf9 cells than lead compound 5. The 7-(4-trifluoromethylphenyl)-7'-(3'-hydroxyphenyl) derivative 78 was also effective against mosquito NIAS-AcAl-2 cells with an IC₅₀ value of 5.4 ± 0.3.

9-Norlignans: Occurrence, Properties and Their Semisynthetic Preparation from Hydroxymatairesinol

Lignans, neolignans, norlignans and norneolignans constitute a large class of phenolic natural compounds. 9-Norlignans, here defined to contain a β⁻β' bond between the two phenylpropanoid units and to lack carbon number 9 from the parent lignan structure, are the most rarely occurring compounds within this class of natural compounds. We present here an overview of the structure, occurrence and biological activity of thirty-five 9-norlignans reported in the literature to date. In addition, we report the semisynthetic preparation of sixteen 9-norlignans using the natural lignan hydroxymatairesinol obtained from spruce knots, as starting material. 9-Norlignans are shown to exist in different species and to have various biological activities, and they may therefore serve as lead compounds for example for the development of anticancer agents. Hydroxymatairesinol is shown to be a readily available starting material for the preparation of norlignans of the imperanene, vitrofolal and noralashinol family.

Effects of Substituents on the Aromatic Ring of Lignano-9,9'-lactone on Plant Growth Inhibitory Activity

The relationship between the structure of lignano-9,9'-lactone (2,3-dibenzylbutyrolactone) and its activity as a plant growth regulator has been clarified. Derivatives with higher plant growth inhibitory activity than natural dimethylmatairesinol 4 were synthesized. The 2-hydroxy-7- Z-ene derivative 42 displayed growth inhibitory activity against both the shoots (IC50 = 0.65 mM) and roots (IC50 = 0.43 mM) of lettuce seedlings. Regiospecific activity was observed. The 2,3-dihydroxy derivative 24 showed the highest growth inhibitory activity against both the shoots (IC50 = 0.36 mM) and roots (IC50 = 0.13 mM) of Italian ryegrass seedlings. A similar level of activity to 24 against just the roots of Italian ryegrass seedlings was maintained when the hydroxy group at position 3 of the 2,3-dihydroxy derivative 24 was replaced by a fluorine atom. The (2-hydroxy,4-fluoro)-derivative 33 also showed growth inhibitory activity against both the shoots (IC50 = 0.79 mM) and roots (IC50 = 0.14 mM) of Italian ryegrass seedlings. The level of activity was found to depend on the positions of the two hydroxy groups or the hydroxy group and fluorine atom on the aromatic ring. The importance of the lignano-9,9'-lactone structure was also shown.