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Broussonins A and B, new phytoalexins from diseased paper mulberry

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Abstract

Isolation and structure elucidation of two phytoalexins (1 and 2), produced by diseased paper mulberry and designated as broussonins A and B, are described. These phytoalexins are characterized structurally by a 1,3-diphenylpropane skeleton.

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... 10 1,3-Diarylpropanes, homologues to dihydrostilbenes and a subclass of flavonoids (C6-C3-C6 unit) are also an important secondary metabolites of plants and exhibit diverse biological activities viz. antifungal, 11 anti-inflammatory, 12 anticancer, 13 antiadipogenic, 14 antitubercular, 13a and antimalarial, 15 to name a few. 1,3-Diarylpropanes attached with anthranilic acid were also investigated as b-amyloid aggregation inhibitors in Alzheimer's disease. ...
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An efficient synthesis of dihydrostilbenes (1-5) and diarylpropanes (6-10) is achieved from the commercially available starting materials and Wittig-Horner reaction, Claisen-Schmidt condensation and hydrogenation as key steps. Later, their nitric oxide (NO) production inhibition effects were evaluated in lipopolysaccharide (LPS)-induced RAW-264.7 macrophages as an indicator of anti-inflammatory activity. All the tested compounds significantly decreased NO production in a concentration-dependent manner except compounds 2, 6 and 8 and did not show notable cytotoxicity except compound 1. Two compounds i.e., compound 9 (hindsiipropane B) (100%; IC50 = 1.84 μM) possessed the most potent NO inhibitory activity which was even stronger than the positive control, L-NMMA (90.1%; IC50 = 2.73 μM) followed by compound 4 (75.5%; IC50 = 2.98 μM) at 10 μM concentration and this finding was also further correlated by suppressed expression of LPS stimulated inducible NO synthase. Our study revealed that compound 9, a 1,3-diarylpropane scaffold with 3“,4”-dimethoxyphenyl and 3’,4’-dihydroxy 2’-methoxyphenyl motifs could be considered as potential compound or lead compound for further development of NO production-targeted anti-inflammatory agents.
... The 23 known flavonoids were identified as daphnegiravone D (4) (Wang et al., 2017), 5,7,3,4-tetrahydroxy-3-methoxyflavone (5) (Zheng et al., 2008), 8-prenylquercetin-3-methyl ether (6) (Lou et al., 2019), uralenol-3-methyl ether (7) (Jia et al., 1993), isolicoflavonol (8) (Zheng et al., 2008), broussoflavonol F (9) (Fang et al., 1995), glycyrrhiza-flavonol A (10) (Hatano et al., 1997), broussoflavonol A (11) (Matsumoto et al., 1985), diosmetin (12) (Cai et al., 2000), ()-liquiritigenin (13) (Hu et al., 2010), ()-bavachin (14) (Chen et al., 2005), cathayanon H (15) (Ni et al., 2010), (2S)-7,4-dihydroxyflavan (16) (Achenbach et al., 1988), (2S)-7,3'-dihydroxy-4'-methoxyflavan (17) , (2S)-7,4-dihydroxy-3-prenylflavan (18) (Lee et al., 2001), kazinol B (19) (Li et al., 2010), daphnegiravan H (20) (Sun et al., 2016), 4,2,4-trihydroxychalcone (21) (Achenbach et al., 1988;Veitch et al., 2003), 4,4-dihydroxy-2-methoxychalcone (22) (Achenbach et al., 1988;Fu et al., 2008), broussochalcone A (23) (Ryu et al., 2012), 1-(4-hydroxy-2-methoxyphenyl)-3-(3-hydroxy-4-methoxyphenyl)-propane (24) (Garcez et al., 2006), 1-(2-hydroxy-4-methoxyphenyl)-3-(4-hydroxy-3-methoxyphenyl)-propane (25) (Martinez V and Cuca S, 1987), 1-(4-hydroxy-2-methoxyphenyl)-3-(4-hydroxyphenyl)-propane (26) (Jo et al., 2015;Takasugi et al., 1980) by comparing their spectroscopic data with those in the literature. The types of these 26 compounds were flavonols (1, 2, and 411), flavone (12), dihydroflavones (13 and 14), dihydroflavonol (15), flavans (3 and 1620), chalcones (2123), and 1,3-diarylpropanes (2426). ...
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The stem and root barks of Daphne giraldii Nitsche, also known as “Zushima”, is a traditional Chinese medicine with a long history of treating a variety of diseases such as rheumatism arthralgia, quadriplegia, headache, stomachache, waistache, and bruises. Chromatographic fractionation of the EtOH extracts of “Zushima” has led to the isolation of 26 flavonoids, including ten flavonols (1, 2, and 4−11), one flavone (12), two dihydroflavones (13 and 14), a dihydroflavonol (15), six flavans (3 and 16−20), three chalcones (21−23), and three 1,3-diarylpropanes (24−26). Daphgiflavones A−C (1−3) were new flavonoids. Their structures were elucidated by spectroscopic analysis. All compounds were evaluated for anti-inflammatory properties by testing their inhibitory activities against nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophages. Compounds 8, 11, 21, and 23 exhibited significant inhibition on NO production with IC50 values ranging from 2.26 to 6.88 μM, being more active than the positive control quercetin (IC50: 14.16 μM).
... The location of the three oxygen functions on the benzene ring was deduced from HMBC correlations; thus, cross-peaks were observed between methylene protons (δ 2.57; H 2 -1) and C-2, C-3, C-2 0 , and C-6 0 , methoxyl protons and C-2 0 , H-6 0 and C-2 0 and C-4 0 , H-5 0 and C-1 0 and C-3 0 . These data closely resembled those of broussonin A and B (phytoalexins with a 1,3-diarylpropane carbon skeleton) isolated from Broussonetia papyrifera except for the appearance of the signals due to a monosubstituted benzene ring instead of a para-substituted benzene ring (14). Therefore, the structure of 1 was established as 1-(3 0 ,4 0 -dihydroxy-2 0 -methoxyphenyl)-3-(phenyl)propane (1). ...
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