Antiviral Flavans from the Leaves of Pithecellobium clypearia

Leung, Kam Tong; Yao, Fenghe; Ooi, Linda S. M.; Ooi, Vincent E.C.

doi:10.1021/np050498o

Cited by 61 publications

(35 citation statements)

References 8 publications

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“…As shown in Table 3, (10) showed potent anti-RSV activity comparable to the positive drug ribavirin. In our previous studies, we have found that caffeoyl acid derivatives from natural medicines had potent anti-RSV activities [36,[38][39][40]. Compound 10 is a flavonoid glycoside with a cis-coumaroyl connection.…”

Section: Anti-rsv Activitiesmentioning

confidence: 99%

Phenolic Compounds from the Flowers of Bombax malabaricum and Their Antioxidant and Antiviral Activities

Zhang

et al. 2015

Molecules

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Abstract:Three new phenolic compounds 1-3 and twenty known ones 4-23 were isolated from the flowers of Bombax malabaricum. Their chemical structures were elucidated by spectroscopic analyses (IR, ESI-MS, HR-ESI-MS, 1D-and 2D-NMR) and chemical reactions. The antioxidant capacities of the isolated compounds were tested using FRAP and DPPH radical-scavenging assays, and compounds 4, 6, 8, 12, as well as the new compound 2, exhibited stronger antioxidant activities than ascorbic acid. Furthermore, all of compounds were tested for their antiviral activities against RSV by the CPE reduction assay and plaque reduction assay. Compounds 4, 10, 12 possess in vitro antiviral activities, and compound 10 exhibits potent anti-RSV effects, comparable to the positive control ribavirin.

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Section: Anti-rsv Activitiesmentioning

confidence: 99%

Phenolic Compounds from the Flowers of Bombax malabaricum and Their Antioxidant and Antiviral Activities

Zhang

et al. 2015

Molecules

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“…In a strain of S. cerevisiae containing and overexpressing C. albicans MDR1 , they found a 35-fold decrease in FLU MICs (300–8.5 μM) when ECTA was co-applied. Another group of triterpenoid inhibitors of efflux pump activity identified later by this group was the capisterones (Li et al, 2006). These compounds were isolated from the marine green alga, Penicillus capitatus .…”

Section: Chemosensitization Of Antifungal Agentsmentioning

confidence: 99%

Chemosensitization as a Means to Augment Commercial Antifungal Agents

2012

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Antimycotic chemosensitization and its mode of action are of growing interest. Currently, use of antifungal agents in agriculture and medicine has a number of obstacles. Foremost of these is development of resistance or cross-resistance to one or more antifungal agents. The generally high expense and negative impact, or side effects, associated with antifungal agents are two further issues of concern. Collectively, these problems are exacerbated by efforts to control resistant strains, which can evolve into a treadmill of higher dosages for longer periods. This cycle in turn, inflates cost of treatment, dramatically. A further problem is stagnation in development of new and effective antifungal agents, especially for treatment of human mycoses. Efforts to overcome some of these issues have involved using combinations of available antimycotics (e.g., combination therapy for invasive mycoses). However, this approach has had inconsistent success and is often associated with a marked increase in negative side effects. Chemosensitization by natural compounds to increase effectiveness of commercial antimycotics is a somewhat new approach to dealing with the aforementioned problems. The potential for safe natural products to improve antifungal activity has been observed for over three decades. Chemosensitizing agents possess antifungal activity, but at insufficient levels to serve as antimycotics, alone. Their main function is to disrupt fungal stress response, destabilize the structural integrity of cellular and vacuolar membranes or stimulate production of reactive oxygen species, augmenting oxidative stress and apoptosis. Use of safe chemosensitizing agents has potential benefit to both agriculture and medicine. When co-applied with a commercial antifungal agent, an additive or synergistic interaction may occur, augmenting antifungal efficacy. This augmentation, in turn, lowers effective dosages, costs, negative side effects and, in some cases, countermands resistance.

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“…Aer purication by ash silica gel column chromatography, compound 9 (0.62 g) was obtained as a white solid in 99.0% yield. 1 Synthesis of (AE)-7-O-galloyltricetiavan (1a). Compound 9 (0.48 g, 0.88 mmol) was dissolved in dry CH 2 Cl 2 (20 mL), then BBr 3 (15.4 mL, 1.0 M in CH 2 Cl 2 ) was added dropwise at À40 C.…”

Section: General Experimental Proceduresmentioning

confidence: 99%

“…Aer purication by silica gel column chromatography, compound 11 (110 mg) was obtained as a colorless oil in 93% yield. 1 …”

Section: General Experimental Proceduresmentioning

confidence: 99%

A concise synthesis of (±)-7-O-galloyltricetiflavan

et al. 2018

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(AE)-7-O-galloyltricetiflavan (1a) was synthesized successfully in five steps from the commercially available trihydroxyacetophenone (2) and trimethoxybenzoyl chloride (3). The flavone 4a was prepared in a one-pot reaction and it gave hex-O-methylflavan 6 followed by acylation and reduction. However, the demethylation of flavan 6, 5-O-acetylflavan 10 and 5-O-phenylacetylflavan 11 by BBr 3 gave all the hydrolyzed fragments 7 and 8 as the major products. By contrast, in the same condition, hept-Omethylflavan 9 could provide the desired product (AE)-7-O-galloyltricetiflavan (1a) in 91% yield. The additional 5-O-B-Br 2 complex may stabilize the ester bond during the demethylation process.(À)-7-O-Galloyltricetiavan (1, Fig. 1) was isolated from a methanolic extract of the leaves of Pithecellobium clypearia by Ooi V. and coworkers in 2006.1 It is a catechin-like compound without an OH substituent at C-3, and it shows good antiviral activities against respiratory syncytial virus (RSV), inuenza A (H1N1) virus, coxsackie B3 (Cox B3) virus and herpes simplex virus type 1 (HSV-1) as well as anti-inammatory and anti-allergic activities.2-5 To date, the preparation of (À)-7-O-galloyltricetiavan (1) still requires extraction and purication of plant material, and only a few synthetic examples of this type of avan have been reported.6,7 Herein we report the rst total synthesis of (AE)-7-Ogalloyltricetiavan (1a) in ve steps as well as an interesting discovery during the demethylation process.The synthesis of (AE)-7-O-galloyltricetiavan (1a) was started from the preparation of the avone derivative 4a as shown in Scheme 1. Buckle's group reported an efficient one-pot synthesis of avones by the treatment of 2-hydroxyacetophenones with the corresponding aroyl chloride in wet K 2 CO 3 /acetone (1% w/w water), 8 but the reaction proceeded very slowly because the trihydroxyacetophenone (2) was insoluble in acetone. With water-toluene as the solvent, in the presence of K 2 CO 3 and tetrabutylammonium hydrogen sulfate, 9 the reaction could provide avone 4a in 30% yield and 3-acylated product 4b in 50% yield in one-pot in about two hours. Many efforts to improve the yield of 4a failed, but 4b could be converted into 4a by hydrolysis in 50% yield.10 Aerwards, acylation of 4a with trimethoxybenzoyl chloride (3) and K 2 CO 3 gave 7-Ogalloylavone 5 in 91% yield, which was then reduced to the avan 6 by hydrogenation with palladium on carbon as the catalyst for 3 days in 62% yield. 11When avan 6 was treated with BBr 3 in dichloromethane at À40 C or À78 C, 12 the desired product 1a was generated in only 3% yield (based on HPLC-MS analysis), accompanied with 4-O-methyl gallic acid (7) and avan 8 as the major products, indicating the ester bond of hex-O-methylavan 6 is highly unstable under acidic conditions (Scheme 1).Then, 5-O-methylavan 9, 5-O-acetylavan 10 and 5-O-phenylacetylavan 11 were prepared as substrates to explore if they provided different results (Scheme 2). Similarly, 5-O-acetylavan 10 and 5-O-phenylacetylava...

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Antiviral Flavans from the Leaves of Pithecellobium clypearia

Cited by 61 publications

References 8 publications

Phenolic Compounds from the Flowers of Bombax malabaricum and Their Antioxidant and Antiviral Activities

Phenolic Compounds from the Flowers of Bombax malabaricum and Their Antioxidant and Antiviral Activities

Chemosensitization as a Means to Augment Commercial Antifungal Agents

A concise synthesis of (±)-7-O-galloyltricetiflavan

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