Botany, phytochemistry, pharmacology, and potential application of Polygonum cuspidatum Sieb.et Zucc.: A review

The screening and testing of extracts against a variety of pharmacological targets in order to benefit from the immense natural chemical diversity is a concern in many laboratories worldwide. And several successes have been recorded in finding new actives in natural products, some of which have become new drugs or new sources of inspiration for drugs. But in view of the vast amount of research on the subject, it is surprising that not more drug candidates were found. In our view, it is fundamental to reflect upon the approaches of such drug discovery programs and the technical processes that are used, along with their inherent difficulties and biases. Based on an extensive survey of recent publications, we discuss the origin and the variety of natural chemical diversity as well as the strategies to having the potential to embrace this diversity. It seemed to us that some of the difficulties of the area could be related with the technical approaches that are used, so the present review begins with synthetizing some of the more used discovery strategies, exemplifying some key points, in order to address some of their limitations. It appears that one of the challenges of natural product-based drug discovery programs should be an easier access to renewable sources of plant-derived products. Maximizing the use of the data together with the exploration of chemical diversity while working on reasonable supply of natural product-based entities could be a way to answer this challenge. We suggested alternative ways to access and explore part of this chemical diversity with in vitro cultures. We also reinforced how important it was organizing and making available this worldwide knowledge in an "inventory" of natural products and their sources. And finally, we focused on strategies based on synthetic biology and syntheses that allow reaching industrial scale supply. Approaches based on the opportunities lying in untapped natural plant chemical diversity are also considered.

Unraveling Plant Natural Chemical Diversity for Drug Discovery Purposes

Three indole alkaloid glycosides, strobilanthosides A-C (1-3), two known indole alkaloid glucosides (4 and 5), and five phenylethanoid glycosides (8-10) were isolated from the aerial parts of Strobilanthes cusia. The structures of the new compounds were elucidated by spectrometric analysis, and the absolute configurations of 1 and 2 were established by ECD spectrocsopy. N'-β-d-Glucopyranosylindirubin (5) showed weak antibacterial activity (MIC 62.5-125 μM) against Staphylococcus aureus.

Indole Alkaloid Glycosides From the Aerial Parts of Strobilanthes Cusia

Rapid profiling and pharmacokinetic studies of major compounds in crude extract from Polygonum multiflorum by UHPLC-Q-TOF-MS and UPLC-MS/MS.

Ceratodon purpureus is a cosmopolitan moss that survives some of the harshest places on Earth: from frozen Antarctica to hot South Australian deserts. In a study on the survival mechanisms of the species, nine compounds were isolated from Australian and Antarctic C. purpureus. This included five biflavonoids, with complete structural elucidation of 1 and 2 reported here for the first time, as well as an additional four known phenolic compounds. Dispersion-corrected DFT calculations suggested a rotational barrier, leading to atropisomerism, resulting in the presence of diastereomers for compound 2. All isolates absorbed strongly in the ultraviolet (UV) spectrum, e.g., biflavone 1 (UV-A, 315–400 nm), which displayed the strongest radical-scavenging activity, 13% more efficient than the standard rutin; p-coumaric acid and trans-ferulic acid showed the highest UV-B (280–315 nm) absorption. The more complex and abundant 1 and 2 presumably have dual roles as both UV-screening and antioxidant compounds. They are...

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Antarctic Moss Biflavonoids Show High Antioxidant and Ultraviolet-Screening Activity

Polyflavanostilbene A, a new flavanol-fused stilbene glycoside from Polygonum cuspidatum.

In recent years, certain "new" naturally occurring compounds (1-28) with 3,5-dioxygenated aromatic rings have been reported. A comparison of the NMR data of these compounds with the data of four model compounds (A-D) indicated that the structures of these "new" compounds were erroneous. The reason for the incorrect elucidation of the structures of 1-28 was attributed to "deceptively simple" (1)H NMR spectra, which displayed two broad singlets with integrations of 1:2 for H-2 and H-5, H-6, respectively. To expose the misleading results from the spectra, serial (1)H NMR experiments on compounds A-D were performed using various deuterated solvents and temperatures. The results revealed separated proton signals for the ABX system in certain deuterated solvents. Additionally, the characteristic differences between 3,4- and 3,5-dioxygenated aromatic rings in their (13)C NMR spectra are summarized based on our experiment and data reported. This approach is useful for analyzing the patterns of dioxygenated aromatic rings in natural products, especially when "deceptively simple" (1)H NMR spectra are displayed.

NMR spectroscopic method for the assignment of 3,5-dioxygenated aromatic rings in natural products.

Neuroprotective naphthalene and flavan derivatives from Polygonum cuspidatum.

A photocatalytic protocol for the synthesis of β-amino acid ester and β-amino ketone derivatives is developed by using simple and easy-to-synthesize oxime oxalate and oxime phenylglyoxylate as difunctionalization reagents. These...

Fu Liu

Papers

Polyflavanostilbene A, a new flavanol-fused stilbene glycoside from Polygonum cuspidatum.

NMR spectroscopic method for the assignment of 3,5-dioxygenated aromatic rings in natural products.

Neuroprotective naphthalene and flavan derivatives from Polygonum cuspidatum.

Efficient Access to β-Amino Acid Ester/β-Amino Ketone Derivatives via Photocatalytic Radical Alkoxycabonylimidation/ Carbonylimidation of Alkenes

Acyl glycosides lignans, coumarins, and terpenes from the stems of Erycibe obtusifolia.