Efficient synthesis of baicalin and its analogs

A Comprehensive Review of Natural Flavonoids with Anti-SARS-CoV-2 Activity

The COVID-19 pandemic caused by SARS-CoV-2 has majorly impacted public health and economies worldwide. Although several effective vaccines and drugs are now used to prevent and treat COVID-19, natural products, especially flavonoids, showed great therapeutic potential early in the pandemic and thus attracted particular attention. Quercetin, baicalein, baicalin, EGCG (epigallocatechin gallate), and luteolin are among the most studied flavonoids in this field. Flavonoids can directly or indirectly exert antiviral activities, such as the inhibition of virus invasion and the replication and inhibition of viral proteases. In addition, flavonoids can modulate the levels of interferon and proinflammatory factors. We have reviewed the previously reported relevant literature researching the pharmacological anti-SARS-CoV-2 activity of flavonoids where structures, classifications, synthetic pathways, and pharmacological effects are summarized. There is no doubt that flavonoids have great potential in the treatment of COVID-19. However, most of the current research is still in the theoretical stage. More studies are recommended to evaluate the efficacy and safety of flavonoids against SARS-CoV-2.

Synthesis and structure of d-glucuronolactone derived carboxamides

5-O-Protected and 1,2-acetonide-protected D-glucurono-6,3-lactone furanosides were converted into novel furano-glucuronamides through treatment with ammonia. Several O3 protections and O5-deprotection routes afford new primary gluconamide derivatives. However, attempted O3-benzylations of O5-protected intermediates led instead to silyl migration (from O5-TDBMS), competitive N-benzylation or reclosure to the lactone are observed as competing processes. This is not seen the using 5-O-PMB protection which the provides the method of choice for obtaining a fully protection-differentiated glucofuranamide. X-ray crystal structures of a fully-protected glucurono-6,3-lactone lactone and a glucuronamide derivatives are reported.

Small Carbohydrate Derivatives as Potent Antibiofilm Agents

Biofilm formation by most pathogenic bacteria is considered as one of the key mechanisms associated with virulence and antibiotic resistance. Biofilm-forming bacteria adhere to the surfaces of biological or implant medical devices and create communities within their self-produced extracellular matrix that are difficult to treat by existing antibiotics. There is an urgent need to synthesize and screen structurally diverse molecules for their antibiofilm activity that can remove or minimize the bacterial biofilm. The development of carbohydrate-based small molecules as antibiofilm agents holds a great promise in addressing the problem of the eradication of biofilm-related infections. Owing to their structural diversity and specificity, the sugar scaffolds are valuable entities for developing antibiofilm agents. In this perspective, we discuss the literature pertaining to carbohydrate-based natural antibiofilm agents and provide an overview of the design, activity, and mode of action of potent synthetic carbohydrate-based molecules.

An Update on Pharmacological Relevance and Chemical Synthesis of Natural Products and Derivatives with Anti SARS-CoV-2 Activity

Natural products recognized traditionally as a vital source of active constituents in pharmacotherapy. The COVID-19 infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is highly transmissible, pathogenic, and considered an ongoing global health emergency. The emergence of COVID-19 globally and the lack of adequate treatment brought attention towards herbal medicines, and scientists across the globe instigated the search for novel drugs from medicinal plants and natural products to tackle this deadly virus. The natural products rich in scaffold diversity and structural complexity are an excellent source for antiviral drug discovery. Recently the investigation of several natural products and their synthetic derivatives resulted in the identification of promising anti SARS-CoV-2 agents. This review article will highlight the pharmacological relevance and chemical synthesis of the recently discovered natural product and their synthetic analogs as SARS-CoV-2 inhibitors. The summarized information will pave the path for the natural product-based drug discovery of safe and potent antiviral agents, particularly against SARS-CoV-2.

Microbial Transformation of Galangin Derivatives and Cytotoxicity Evaluation of Their Metabolites

Galangin (1), 3-O-methylgalangin (2), and galangin flavanone (3), the major bioactive flavonoids isolated from Alpinia officinarum, were biotransformed into one novel and four known metabolites (4–8) by application of the fungal strains Mucor hiemalis and Absidia coerulea as biocatalysts. Their structures were characterized by extensive spectroscopic analyses including one- and two-dimensional nuclear magnetic resonance spectroscopy and mass spectrometry. Compounds 1–7 were evaluated for their cytotoxic activities against cancer cell lines using the MTT assay. The new compound 3-O-methylgalangin-7-O-β-D-glucopyranoside (6) exhibited the most potent cytotoxic activity against MCF-7, A375P, B16F10, B16F1, and A549 cancer cell lines with the IC50 values at 3.55–6.23 μM.

Efficacy and sustainability of natural products in COVID-19 treatment development: opportunities and challenges in using agro-industrial waste from Citrus and apple

Natural products have been used in the treatment of illnesses throughout the history of humankind. Exploitation of bioactive compounds from natural sources can aid in the discovery of new drugs, provide the scaffold of new medicines. In the face of challenging diseases, such as the COVID-19 pandemic, for which there was no effective treatment, nature could offer insights as to novel therapeutic options for control measures. However, the environmental impact and supply chain of bioactive production must be carefully evaluated to ensure the detrimental effects will not outweigh the potential benefits gained. History has already proven that highly bioactive compounds can be rare and not suitable for medicinal exploitation; therefore, the sustainability must be accessed before expensive, time-demanding, and large trials can be initialized. A sustainable option to readily produce a phytotherapy with minimal environmental stress is the use of agro-industry wastes, a by-product produced in high quantities. In this review we evaluate the sustainability issues associated with the production of phytotherapy as a readily available tool for pandemic control.

Anti-tumor effect of synthetic baicalin-rare earth metal complex drugs on SMMC-7721 cells

Baicalin (BC)-rare earth metal complexes [BMCs (BC-Ce, BC-La, and BC-Y)] were synthesized by a complexation coordination method. A mouse tumor model with SMMC-7721 cells was used to examine BMCs for their anti-tumor activities in vivo. The results show that the three new BMCs, Na₃Ce (C₂₁H₁₆O₁₁)₃·10H₂O, Na₂La (C₂₁H₁₆O₁₁)₂·8H₂O, and Na₂Y (C₂₁H₁₆O₁₁)₂·6H₂O significantly inhibited SMMC-7721 cell proliferation, since the BMCs may induce the tumor apoptosis in a dose-dependent manner through decreasing cell membrane fluidity and mitochondrial membrane potential depolarization, blocking of the cell cycle at the G₂/M phase, and increasing the expression of Bax and reducing the expression of Bcl-2. The effectiveness order of these three BCMs was as follows: BC-Ce > BC-La > BC-Y > BC. It is concluded that BC-Ce, BC-La, and BC-Y possess potent anti-tumor effects and may be a novel group of anti-tumor drugs. The novel baicalin-rare earth metal complexes (BMC) were synthesized, the anti-tumor effects of the BMC on SMMC-7721 cell analyzed comprehensively.

Concise synthesis and antidiabetic activity of natural flavonoid glycosides, oroxins C and D, isolated from the seeds of Oroxylum indium

The first concise synthesis of natural flavonoid glycosides, oroxins C (1) and D (2), which were isolated from the seeds of Oroxylum indicum, was efficiently achieved by a convergent strategy. The synthesized natural products 1 and 2 were evaluated for their inhibitory activities against α-glucosidase, α-amylase, and lipase. Compound 1 showed strong α-amylase and lipase inhibition, with IC50 values of 210 and 190 μM, respectively, but exhibited no inhibitory activity against α-glucosidase. Compound 2 showed strong inhibition against α-glucosidase and lipase, with the respective IC50 values of 180 and 80 μM.

Highly efficient synthesis of flavonol 5-O-glycosides with glycosyl ortho-alkynylbenzoates as donors

A highly efficient approach to construct the challenging flavonol 5-O-glycosidic linkages is developed, providing a general synthetic route to flavonol 5-O-glycosides.