Short synthesis of phenylpropanoid glycosides calceolarioside-B and eutigoside-A

Synthesis and pharmacological evaluation of nature-inspired phenacyl glycosides

Phenylethanoid glycosides are a well-studied class of bioactive compounds found throughout the plant kingdom. In contrast, research on the synthesis and pharmacological activity of phenacyl glycosides, a specific subgroup of phenylethanoid glycosides with a ketone functionality at the alpha position of the phenol ring, has been limited. In this study, we report the synthesis, cytotoxic, antiviral, and anti-inflammatory evaluation of a series of 18 4'-hydroxyphenacyl glycosides. These compounds consist of six different sugar residues (β-d-glucose, β-d-galactose, α-l-arabinose, β-d-xylose, α-l-rhamnose, and β-d-glucuronic acid) and display three distinct methoxylation patterns at the phenacyl ring, similar to the substitution motifs of anthocyanins. We obtained the target phenacyl glycosides in high yield and stereoselectivity through the coupling of benzoyl-protected trichloroacetimidate glycosyl donors and corresponding acetophenones. Our work represents the first total synthesis of the natural products 4'-hydroxyphenacyl-β-d-glucopyranoside (1) and 4'-hydroxy-3'-methoxyphenacyl-β-d-glucopyranoside (2). None of the phenacyl glycosides showed cytotoxicity against the tested cell lines. Notably, several of the synthesized compounds exhibited antiviral activity, with natural product 2 being the most active against herpes simplex virus type 1, while phenacyl arabinoside 9 and natural product 2 were the most active against human coronavirus OC43. Natural product 2 significantly inhibited the production of interleukin-6 in lipopolysaccharide-stimulated microglia cells. Overall, our findings highlight the importance of the sugar residue and phenacyl ring substitution pattern in modulating the antiviral activity of phenacyl glycosides. Natural product 2 and phenacyl arabinoside 9 emerge as promising leads for the development of antiviral agents.

Synthesis of phenylethanoid glycosides from acrylic esters of glucose and aryldiazonium salts via palladium-catalyzed cross-coupling reactions and evaluation of their anti-Alzheimer activity

Cinnamic acid-containing sugar compounds such as phenylethanoid glycosides are widely present in nature and display various biological activities. In this work, the synthesis of trans-cinnamic acid containing phenylethanoid glycosides was achieved via palladium-catalyzed cross-coupling reactions between glycosyl acrylic esters and aryldiazonium salts. A wide range of functionalized aryldiazonium salts were successfully coupled with 6-O- and 4-O-acrylic esters of glucose under optimized conditions. The reactions proceeded at room temperature in the absence of additives and base. The desired products were obtained in good to excellent yields. Selected compounds from the library were screened for anti-Alzheimer activity, while compound 16 displayed significant inhibitory activities against butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) enzymes.

A review on the structure and pharmacological activity of phenylethanoid glycosides

Phenylethanoid glycosides (PhGs) are compounds made of phenylethyl alcohol, caffeic acid and glycosyl moieties. The first published references about phenylethanoid glycosides concerned the isolation of echinacoside from Echinaceu ungustifolia (Asteraceae) in 1950 and verbascoside from Verbascum sinuatum (Scrophulariaceae) in 1963. Over the past 60 years, many compounds with these structural characteristics have been isolated from natural sources, and most of these compounds possess significant bioactivities, including antibacterial, antitumor, antiviral, anti-inflammatory, neuro-protective, antioxidant, hepatoprotective, and immunomodulatory activities, among others. In this review, we will summarize the phenylethanoid glycosides described in recent papers and list all the compounds that have been isolated over the past few decades. We will also attempt to present and assess recent studies about the separation, extraction, determination, and pharmacological activity of the excellent natural components, phenylethanoid glycosides.

A review on traditional uses, phytochemistry and pharmacological activities of the genus Ballota

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Ballota L. (Lamiaceae) comprises 33 to 35 species distributed mainly in temperate and subtropical regions of the world. Some species have been used in folk medicine as antiemetic, antispasmodic, sedative agents, vermifuge, antihemorrhoid and also in treatment of cough, etc. AIM OF THIS REVIEW: This review article aims to provide organized information on the available traditional uses, phytochemical and pharmacological studies of the genus Ballota, and to obtain new insights for further researches.

MATERIALS AND METHODS

Electronic databases, including Web of Science, Science Direct, Google Scholar, Scopus, PubMed, and Springer Link were used as information sources. General web searches were carried out using Google and Yahoo search engines by applying related search terms. Additional information was derived from books and journals in English, Latin and Persian, and also Ph.D. theses and M.Sc. dissertations.

RESULTS

Terpenoids (particularly furanolabdane diterpenoids) and flavonoids were the main phytochemical classes identified in the extracts of Ballota species. Furanolabdane diterpenoids, e.g. ballonigrin, dehydrohispanolone, and hispanolone were reported in many species of Ballota. β-Caryophyllene, caryophyllene oxide, and germacrene D were found as the most common major compounds isolated from the essential oils of the genus Ballota. Sixty-four pharmacological studies conducted on cell lines, microorganisms, and animals were included in this review. Some species of Ballota exhibited various pharmacological activities, including promising antidepressant, anxiolytic, sedative-hypnotic, and antitussive activities in animal models. The pharmacological activities can be attributed to bioactive phytochemicals.

CONCLUSION

The genus Ballota is a valuable source of bioactive compounds with therapeutic potential in different diseases. Some pharmacological studies showed incomplete methodologies and ambiguous findings. Thus, the research designs of pharmacological studies based on traditional uses of Ballota species are strongly needed in cell lines and animal models. More in vitro and in vivo animal studies are required to confirm the safety, clarification of the effective doses, bioactive compounds, and the mechanisms of actions before future clinical studies.

Total synthesis of phenylpropanoid glycoside osmanthuside-B6 facilitated by double isomerisation of glucose–rhamnose orthoesters

Osmanthuside-B₆ was synthesized in 22% overall yield. The synthesis involved a newly discovered glucose–rhamnose orthoester double isomerization process.