Recent advances on natural depsidones: sources, biosynthesis, structure-activity relationship, and bioactivities.

Depsidones are a class of polyphenolic polyketides that have been proposed to be biosynthesized from oxidative coupling of esters of two polyketidic benzoic acid derivatives. They are principally encountered in fungi and lichens. In addition to their diversified structural features, they revealed varied bioactivities such as antimicrobial, antimalarial, cytotoxic, anti-inflammatory, anti-Helicobacter pylori, antimycobacterial, antihypertensive, anti-diarrheal, antidiabetic, phytotoxic, anti-HIV, anti-osteoclastogenic, and butyrylcholinesterase, tyrosinase, hyaluronidase, and acetylcholinesterase inhibition. The current work was targeted to provide an overview on the naturally reported depsidones from various sources in the period from 2018 to the end of 2022 including their structures, biosynthesis, sources, and bioactivities, as well as the reported structure-activity relationship and semisynthetic derivatives. A total of 172 metabolites with 87 references were reviewed. The reported findings unambiguously demonstrated that these derivatives could be promising leads for therapeutic agents. However, further in-vivo evaluation of their potential biological properties and mechanistic investigations are needed.

Mangostanaxanthone VIIII, a new xanthone from Garcinia mangostana pericarps, α-amylase inhibitory activity, and molecular docking studies

ABSTRACT A new xanthone: mangostanaxanthone VIIII [1,3,5,6,7-pentahydroxy-2-(3-methylbut-2-enyl)-8-(3-hydroxy-3-methylbut-1-enyl) xanthone] (5) and four known xanthones: mangostanaxanthones I (1) and II (2), γ-mangostin (3), and mangostanaxanthone VII (4) were separated and characterized from the acetone fraction of Garcinia mangostana L., Clusiaceae (mangosteen) pericarps. Their structures were established based on various spectroscopic analyses in addition to HRMS and comparison with the literature. The α-amylase inhibitory potential of the isolated metabolites was evaluated. Compounds 1, 2, and 5 had the highest activity with % inhibition 72.5, 86.5, and 81.8, respectively compared to acarbose (97.1%, reference α-amylase inhibitor). The molecular docking study of the tested metabolites was estimated to shade up the rational explanation of the α-amylase inhibitory activity results. Moreover, the pharmacokinetic parameters were assessed using Swiss ADME. It is noteworthy that 1, 2, and 5 had similar binding poses as the X-ray crystal structure of acarbose, whereas the other metabolites possessed different binding mode that decreased their inhibitory capacity. Thus, these data reinforced the health benefit of mangosteen as an alternative medicine to help lowering the postprandial glucose absorption. Therefore, it could have a good potential for the treatment of diabetes.

Lipoxygenase inhibitors flavonoids from Cyperus rotundus aerial parts

ABSTRACT Cyperus rotundus L. (Suada, Sueda, family: Cyperaceae) is vastly spread in several world's subtropical and tropical regions. It had variable traditional uses and bioactivities. A new flavonol derivative: cyperaflavoside (myricetin 3,3',5'-trimethyl ether 7-O-β-D-glucopyranoside) and five flavonoids: vitexin, orientin, cinaroside, quercetin 3-O-β-D-glucopyranoside, and myrcetin 3-O-β-D-glucopyranoside were separated from the methanolic extract of C. rotundus aerial parts. Their structures were verified based on UV, IR, NMR (1D and 2D), HRESIMS, and comparison with literature. All metabolites were assessed for their 5-lipoxygenase inhibitory potential. All compounds possessed 5-lipoxygenase inhibitory potentials with IC50s 5.1, 4.5, 5.9, 4.0, 3.7, and 2.3 µM, respectively, in comparison to indomethacin (IC50 0.98 µM). These results supported the traditional uses of C. rotundus in treating inflammation and its related symptoms.

Plectraterpene, a new ursane-type triterpene ester and other steroids from the aerial parts of Plectranthus montanus

ABSTRACT A new ursane-type triterpene ester, plectraterpene [3β-(decanoyloxy)-19-hydroxy-urs-12-ene] and four known steroidal compounds have been isolated from the aerial parts of Plectranthus montanus Benth. (syn. Plectranthus cylindraceus Hochst. ex Benth.), Lamiaceae. The known compounds were stigmasterol, sitosteryl ferulate, cholest-5-en-3-O-β-D-glucopyranoside and stigmasterol-3-O-β-D-glucopyranoside. Compounds plectraterpene, sitosteryl ferulate and stigmasterol-3-O-β-D-glucopyranoside are reported for the first time from this plant whereas compound cholest-5-en-3-O-β-D-glucopyranoside first time from the genus. The structures of these compounds were determined through spectral analysis, including extensive 2D NMR data as well as chemical methods and comparison with literature.

Cucumin S, a new phenylethyl chromone from Cucumis melo var. reticulatus seeds

ABSTRACTA new phenylethyl chromenone, cucumin S [(R)-5,7-dihydroxy-2-[1-hydroxy-2-(4-hydroxy-3-methoxyphenyl)ethyl]chromone] (1), along with five known compounds: 5,7-dihydroxy-2-[2-(4-hydroxyphenyl)ethyl]chromone (2), 5,7-dihydroxy-2-[2-(3,4-dihydroxyphenyl)ethyl]chromone (3), luteolin (4), quercetin (5), and 7-glucosyloxy-5-hydroxy-2-[2-(4-hydroxyphenyl)ethyl]chromone (6) were isolated from the EtOAc fraction of Cucumis melo var. reticulatus Ser., Cucurbitaceae, seeds. Their structures were determined by spectroscopic means (1D and 2D NMR), as well as HRESIMS, optical rotation measurement, and comparison with literature data. The isolated compounds 1–6 were assessed for their antioxidant activity using DPPH assay. Compounds 3, 4, and 5 showed potent activities compared to propyl gallate at concentration 100 µM.