Hyperacmosins H-J, three new polycyclic polyprenylated acylphloroglucinol derivatives from Hypericum acmosepalum

Hypericum Genus as a Natural Source for Biologically Active Compounds

Hypericum L. genus plants are distributed worldwide, with numerous species identified throughout all continents, except Antarctica. These plant species are currently used in various systems of traditional medicine to treat mild depression, wounds and burns, diarrhea, pain, fevers, and their secondary metabolites previously shown, and the in vitro and/or in vivo cytotoxic, antimicrobial, anti-inflammatory, antioxidant, antihyperglycemic, and hepatoprotective activities, as well as the acetylcholinesterase and monoamine oxidase inhibitory activities. We conducted a systematic bibliographic search according to the Cochrane Collaboration guidelines to answer the question: "What is known about plants of Hypericum genus as a source of natural products with potential clinical biological activity?" We documented 414 different natural products with confirmed in vitro/in vivo biological activities, and 58 different Hypericum plant species as sources for these natural products. Phloroglucinols, acylphloroglucinols, xanthones, and benzophenones were the main chemical classes identified. The selective cytotoxicity against tumor cells, cell protection, anti-inflammatory, antimicrobial, antidepressant, anti-Alzheimer's, and adipogenesis-inhibition biological activities are described. Acylphloroglucinols were the most frequent compounds with anticancer and cell-protection mechanisms. To date, no work has been published with a full descriptive list directly relating secondary metabolites to their species of origin, plant parts used, extraction methodologies, mechanisms of action, and biological activities.

Hyperacmosin R, a New Decarbonyl Prenylphloroglucinol with Unusual Spiroketal Subunit from Hypericum acmosepalum

Two previously undescribed polycyclic polyprenylated acylphloroglucinols, hyperacmosins R-S (1–2), were obtained from the aerial parts of Hypericum acmosepalum. Their structures were elucidated by extensive spectroscopic analysis and electronic circular dichroism calculation (ECD). Compound 1 featured an unprecedented 5,8-spiroketal subunit as well as the loss of C-2′ carbonyl in the phloroglucinol ring. In addition, compounds 1 and 4 showed weak hepatoprotective activity against paracetamol-induced HepG2 cell damage at 10 μm. The plausible biosynthetic pathway of 1 was proposed via a retro-Clasisen reaction and decarboxylation.

Four new polycyclic polyprenylated acylphloroglucinols from Hypericum wilsonii and their glucose uptake bioactivities

Wilsonglucinols H-K (1-4), four new polycyclic polyprenylated acylphloroglucinols (PPAPs), and eight known compounds (5-12) were isolated and identified from the aerial parts of Hypericum wilsonii. Their planner structures were confirmed via extensive NMR and HRESIMS data analysis. The absolute configurations of the new compounds were mainly determined by NMR calculation and electronic circular dichroism (ECD) calculation. Compounds 1, 6, 8, and 10 showed glucose uptake activities at 30 μg/mL, in which compound 6 showed the strongest effect and increased the glucose uptake by 2.73 folds.

Hyperacmosins K-M, three new polycyclic polyprenylated acylphloroglucinols from Hypericum acmosepalum

Hyperacmosins K-M (1-3), three new polycyclic polyprenylated acylphloroglucinol (PPAPs) derivatives, were isolated from the air-dried aerial parts of Hypericum asmosepalum. Compounds 1 and 2 both possessed a rare 5,5-spiroketal subunit with the loss of C-2' carbonyl in the phloroglucinal ring, while compound 3 featured an unusual 1,2-seco-bicyclo[3.3.1] PPAP skeleton. Their structures were confirmed by NMR, HRESIMS, and CD spectra. The plausible biogenetic pathways of 1-3 were proposed, which gave an insight for future biomimetic synthesis of the novel compounds.

Acmoxanthones A-E, New Lavandulated Xanthones from Hypericum acmosepalum N. Robson

Acmoxanthones A-E (1-5), five new lavandulylated xanthones, were isolated from the aerial parts of Hypericum acmosepalum, together with four known xanthones. Their structures with absolute configurations were elucidated on the basis of analysis of MS, NMR and chiroptical properties. A bioassay against high glucose-induced damage on human umbilical vein endothelial cells (HUVECs) showed ananixanthone (6) and osajaxanthone (7) had potential antioxidative damage activity with EC₅₀ values of 10.5 μg/mL and 7.6 μg/mL, respectively, while 3-hydroxy-2,4-dimethoxyxanthone (8) exhibited cytotoxic effect on the damaged cells with IC₅₀ values of 7.1 μg/mL.