Eucalyptusdimers A–C, Dimeric Phloroglucinol–Phellandrene Meroterpenoids from Eucalyptus robusta

Abstract

Eucalyptusdimers A-C, three dimeric phellandrene-derived meroterpenoids featuring an unprecedented, fused skeleton between two phellandrene and two acylphloroglucinol subunits, along with one biogenetically related intermediate, (±)-eucalyprobusone A, were isolated from the fruits of Eucalyptus robusta. Their structures and absolute configurations were elucidated using spectroscopic data, X-ray crystallography, and electronic circular dichroism analysis. The isolated meroterpenoids were evaluated for their anti-inflammatory, acetylcholinesterase inhibitory, and protein tyrosine phosphatase 1B inhibitory effects.

Acylphloroglucinols with acetylcholinesterase inhibitory effects from the fruits of Eucalyptus robusta

“…(Table 4). Taking their structural characteristics and AChE inhibitory data into consideration, the observable structure-activity relationships can be summarized as follows (i) both FPMs featuring with a dihydropyran ring and acylphloroglucinol monomer were inactive; (ii) acylphloroglucinol dimers that be connected via an isopentyl moiety showed stronger AChE inhibitory effects than Rhodomyrtus tomentosa [35], the current findings indicated that FPM and acylphloroglucinol heterodimers [10] connected only by an isopentyl unit are more likely to be AChE inhibitors.…”

“…Plants of Eucalyptus genus (Myrtaceae) are a prolific resource of phloroglucinol derivatives, especially formylated phloroglucinol meroterpenoids (FPMs) [1][2][3][4]. These Eucalyptus secondary metabolites not only possess multifarious bioactive properties, including protein tyrosine phosphatase 1B inhibitory [2], immunosuppressive [3], antimicrobial [4,5], antiviral [6], anticancer [7][8][9], AChE inhibitory [10], and anti-leishmanial [11] effects, but also have attracted significant attention from the synthetic organic chemistry community [12][13][14][15][16][17][18]. Eucalyptus robusta, a tall arbor indigenous to Australia, is widely cultivated in south China.…”

“…The PE (petroleum ether)-EtOAc (ethyl acetate) extract of E. robusta fruits displayed an AChE inhibitory rate of 68% at the concentration of 500 μg/mL, which prompted further phytochemical investigation with the aim at clarifying its bioactive constituents. As a result, five new FPMs, eucalyprobusals A-F (1-6), one monomeric acylphloroglucinol, eucalyprobusone B (7), and four acylphloroglucinol dimers, eucalyprobusones B-F (8)(9)(10)(11) were isolated and structurally characterized ( Fig. 1).…”

Polymethylated Phloroglucinol Meroterpenoids from Rhodomyrtus tomentosa and Their Antibacterial and Acetylcholinesterase Inhibitory Effects

“…These natural products have also attracted considerable interests from our research group. [7][8][9] As part of our continuing efforts to search for structurally intriguing and bioactive molecules from Myrtaceae family, three new polymethylated phloroglucinol meroterpenoids (PPMs), named rhotomentodiones CÀ E (Figure 1), were obtained from the twigs and leaves of Rhodomyrtus tomentosa. All these isolates were evaluated for their antibacterial and AChE inhibitory activities.…”

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“…Further unusual natural products whose structures have been confirmed by X-ray analyses include cleistoperlones A 7 and C 8, from Cleistocalyx operculatus, 7 and eucalyptusdimer A 9, from Eucalyptus robusta. 8 Cleistoperlone A 7 is formed from two cinnamylphloroglucinol units and cleistoperlone C 8, from a cinnamylphloroglucinol unit with α-pinene. Three homologous cytochrome P450 enzymes from three indole alkaloid-producing plants have been discovered and shown to allow entry to two distinct classes of alkaloids, the sarpagans (e.g.…”