Labdane‐type diterpenoids from Leonurus heterophyllus and their cholinesterase inhibitory activity

Abstract

In the course of screening plants used in natural medicines as memory enhancers, a 70% ethanol extract of the aerial parts of Leonurus heterophyllus showed significant AChE inhibitory activity. Bioassay-guided fractionation and repeated column chromatography led to the isolation of a new labdane-type diterpenoids (1), named leoheteronin F, and six known compounds (2-7). The chemical structures of isolated compounds were elucidated based on extensive 1D and 2D NMR spectroscopic data. The isolates 1-7 were investigated in vitro for their anticholinesterase activity using mouse cortex AChE enzyme. Leoheteronin A (5) and leopersin G (7), which possess a 15,16-epoxy group at the side chain, were found to be potent in the inhibition of AChE.

Cholinesterase-inhibitory diterpenoids and chemical constituents from aerial parts of Caryopteris mongolica

“…The diethyl ether fraction was chromatographed on a Diaion HP-20 column and HPLC to obtain 8, 14, and 15. The known compounds (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) were identified based on spectroscopic data as hypolaetin 7-O-b-D-glucopyranoside (6) [18,19], luteolin (7) [20], acacetin (8) [21], hypolaetin (9) [22], luteolin 7-O-[6 00 -O-(trans-caffeoyl)]-b-D-glucopyranoside (10) [20,23] [20], luteolin 7-O-b-D-glucuronopyranoside (12) [24], luteolin 7-O-rutinoside (13) [25,26], 12-O-demethylcryptojaponol (14) [27], 6a-hydroxydemethylcryptojaponol (15) [28], and incanide B (20) [29]. Four phenylethanoid glycosides, acteoside (16), isoacteoside (17), martynoside (18), and stachysoside (19) were identified by comparison with compounds isolated previously from Leucosceptrum japonicum by our group [30] (Fig.…”

“…In assay methods, the AChE from electric eel, which is not a mammal, has often been used for screening AChE inhibitors because it is similar to the vertebrate nerve and muscle AChE [17]. Thus, in order to estimate the cholinesterase-inhibitory activities of the components isolated (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), including diterpenoids and diterpenoid glycosides, inhibition activities against AChE from human erythrocytes, AChE from electric eel, and BChE from horse serum were evaluated.…”

“…In this study, a diterpenoid diglucoside (1) and four flavone glycosides (2)(3)(4)(5) together with 15 known compounds (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), including two abietane-type diterpenoids (14,15) were obtained as the constituents of aerial parts of C. mongolica collected in Töv Province, Mongolia (Fig. 1).…”

“…1). In the last decade, various groups have reported Lamiaceae diterpenoids which have anticholinesterase activities, such as clerodane-type diterpenoids and tetracyclic diterpenoids from Ballota limbata [5], cis-clerodane-type tricyclic diterpenoids from Otostegia limbata [6], ent-kaurane diterpenoids from Isodon wightii and Sideritis arguta and congesta [7][8][9], cryptotanshinone from Salvia miltiorrhiza [10], kabdane-type diterpenoids from Leonurus heterophyllus [11], taxodion and ferruginol from Salvia stamines [12], and sclareol from Salvia chrysophylla [13]. These were mentioned as potent acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors because both AChE and BChE are targets of candidate phytochemicals for the treatment of neurodegenerative disorders such as Alzheimer's disease (AD) because of the cholinergic hypothesis [14].…”

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A diterpenoid diglucoside (12,11,and 15 known compounds were isolated from aerial parts of the Mongolian medicinal plant Caryopteris mongolica. The cholinesterase-inhibitory activities of the constituents were estimated.

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