Oligoepicatechins from the Leaves of Machilus konishii

Epicatechin ( 3 ) and five oligomers ( 2 , 4 , 5 , 10 , 11 ) together with five other type compounds were isolated and characterized from n‐BuOH and EtOAc soluble fractions of the ethanol extract of the leaves of Machilus konishii Hayata. Their structures were elucidated by means of MS and NMR spectroscopic analyses. Dehydrodiepicatechin A ( 11 ) is the first occurrence as a natural product although it has been prepared from epicatechin. The stereochemistry of 11 is elucidated for the first time on the basis of 1D NOESY and chemical model analyses. Tiliroside ( 7 ) and kaempferol 3‐O‐α‐L‐(2″,4″‐di‐E‐p‐coumaroyl)‐rhamnopyranoside ( 8 ) showed moderate inhibitory activity against α‐glucosidase.     

Flavonol Glycosides with α‐Glucosidase Inhibitory Activities and New Flavone C‐Diosides from the Leaves of Machilus konishii

Seventeen flavonoids, five of which are flavone C‐diosides, 1 – 5 , were isolated from the BuOH‐ and AcOEt‐soluble fractions of the leaf extract of Machilus konishii. Among 1 – 5 , apigenin 6‐C‐β‐D ‐xylopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 2 ), apigenin 8‐C‐α‐L ‐arabinopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 4 ), and apigenin 8‐C‐β‐D ‐xylopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 5 ) are new. Both 4 and 5 are present as rotamer pairs. The structures of the new compounds were elucidated on the basis of NMR‐spectroscopic analyses and MS data. In addition, the ¹H‐ and ¹³C‐NMR data of apigenin 6‐C‐α‐L ‐arabinopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 3 ) were assigned for the first time. The isolated compounds were assayed against α‐glucosidase (type IV from Bacillus stearothermophilus). Kaempferol 3‐O‐(2‐β‐D ‐apiofuranosyl)‐α‐L ‐rhamnopyranoside ( 12 ) was found to possess the best inhibitory activity with an IC₅₀ value of 29.3 μM .     

Three New Benzophenone Glucosides from the Leaves of Planchonella obovata

Chemical investigation of the EtOH extract of the leaves of Planchonella obovata resulted in the isolation of four benzophenone glucosides, 1 – 4 , of which three, 2 – 4 , are new chemical entities together with five known flavonol glycosides. Their structures were elucidated by spectroscopic analysis. Among the isolated compounds, iriflophenone 2‐O‐(2,6‐di‐O‐galloyl)‐β‐D ‐glucopyranoside ( 4 ) showed some activity (91.4 and 15.0% inhibition at 100 and 10 μg/ml, resp.) against the α‐glucosidase of Bacillus stearothermophilus.     

天然黄酮苷的合成研究进展

黄酮苷类化合物广泛存在于自然界,具有显著的生物活性,是一类重要的天然有机化合物。本文从苷元的合成方法和保护策略以及糖苷缩合反应的方法两方面简要综述了天然黄酮苷的合成研究进展。     

Synthesis and Evaluation of Four Hederagenin Glycosides as α‐Glucosidase Inhibitor

The four hederagenin glycosides 1 – 4 were efficiently synthesized through one‐pot sequential glycosylations with glycose 1‐(trichloroacetimidate)s as donors, resulting in a significantly simplified synthetic procedure without isolation of glycosylation intermediates. The activity of the synthetic hederagenin glycosides 1 – 4 against α‐glucosidase type IV was evaluated; hederagenin glycoside 4 containing an α‐L ‐rhamnopyranosyl unit showed the best activity with an IC₅₀ value of 47.9 μM .     

Flavone Glycosides from Strobilanthes Formosanus

Two new flavone glycosides, 3′‐hydroxy‐5,7‐dimethoxyflavone 4′‐O‐β‐D‐apiofuranoside ( 1 ), and 5,7‐dimethoxyflavone 4′‐O‐[β‐D‐apiofuranosyl(1→5)‐ β‐D‐glucopyranoside] ( 2 ) along with four known compounds, 4′‐hydroxy‐5,7‐dimethoxyflavone ( 3 ), 2,6‐dimethoxy‐1,4‐benzoquinone ( 4 ), lupeol ( 5 ) and betulin ( 6 ) were isolated from the stem and roots of Strobilanthes formosanus. Their structures were elucidated on the basis of their spectroscopic evidence.     

Sesquiterpenoids and Their Glycosides from Gynura procumbens

Chemical investigation of the MeOH extract of the leaves of Gynura procumbens (Lour .) Merr . afforded one new sesquiterpenoid, muurol‐4‐ene‐1β,3β,10β‐triol ( 1 ), and two sesquiterpene glycosides, muurol‐4‐ene‐1β,3β,10β‐triol 3‐O‐β‐D ‐glucopyranoside ( 2 ) and muurol‐4‐ene‐1β,3β,15‐triol 3‐O‐β‐D ‐glucopyranoside ( 3 ), together with three known sesquiterpenoids. Their structures were elucidated on the basis of spectroscopic analyses and chemical methods.     

Xanthone O‐Glycosides from the Roots of Pteris Multifida

Two new xanthone glycosides and six known compounds were isolated from the roots of Pteris multifida. Based on spectroscopic and chemical methods, the structures of the new compounds were elucidated as 1‐hydroxy‐4,7‐dimethoxy‐8‐(3‐methyl‐2‐butenyl)‐6‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐[β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐glucopyranosylxanthone ( 1 ), and 1,3‐dihydroxy‐7‐methoxy‐8‐(3‐methyl‐2‐butenyl)‐6‐O‐α‐L‐rhamnopyranosyl‐(1 →2)‐[β‐D‐glucopyranosyl‐(1→3)]‐β‐D‐glucopyranosylxanthone ( 2 ), respectively.     

Chemical Constituents from the Leaves of Litsea Acutivena

Continuous investigation of the CHCl₃‐soluble and n‐hexane fractions of the leaves of Litsea acutivena Hayata (Lauraceae) led to the isolation of one new butanolide, acutilactone ( 1 ), one new lactone, 4‐nonacosyl‐dihydrofuran‐2‐one ( 2 ), together with 15 known compounds. The known compounds included one butanolide, one norisoprenoid, one quinone, two steroids, one triterpenoid, one coumarin, two fatty acids, one amide, and five other compounds. The structures of these compounds were determined by means of spectral analyses.     

Flavonoid Composition in the Leaves of Twelve Litsea and Neolitsea Plants

This study was aimed to study the chemodiversity of flavonoids in the Formosan Litsea and Neolitsea plants. Applications of LC‐SPE‐NMR and LC/MS hyphenated techniques in analyzing polar constituents from the leaves of L. acuminata, L. hypophaea, N. acuminatissima, and N. konishii led to the identification of 13 known flavonoids and one new flavonol dioside, quercetin 3‐O‐(2‐O‐β‐D ‐apiofuranosyl)‐α‐L ‐rhamnopyranoside. The quantity and variety of flavonoid composition in the leaves of 12 Litsea and Neolitsea plants were examined to enable more effective utilization of such bioactive ingredients. Of these, N. acuminatissima was found to contain the most quantity of flavonoids (ca. 0.24%leaves).     

Phenylethanoid and Phenylmethanoid Glycosides from the Leaves of Ligustrum robustum and Their Bioactivities

The phytochemical study on the leaves of Ligustrum robustum, which have been used as Ku-Ding-Cha, led to the isolation and identification of three new phenylethanoid glycosides and three new phenylmethanoid glycosides, named ligurobustosides R₁ (1b), R_2–3 (2), R₄ (3), S₁ (4b), S₂ (5), and S₃ (6), and five reported phenylethanoid glycosides (7–11). In the bioactivity test, (Z)-osmanthuside B₆ (11) displayed strong fatty acid synthase (FAS) inhibitory activity (IC₅₀: 4.55 ± 0.35 μM) as the positive control orlistat (IC₅₀: 4.46 ± 0.13 μM), while ligurobustosides R₄ (3) and S₂ (5), ligupurpuroside B (7), cis-ligupurpuroside B (8), ligurobustoside N (9), osmanthuside D (10), and (Z)-osmanthuside B₆ (11) showed stronger ABTS radical scavenging activity (IC₅₀: 2.68 ± 0.05~4.86 ± 0.06 μM) than the positive control L-(+)-ascorbic acid (IC₅₀: 10.06 ± 0.19 μM). This research provided a theoretical basis for the leaves of L. robustum as a tea with function in treating obesity and diabetes.     

New Oxygenated Lignans from Kadsura philippinensis

Seven new oxygenated lignans, kadsuphilins G–M ( 1 – 7 , resp.), were isolated by chromatographic fractionation of an AcOEt extract of the aerial part of Kadsura philippinensis including four compounds with a dibenzocyclooctadiene skeleton, two with a bicyclooctane ring system, and one of 1,4‐biphenyldimethylbutane type. The structures of the isolated compounds were elucidated through extensive spectroscopic analyses, particularly 2D‐NMR experiments (HMQC, HMBC, and NOESY). The configuration of the chiral centers and the biphenyl moiety were determined by NOESY as well as CD spectroscopy, respectively.     

Glycosides from the Leaves of Ilex latifolia

Nine new triterpenoid saponins; latifolosides I? Q and three known compounds: Kudinoside A, cis‐roseoside, and kaempferol‐3‐O‐α‐L‐rhamnopyranosyl (1–6)‐O‐β‐D‐glucopyanoside were isolated from the leaves of Ilex latifolia. Their structures were elucidated by spectroscopic and chemical methods.     

Triterpene Acids from the Leaves of Planchonella Duclitan (Blanco) Bakhuizan

From the methanolic extract of the leaves of Planchonella duclitan, 2α,3α,19α,23‐tetrahydroxy‐13,27‐cyclours‐11‐en‐28‐oic acid (1), myrianthic acid (2), 2‐hydroxyursolic acid (3), ursolic acid (4), pomolic acid (5), rotundic acid (6), and jacoumaric acid (7) were isolated, and their structures were elucidated on the basis of their spectroscopic analysis. Among them, compound 1 was a new cyclopropyl ursane‐type triterpene acid. Additionally, compounds 4 and 7 showed significant cytotoxicity toward human colorectal carcinoma cell line HT29 and human breast carcinoma cell line MCF‐7 with IC₅₀ values ranging from 5.8 ± 1.4 to 6.5 ± 1.9 μM.     

8‐(3,3‐Dimethylallyl)‐Substituted Flavonoid Glycosides from the Aerial Parts of Epimedium koreanum

Ten 8‐(3,3‐dimethylallyl)‐substituted flavonoid glycosides, including the four new flavonol glycosides 1 and 3 – 5 and the new flavanonol glycoside 2 , besides five known flavonol glycosides, were isolated from the aerial parts of Epimedium koreanum Nakai . Their structures were determined by spectroscopic methods, including UV, IR, 1D‐ and 2D‐NMR, ESI‐MSⁿ, HR‐ESI‐MS, and circular dichroism (CD) experiments.     

Flavonoid Constituents from Spiraea brahuica

Sparins A–C ( 1 – 3 , resp.), three new flavonoids, were isolated from the CHCl₃ subfraction of the EtOH extract of the whole plant of Spiraea brahuica, along with 3′,7‐di‐O‐methylquercetin ( 4 ) and luteolin 7‐β‐D ‐glucopyranoside ( 5 ), reported for the first time from this species. The structures of the new compounds were elucidated by spectroscopic techniques including MS and 2D‐NMR spectroscopy.     

Concise Synthesis and Antidiabetic Effect of Three Natural Triterpenoid Saponins Isolated from Fadogia ancylantha (Makoni tea)

The first concise synthesis of the bidesmosidic oleanolic acid saponins 1 – 3 isolated from Fadogia ancylantha (Makoni tea) have been accomplished through a ‘one‐pot sequential glycosylation’ strategy with two glycosyl 1‐(trichloroacetimidate)s as glycosyl donors. The synthesized natural products 1 – 3 were then evaluated for their inhibitory activities against α‐glucosidase, α‐amylase, and lipase. Among the assayed compounds 1 – 3 , compound 1 showed strong α‐glucosidase and α‐amylase inhibition, with IC₅₀ values of 160 and 180 μM , respectively. Moreover, compounds 2 and 3 showed strong inhibition against α‐glucosidase and lipase, with the respective IC₅₀ values of 170 and 190 μM , and 190 and 200 μM .     

Investigation of Flavonoid Glycosides from Neolitsea Sericea var. Aurata via the General Method and HPLC‐SPE‐NMR

Six flavonoid rhamnosides ( 1‐2, 4‐7 ) were separated from the water‐soluble non‐alkaloidal portion of the EtOH extract of the leaves of Neolitsea sericea var. aurata using various chromatographic techniques including Sephadex LH‐20, centrifugal partition chromatography, and RP‐18 Lobar. One additional compound ( 3 ) besides these six was identified by application of HPLC‐SPE‐NMR in a flavonoid rich fraction. The latter approach consumed only 1.5 mg of samples, theoretically equivalent to 0.2 g of dry leaves. This study demonstrates that HPLC‐SPE‐NMR has great advantage over the general methods on the aspects of manpower, research time, amounts of plant materials, and consumables in separation and characterization of natural products.     

Bioassay-Guided Isolation of New Flavonoid Glycosides from Platanus × acerifolia Leaves and Their Staphylococcus aureus Inhibitory Effects

Despite the rapid advances in drug R&D, there is still a huge need for antibacterial medications, specifically for the methicillin-resistant Staphylococcus aureus (MRSA). Inspired by the research where a viable class of MRSA inhibitors was found in the species Platanus occidentalis, a S. aureus inhibition screening-guided phytochemical reinvestigation on Platanus × acerifolia (London plane tree) leaves were performed with four flavonoid glycosides garnered, including two new compounds, quercetin-3-O-α-l-(2″-E-p-coumaroyl-3″-Z-p-coumaroyl)-rhamnopyranoside (E,Z-3′-hydroxyplatanoside, 1) and quercetin-3-O-α-l-(2″-Z-p-coumaroyl-3″-E-p-coumaroyl)-rhamnopyranoside (Z,E-3′-hydroxyplatanoside, 2). All of the isolates showed significant S. aureus ATCC 25904 inhibitory activity with MICs ranging from 4 to 64 μg/mL, suggesting the potential of discovering drug leads for the control of S. aureus from such a rich, urban landscaping plant in the Platanus genus.