Secondary metabolites,phytochemical characterization and antioxidant activities of different extracts of Sideritis congesta P.H. Davis et Hub.-Mor.

Sideritis congesta, an endemic plant to Turkey, is extensively consumed as energizing herbal tea and used as a remedy in folk medicine. This study was designed to comparatively evaluate the phytochemical composition and antioxidant potentials of different extracts (methanol, infusion) and fractions (chloroform, ethyl acetate, and remaining water) of S. congesta. Antioxidant potentials of the samples were evaluated by DPPH radical scavenging, FRAP, CUPRAC, and total antioxidant capacity tests. Total phenolic, phenolic acid, and flavonoid contents were also evaluated spectrophotometrically. Moreover, presence of twenty-two phenolic metabolites were affirmed by using LC-MS/MS in MRM scan mode and then the quantification of verbascoside, martynoside, and leucoseptoside A was performed by using HPTLC densitometry. EtOAc fraction contained the highest phenolic content and the antioxidant activity, as well as the highest verbascoside and martynoside contents followed by R-H₂O fraction. Phytochemical studies on R-H₂O fraction, yielded seven compounds, including a phenylethanoid glycoside, verbascoside (1), two flavonoids, stachyspinoside (2), isoscutellarein 7-O-(6‴-O-acetyl)-β-allopyranosyl-(1 → 2)-β-glucopyranoside (3), a phenolic acid chlorogenic acid (4), an iridoid glycoside ajugoside (5), and a monoterpenoid glucoside mixture betulalbuside A (6) and 1-hydroxylinaloyl 6-O-β-D-glucopyranoside (7). The molecular structures of the isolated compounds were determined by NMR and MS experiments. This is the first phytochemical study on the polar constituent of S. congesta and the first report of the isolation of compounds 2, 6 and 7 from the genus Sideritis L.     

Chemical constituents from the rhizome of Anemone hupehensis

A phytochemical investigation on the rhizome of Anemone hupehensis resulted in the isolation of thirteen compounds, including six neolignan glycosides (1-6), two phenylpropanoid glycosides (7, 8), a phenolic glycoside (9) and four triterpenoid saponins (10-13). The structures of the isolated compounds were elucidated on the basis of spectroscopic data. This is the first report of neolignan glycoside, phenylpropanoid glycoside, and phenolic glycoside from genus Anemone. This is also the first study to report compounds 1-5 and 7-9 from family Ranunculaceae. All the compounds, except 10 were isolated from A. hupehensis for the first time. The chemotaxonomic significance of the isolated compounds was discussed.     

Coixlachryside A: A new lignan glycoside from the roots of Coix lachryma-jobi L. var. ma-yuen Stapf.

A new lignan glycoside, 1-[3,6-(4,4⿲-dihydroxy-3,3⿲-dimethoxy-δ-truxinyl)-β-fructofuranosyl]-α-glucopyranoside (1), named coixlachryside A, together with nine known simple phenolic compounds (3⿿11) were isolated from the roots of Coix lachryma-jobi var. ma-yuen using various chromatographic methods. Their chemical structures were determined based on the spectroscopic data interpretation, particularly circular dichroism (CD), 1D and 2D NMR data including HSQC and HMBC.     

Phenolic glycosides from Cucumis melo var. inodorus seeds

A new phenolic glycoside (E)-4-hydroxycinnamyl alcohol 4-O-(2′-O-β-d-apiofuranosyl)(1″ → 2′)-β-d-glucopyranoside (1) was isolated and identified from Cucumis melo seeds together with benzyl O-β-d-glucopyranoside (2), 3,29-O-dibenzoylmultiflor-8-en-3α,7β,29-triol (3) and 3-O-p-amino-benzoyl-29-O-benzoylmultiflor-8-en-3α,7β,29-triol (4). Their structures were elucidated by extensive NMR experiments including ¹H–¹H (COSY, TOCSY, ROESY) and ¹H–¹³C (HSQC and HMBC) spectroscopy and chemical evidence. The multiflorane triterpene esters were identified as new melon constituents.     

Chemical constituents from the stem bark of Acer tegmentosum

A new phenolic glycoside, 4-hydroxyphenylethyl-1-O-β-D-[6′-O-(4-hydroxybenzoyl)]-glucopyranoside (1) was isolated from the stem bark of Acer tegmentosum, along with seven known phenolic compounds (2–8). The structure of compound 1 was determined by spectral analyses, including HR-ESI-MS, 1D and 2D NMR (COSY, HMQC and HMBC) experiments. Compounds 3 and 4 were found in the family Aceraceae for the first time.     

Investigation on the flavonoid composition of Aconitum angustifolium Bernh. flowers and leaves

A new flavonol glycoside, kaempferol 7-O-(6-E-p-coumaroyl)-β-d-glucopyranosyl-(1 → 3)-α-l-rhamnopyranoside 3-O-β-d-galactopyranoside (1), together with other five known compounds (2–6), were identified from the flowers and leaves of Aconitum angustifolium Bernh. Their chemical structures were elucidated by extensive NMR spectral studies, as well as by ESI-MS analysis.     

Preparations of 2-epi-fortimicins A from 2-epi-fortimicin B by intramolecular base-catalyzed 2-O-acylation of 1,2′,6′-tri-N-benzyloxycarbonyl-2-epi-fortimicin B

Preparations of 2-epi-fortimicin A (4) from 2-epi-fortimicin B (3) are described. In contrast to the previously reported, selective 4-N-acylation of 1,2′,6′-tri-N-benzyloxycarbonylfortimicin B (8) with N-(N-benzyloxycarbonylglycyloxy)succinimide, 1,2′,6′-tri-N-benzyloxycarbonyl-2-epi-fortimicin B (5) underwent predominant 2-O,4-N-diacylation under similar conditions. Proof of the structure of the diacylated product is presented, with evidence that the diacylated product is formed by initial intramolecular, base-catalyzed 2-O-acylation. The in vitro antibacterial activities of 2-epi-fortimicin A (4), 2-O-glycyl-2-epi-fortimicin A (11), 1-N-glycyl-2-epi-fortimicin A (12), and 5-deoxy-2-epi-fortimicin A (13) are reported.     

Isolation of phenolic constituents and characterization of antioxidant markers from sunflower (Helianthus annuus) seed extract

A new compound, benzyl alcohol β-d-apiofuranosyl-(1→6)-β-d-(4-O-caffeoyl) glucopyranoside (1), was isolated from the seed of sunflower (Helianthus annuus), together with eight known phenolic compounds: caffeic acid (2), methyl caffeoate (3), chlorogenic acid (4), 4-O-caffeoylquinic acid (5), 3-O-caffeoylquinic acid (6), methyl chlorogenate (7), 3,5-di-O-caffeoylquinic acid (8), and eriodictyol 5-O-β-d-glucoside (9). Their structures were elucidated on the basis of spectroscopic methods and chemical evidence. The antioxidative effect of the phenolic constituents from the sunflower seeds was also evaluated based on the oxygen-radical absorbance capacity (ORAC), and the fraction containing caffeic acid derivatives showed a high antioxidant potency.     

Tyrosinase inhibitory activity of three new glycosides from Breynia fruticosa

Two new flavanone glycoside derivatives and one new sulfur-containing spiroacetal glycoside, (2R, 3R)-3-acetyl-7-methoxy-(−)-epicatechin 5-O-(6-isobutanoyl)-β-d-glucopyranoside (1), (2R, 3R)-3-acetyl-7-methoxy-(−)-epicatechin 5-O-[6-(2-methylbutanoyl)]-β-d-glucopyranoside (2) and 4-[(carboxymethyl)thio]-5′-hydroxy-phyllaemblic acid O-β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranoside ester (3), along with twelve known flavonoids and one known sulfur-containing spiroacetal glycoside, were isolated from Breynia fruticosa. Their structures were elucidated by the use of extensive spectroscopic methods (UV, IR, HR-ESI-MS, 1D and 2D NMR, and CD). The in vitro inhibition of tyrosinase activity by all of these compounds was also evaluated, and we concluded that the flavanol-containing 5-O- and 7-O-sugar moieties possessed more potent effects than the other compounds examined herein.     

Phenolic compounds from the leaves and stem bark of Pseudospondias microcarpa (A. Rich.) Engl. (Anacardiaceae)

Phytochemical study of the leaves and the stem bark of Pseudospondias microcarpa (A. Rich.) Engl. afforded eight phenolic compounds: scopoletin (1), ferulic acid (2), isovitexin (3), rhoifolin (4), quercetin 3-O-α-L-rhamnopyranoside (5), justicialoside A (6), granduloside A (7) and pithecellobiumol B (8). The structures of the isolated compounds were elucidated by spectroscopic means including 1D and 2D NMR and MS, and by comparison with previously reported data. This is the first report on the isolation of these compounds from the genus Pseudospondias. The chemotaxonomic significance of the isolated compounds within the family Anacardiaceae is discussed.     

A new semiterpenoid glycoside and a new benzofuran derivative glycoside from the roots of Heracleum dissectum

A new semiterpenoid glycoside, 3-methylbutan-1, 3-diol-1-O-β-d-glucopyranoside (1) and a new benzofuran derivative glycoside, 6-carboxylethyl-benzofuran-5-O-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranoside (2), together with seven known compounds (3-9) were isolated from the roots of Heracleum dissectum Ledeb. Their structures were elucidated on the basis of physicochemical properties and the detailed interpretation of various spectroscopic data. All the isolated compounds were screened for anti-inflammatory activity in vitro. And the result showed that compound 2 exhibited significantly inhibitory activity on nitric oxide production in RAW264.7 cells, which IC₅₀ value was equivalent to that of the positive control indomethacin.     

Two new glycosides from the whole plant of Anemone rivularis var. flore-minore

Phytochemical investigation on the whole plant of Anemone rivularis var. flore-minore led to the isolation of a new labdane-type diterpene glycoside (1) and a new trihydroxyfuranoid lignanoid glycoside (2), together with three known triterpene and triterpenoid glycosides (3–5). The structures of the two new compounds were elucidated as β-d-glucopyranosyl (13S)-13-hydroxy-7-oxo-labda-8,14-diene-18-oate (1) and (7S,7′R,8R,8′S)-7′-butoxy-7,9′-epoxy-4,4′,9-trihydroxy-3,3′-dimethoxylignane 9-O-β-d-glucopyranoside (2), on the basis of extensive spectral analysis and chemical evidence. Compound 1 is characterized by a glucose (Glc) esterified C-18 carboxyl group, which is a rarely encountered labdane-type diterpene glycoside in nature. The two new compounds (1 and 2) reported here are the first examples of diterpene glycoside and lignanoid glycoside found in the genus Anemone, and the known triterpene and triterpenoid glycosides (3–5) are identified for the first time from the title plant.     

Three new glycosides from the whole plant of Clematis lasiandra Maxim and their cytotoxicity

Phytochemical investigation on the whole plant of Clematis lasiandra Maxim led to the isolation of two new phenolic glycosides (1 and 2), one new lignanoid glycoside (3), together with three known lignanoid glycosides (4–6). The structures of the new compounds were elucidated as 4-O-β-d-galactopyranosyl-ethyl-E-caffeate (1), 4-O-β-d-galactopyranosyl-3-hydroxyl-phenylethene (2) and (8R)-3,3′-dimethoxy-4,4′,9,9′-tetrahydroxy-5′,8-lignan 3′-O-β-d-glucopyranoside (3), on the basis of extensive spectral analysis and chemical evidence. The characteristic of the polymerized C-5′–C-8 type lignanoid aglycone in glycoside 3 was found from genus Clematis for the first time. Compounds 1–6 were evaluated for their cytotoxicity against human tumor cell lines HL-60, Hep-G2 and SGC-7901, the new glycosides 1 and 2 showed significant cytotoxicity against those three tumor cell lines with IC₅₀ in the range from 9.73 to 22.31 μM, while lignanoid glycosides 3–6 showed weak cytotoxicity to those test cell lines with IC₅₀ value more than 52.71 μM.     

Flavonoids and phenolic acids from the aerial parts of Alyssum alyssoides L. (Brassicaceae)

Two phenolic acids (1 and 2) and seven flavonoids (3–9) were isolated from the aerial parts of Alyssum alyssoides (Brassicaceae). All these compounds (1–9) were isolated from this particular species for the first time. Their structures were identified, on the basis of MS and NMR spectra as: p-hydroxy-benzoic acid (1), 3-methoxy-4-hydroxybenzoic acid (vanillic acid) (2), kaempferol 3-O-β-D-glucopyranoside (astragalin) (3), kaempferol 3-O-(6″-α-L-rhamnopyranosyl)-β-D-glucopyranoside (nicotiflorin) (4), quercetin 3-O-β-D-glucopyranoside (isoquercetin) (5), quercetin 3-O-β-D-galactopyranoside (hyperoside) (6), isorhamnetin 3-O-β-D-glucopyranoside (7), isorhamnetin 3-O-β-D-galactopyranoside (8) and isorhamnetin 3-O-(6″-α-L-rhamnopyranosyl)-β-D-glucopyranoside (narcissin) (9). The chemotaxonomic significance of these compounds was summarized.     

Corrigendum to “A new phenylethyl glycoside and a new dibenzocyclooctadiene lignan from the leaves of Kadsura coccinea (Lem.) A. C. Smith” [Phytochem. Lett. 45 (2021) 57–62]

A new phenylethyl glycoside (1), (S)-1-phenylethyl-6-α-L-arabinopyranosyl-β-D-glucopyranoside), and a new dibenzocyclooctadiene lignan (7), Kasuracin A, together with seven known compounds, were isolated and identified from the leaves of Kadsura coccinea. Their structures were determined by analysis of multinuclear and multidimensional nuclear magnetic resonance (NMR), circular dichroism (CD), mass spectrometry, hydrolysis analysis, or comparison to those reported in the literature. Then, all the isolates 1‒9 were evaluated for their inhibitory eff ;ects against nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Among them, compounds 2 and 3 were isolated for the first time from this plant and compounds 3, 7, 8, and 9 significantly inhibited NO production with IC₅₀ values of 36.4, 10.2, 12.3, and 21.7 μM, respectively.     

New ellagitannin and galloyl esters of phenolic glycosides from sapwood of Quercus mongolica var. crispula (Japanese oak)

Two novel glycosides, 4,5-dimethoxy-3-hydroxyphenol 1-O-β-(6′-O-galloyl)-glucopyranoside (1) and (+)-2α-O-galloyl lyoniresinol 3α-O-β-d-xylopyranoside (2), as well as a novel ellagitannin named epiquisqualin B (3), were isolated from sapwood of Quercus mongolica var. crispula along with 19 known phenolic compounds. The structures of the novel compounds were elucidated on the basis of chemical and spectroscopic investigation. Compound 2 is the first example of a lignan galloyl ester, and 3 is the oxidation product of vescalagin, which is the major ellagitannin of this plant.     

N-Acetyldopamine derivatives from Periostracum Cicadae

Five new N-acetyldopamine (NADA) derivatives (1–5) and one known NADA quinone methide (6) were isolated from Periostracum Cicadae (the cast-off shell of the cicada Cryptotympana pustulata Fabricius), which is known as chantui in China and is used in traditional Chinese medicine to treat soreness of the throat, hoarseness, itching, and spasms. By combined analysis of one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, CD spectra, and chemical evidence, the structures of the isolated compounds were established as (R)-N-(2-(3,4-dihydroxyphenyl)-1-ethoxy-2-oxoethyl)acetamide (1), (1R,2R)-N-(1,2-diethoxy-2-(3,4-dihydroxyphenyl)-ethyl)acetamide (2), (R)-N-(1-acetamido-2-ethoxy-2-(3,4-dihydroxyphenyl)-ethyl)acetamide (3), (1R,2R)-N-(2-(3,4-dihydroxyphenyl)-2-ethoxy-1-methoxyethyl)acetamide (4), (1S,2S)-N-(2-(3,4-dihydroxyphenyl)-2-ethoxy-1-methoxyethyl)acetamide (5), and (R)-N-(2-(3,4-dihydroxyphenyl)-2-methoxyethyl)acetamide (6).     

Phenylpropanoid amides from the roots of Solanum melongena L. (Solanaceae)

Phytochemical investigation of the roots of Solanum melongena L. led to the isolation of 16 phenylpropanoid amides (1–16). Their structures were identified by analysis of spectroscopic data and comparison with those reported in the literature. This is the first report of the natural occurrence of N-trans-sinapoyloctopamine (9) and N-trans-caffeoyloctopamine (10). N-trans-feruloylnoradrenline (12) and N-cis-feruloylnoradrenline (16) were isolated from the genus Solanum for the first time. Four compounds including 3-(4-hydroxyphenyl)-N-[2-(4-hydroxyphenyl)-2-methoxyethyl] acrylamide (5), 3-(4-hydroxy-3-methoxyphenyl)-N-[2-(4-hydroxyphenyl)-2-methoxyethyl] acrylamide (6), N-trans-p-coumaroylnoradrenline (11), and N-cis-p-coumaroyloctopamine (15) were firstly reported from S. melongena. The chemotaxonomic significance of these compounds was summarized.     

N-Substituted acetamide glycosides from the stems of Ephedra sinica

Five new N-mono-/bis-substituted acetamide glycosides, N-{4-O-[3-O-(4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (1), N-methyl-N-{4-O-[3-O-(4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (2), N-methyl-N-{4-O-[3-O-(6-O-benzoyl-4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (3), N-methyl-N-{4-O-[3-O-(6-O-benzoyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (4), and N-methyl-N-{4-O-[3-O-(6-O-trans-cinnamoyl-4-O-α-l-rhamnopyranosyl-β-d-glucopyranosyl)-α-l-rhamnopyranosyl]-phenethyl}-acetamide (5), along with one known acetamide derivative, N-methyl-N-(4-hydroxyphenethyl)-acetamide, the shared aglycone of 2–5, were isolated from the ethanol extract of the stems of Ephedra sinica. The structures of these new compounds were elucidated on the basis of extensive spectroscopic examination, mainly including multiple 1D and 2D NMR and HRESIMS examinations, and qualitative chemical tests. All N,N-bissubstituted acetamide glycosides were found to show the obvious rotamerism, as in the case of the isolated known N-methyl-N-(4-hydroxyphenethyl)-acetamide, under the experimental NMR conditions, with the ratios of integrated intensities between anti- and syn-rotamers always being found to be about 4 to 3.     

Iridoids,monoterpenoid glucoindole alkaloids and flavonoids from Vinca major

A new secoiridoid glucoside, vinmajoroside (1), was isolated from the leaves of Vinca major L. along with 11 known compounds belonging to the secoiridoid ((7α)-7-O-methylmorroniside, 2), iridoid (loganin, loganic acid and 7-O-p-coumaroylloganin), monoterpenoid glucoindole alkaloid (5 (S)-5-carboxyvincoside and strictosamide), flavonoid (rutin, kaempferol 3-O-rutinoside and robinin), lignan (syringaresinol 4-O-β-glucopyranoside) and phenolic acid (chlorogenic acid) groups. The structure elucidation of the isolates was accomplished by extensive 1D and 2D-NMR experiments as well as ESI-MS. Secoiridoids and lignan were encountered for the first time in the genus Vinca.