Six 2′-hydroxyflavonols from Gutierrezia microcephala

Six 2′-hydroxyflavonols were isolated from Gutierrezia microcephala, including four new compounds, 5,7,2′-trihydroxy-3,6,4′,5′-tetramethoxyflavone, 5,7,2′-trihydroxy-3,6,8,4′,5′-pentamethoxyflavone, 5,2′-dihydroxy-3,6,7,8,4′,5′-hexamethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,8,5′-trimethxoyflavone and two known compounds, 5,7,2′,5′-tetrahydroxy-3,6,8,4′-tetramethoxyflavone and 5,7,2′,4′-tetrahydroxy-3,6,8,5′-tetramethoxyflavone.     

Two polymethoxylated flavonoids with antioxidant activities and a rearranged clerodane diterpenoid from the leaf exudates of Microglossa pyrifolia

Three novel compounds; two polymethoxylated flavonoids, 5,7,4′-trihydroxy-3,8,3′,5′-tetramethoxyflavone (1), 5,7,3′-trihydroxy-3,8,4′,5′-trimethoxyflavone (2), and a clerodane diterpenoid; 8-acetoxyisochiliolide lactone (3) were characterized from the leaf exudates of Microglossa pyrifolia. In addition, three known polymethoxylated flavonoids including; 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone (4), 5,3′4′-trihydroxy-3,7,8-trimethoxyflavone (5), 5,3′4′-trihydroxy-7-methoxyflavanone (6) and a clerodane diterpenoid; 7,8-epoxyisocholiolide lactone (7) were identified. Their structures were determined on the basis of spectroscopic evidence. All the compounds did not exhibit antiplasmodial and antimicrobial activities at 47.6 μg/mL and were not cytotoxic at 5 μg/mL. Compound 6 exhibited modest antileishmanial activity with IC₅₀ value of 13.13 μg/mL with 5 and 7 showing activities with IC₅₀ values of 31.13 and 38.00 μg/mL, respectively, therefore inactive. The flavonoids (quercetin derivatives, 4 and 5) showed similar antioxidant activities, using 2,2-diphenylpicrylhydrazyl (DPPH) assay, with IC₅₀ values of 6.2 ± 0.3 μg/mL for 4 (17.3 μM) and 5 (17.8 μM) respectively. These activities were comparable to that of the standard quercetin (IC₅₀ value of 6.0 ± 0.2 μg/mL (19.9 μM)), irrespective of methylation of the characteristic hydroxyl groups expected to be responsible for activity and additional substitution at C-8 in ring A of the flavonoid ring. These studies revealed that the presence of an hydroxyl group at C-4′ positions and oxygenation at C-3 in flavone skeleton, appears to be necessary for good antioxidant activities as encountered in compounds 1, 4 and 5. Substantial reduction in antioxidant activity was shown by methoxylation of the 4′-OH as observed in compound 2 with an IC₅₀ value of 8.79 ± 0.3 μg/mL (24.4 μM).     

Flavonoids of Gardenia cramerii and G. fosbergii bud exudates

From the bud exudates of Gardenia cramerii and G. fosbergii, two species endemic to Sri Lanka, a new flavonoid with an unusual B-ring oxidation pattern, 5,5′-dihydroxy-6,7,2′,3′-tetramethoxyflavone, was characterized. Two other rare flavonoids, 5,3′,5′-trihydroxy-3,6,7,4′-tetramethoxyflavone and 5-hydroxy-6,7,3′,4′,5′-pentamethoxyflavone were also isolated from both Gardenia species.     

Phytochemical analysis of the labdanum-poor Cistus creticus subsp. eriocephalus (Viv.) Greuter et Burdet growing in central Italy

Phenolic constituents and essential oil from the aerial parts of Cistus creticus subsp. eriocephalus (Viv.) Greuter et Burdet growing in central Italy were analysed by HPLC-MSⁿ and GC–MS, respectively. Furthermore, six constituents were isolated by semipreparative HPLC from the methanol extract and their structures were determined on the basis of 1D and 2D NMR measurements as well as MS spectra. Isolated compounds were one new natural product, i.e. the shikimic acid ester 3,5-diihydroxy-4-(O-β-d-glucopyranosyl)-cyclohex-1-en-1-(O-β-d-glucopyranosyl)-ester (27), and six flavonoid glycosides, namely quercetin-3-O-β-D glucopyranoside (16), quercetin-3-O-rhamnoside (17), tricetin-4′-O-β-D glucopyranoside (24), tricetin-4′-O-β-D rutinoside (21), 3′-methoxy-quercetin-3-O-(3-β-Dglucopyranosyl-2-rhamnopyranosil-4-glucopyranosyl-2-rhamnopyranosil)-glucoside (25) and 3′,4′dimethoxyquercetin-3-O-rhamnopyranoside (26). GC–MS analysis of the essential oil highlighted the occurrence of aliphatic compounds, mainly fatty acids, whereas labdane-type compounds were very scant. Our results showed that C. creticus subsp. eriocephalus has a different chemical profile with respect to the other subspecies due to the lack of labdane derivatives. On the other hand, this subspecies contains several phenolic constituents like ellagitannins, gallotannins and flavonoids, some of which can be of chemotaxonomic value.     

A New Bipyrrole and Some Phenolic Constituents in Prunes (Prunus domestica L.) and Their Oxygen Radical Absorbance Capacity (ORAC)

Isolation and structural elucidation of prune constituents were performed and total 10 compounds were determined by NMR and MS analyses. A novel compound was identified to be 2-(5-hydroxymethyl-2′,5′-dioxo-2′,3′,4′,5′-tetrahydro-1′H-1,3′-bipyrrole)carbaldehyde, and 7 phenolic compounds were isolated from prunes for the first time. In addition, antioxidant activity of them was evaluated on the basis of the oxygen radical absorbance capacity (ORAC).     

Chemical constituents from the leaves of Cinnamomum parthenoxylon (Jack) Meisn. (Lauraceae)

Phytochemical investigation of the ethanolic extract from the leaves of Cinnamomum parthenoxylon (Jack) Meisn. led to the isolation of (3R, 4R, 3′R, 4′R)-6,6′-dimethoxy-3, 4, 3′, 4′-tetrahydro-2H, 2′H-[3, 3′]bichromenyl-4, 4′-diol (1), 4-hydroxybenzaldehyde (2), 1,2,4-trihydroxybenzene (3), kaempferol-3-O-α-l-rhamnoside (4), herbacetin (5), quercetin-3-O-α-l-rhamnoside (6), daucosterol (7), and β-sitosterol (8). The structures were established by extensive analysis of their MS and NMR spectroscopic data and comparison with literature data. In the present research, all of the isolated compounds 1–8 are reported for the first time in the species C. parthenoxylon. Compounds 1–6 were firstly isolated from genus Cinnamomum. Compounds 1, 3, 5 and 6 have not been reported from any species in Lauraceae family. The chemotaxonomic significance of the isolated compounds is discussed.     

Secondary metabolites of Sophora mollis subsp. griffithii (Stocks) Ali

Two new compounds, (+)-3,5,7-trihydroxy-3-[3′-hydroxy-2′,4′-dimethoxy-5-(3-methyl-2-butenyl)]-phenyl-(3R)-4H-1-benzopyran-4-one (1) and (?)-3-hydroxy-8,9-methylenedioxy-(6aR,11aS)-pterocarpan (2), were isolated from the methanolic extract of Sophora mollis subsp. griffithii. Two known compounds, β-sitosterol (3) and 19βH-lupeol-methyl-ether (4), were also obtained for the first time from this plant. The structures of 1–4 were identified through their spectroscopic data. CD Spectroscopy was also utilized for the structure elucidation of compounds 1 and 2. Compounds 1, 3 and 4 were studied for their effects on immune cells and only 1 was found to be substantially active.     

Myricetin and quercetin methyl ethers from Haplopappus integerrimus var. Punctatus

Nine flavonoids including two new myricetin derivatives, myricetin 3′,4′-dimethyl ether and myricetin 3,3′, 4′-trimethyl ether, were obtained from Haplopappus integerrimus var. punctatus. The known compounds are quercetin 7,3′-dimethyl ether, querectin 3,3′-dimethyl ether, isorhamnetin, quercetin 3,7-dimethyl ether, quercetin 3-methyl ether, quercetin and quercetin 3-β-d-glucoside.     

Phytochemical and chemotaxonomic study on Ziziphus Jujuba Mill. (Rhamnaceae)

Fourteen compounds were isolated from fruits of Ziziphus jujuba Mill., including two flavonoids (1–2), one phenolic glycosides (3), one lignan (4), four phenols (5–8), three alkaloid (9–10, 14), three sesquiterpenoid (11–13). The structures of all the compounds were established by the NMR techniques, as well as by comparison with previously reported data in literature. Compounds 2″-glucosyl-8-C-glucosyl-4′-O-methylapigenin (1), 3′, 4′, 5′-trimethoxycinnamyl alcohol (5), 2-{4-[(1E)-3-Hydroxyprop-1-en-1-yl]-2, 6-dimethoxy-phenoxy}propane-1, 3-diol (6), 1-(4-Hydroxyphenyl)ethane-1, 2-diol (8), (1S, 3S)-1-Methyl-l, 2, 3, 4-tetrahydro-β-carboline-3-carboxylic acid (9), (1R, 3S)-1-Methyl-l, 2, 3, 4-tetrahydro-β-carboline-3-carboxylic acid (10), grasshopper ketone (12), methyl (3R, 5R)-5-methoxy-3-phenylisoxazolidine-5-carboxylate (14) were firstly reported from the genus Ziziphus and the family Rhamnaceae. Furthermore, the chemotaxonomic significance of the isolates was discussed.     

Synthesis and antimicrobial activities of halogenated bis(hydroxyphenyl)methanes

A series of halophenols was prepared by the reaction of bis(hydroxyphenyl)methanes with effective halogenating agents such as bromine and sulfuryl chloride. One of these compounds, a biologically active halophenol—2,2′,3,3′-tetrabromo-4,4′,5,5′-tetrahydroxydiphenylmethane (1)—frequently isolated from red algae, was synthesized for the first time. Other halophenols included several novel compounds, together with known derivatives that were synthesized from the phenolic intermediates, bis(3,4-dihydroxyphenyl)methane (5) and bis(2-hydroxyphenyl)methane (14). All of the synthesized compounds were tested for antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. The preliminary structure–activity relationship was investigated in order to determine the essential structural requirements for their antimicrobial activity. Of all these halophenols, 2,2′,3,3′,6-pentabromo-4,4′,5,5′-tetrahydroxydiphenylmethane (8) was found to be the most active against Candida albicans, Aspergillus fumigatus, Trichophyton rubrum, and Trichophyton mentagrophytes while 3,3′,5,5′-tetrachloro-2,2′-dihydroxydiphenylmethane (18) exerted a powerful antibacterial effect against Staphylococcus aureus, Bacillus subtilis, Micrococcus luteus, Proteus vulgaris, and Salmonella typhimurium.     

Flavonoids from Artemisia ludoviciana var. ludoviciana

Nineteen flavonoids were isolated from Artemisia ludoviciana var. ludoviciana, including a new 2′- hydroxy- 6-methoxyflavone, 5,7,2′,4′-tetrahydroxy-6,5′-dimethoxyflavone. The known compounds include quercetagetin 3,6,3′,4′-tetramethyl ether, eupatilin, 5,7-dihydroxy-3,6,8,4′-tetramethoxyflavone, luteolin 3′,4′-dimethyl ether, jaceosidin, 5,7,4′-trihydroxy-3,6-dimethoxyflavone, tricin, hispidulin, chrysoeriol, kaempferol 3-methyl ether, apigenin, axillarin, eupafolin, selagin and luteolin together with three flavones which were previously isolated for the first time from Artemisia frigida: 5,7,4′-trihydroxy-6, 3′,5′-trimethoxyflavone, 5,7,3′-trihydroxy-6,4′,5′-trimethoxyflavone and 5,7,3′,4′-tetrahydroxy-6,5′- dimethoxyflavone.     

Methoxyspheroidene and methoxyspheroidenone,two carotenoids from Rhodopseudomonas spheroides

Two new carotenoids isolated from Rhodopseudomonas spheroides (Rhodospirillaceae) have been identified as methoxyspheroidene (1,1′-dimethoxy-3,4-didehydro-1,2,1′,2′,7$\text{,}\text{?}$8′-hexahydro-ψ,ψ-carotene) obtained from anaerobic cultures and methoxyspheroidenone (1,1′-dimethoxy-3,4-didehydro-1,2,1′,2′,7′,8′-hexahydro-ψ,ψ-caroten-2-one) recovered from aerobic cultures.     

Two new antioxidant flavones from the twigs of Eriosema robustum (Fabaceae)

Phytochemical study of the ethanol extract of the twigs of Eriosema robustum, a Cameroonian medicinal plant resulted to the isolation of two new flavones, 2′,3′,5′,5,7-pentahydroxy-3,4′-dimethoxyflavone (1) and 2′,3,5′,5,7-pentahydroxy-4′-methoxyflavone (2), along with five known compounds: 6-prenylpinocembrin (3), 1-O-heptatriacontanoyl glycerol (4), β-sitosterol (5), stigmasterol (6) and 3-O-β-d-glucopyranoside of sitosterol (7). The structure of the isolated compounds were elucidated on the basis of their NMR, UV and MS data, and by comparison with those reported in the literature. The ethanol crude extract, fractions and some isolated compounds (1–4) were evaluated for their radical scavenging capacity using 2,2-diphenyl-1-picryhydrazyl (DPPH). The crude extract, fraction II, the new compounds namely robusflavones A (1) and B (2) exhibited significant antioxidant activity.     

Octasubstituted flavones from Ageratum houstonianum

Two new highly oxygenated flavones, were isolated from aerial parts of Ageratum houstonianum. Their structures were established as 3′-hydroxy-5,6,7,8,2′,4′,5′-heptamethoxyflavone and 5,3′-dihydroxy-6,7,8,2′,4′,5′-hexamethoxyflavone on the basis of spectral data and chemical degradation. The structure of the latter compound was confirmed by X-ray analysis.     

Two new C-methylated flavonoids from Myrica gale

From the leaves of Myrica gale 2′,4′-dihydroxy-6′-methoxy-3′,5′-dimethylchalcone has been isolated. The fruits yielded 2′-hydroxy-4′,6′-dimethoxy-3′-methyldihydrochalcone. The constitutions were deduced from spectroscopic data and confirmed by synthesis.     

Flavans from Zephyranthes flava

A new optically active flavan aglucone, 7-hydroxy-3′,4′-methylenedioxyflavan, and its 7-glucoside have been isolated from the bulbs of Zephyranthes flava, collected at flowering. Additionally, two known flavans, 7,4′-dihydroxy-3′-methoxyflavan and 7-methoxy-2′-hydroxy-4′,5′-methylenedioxyflavan, have been isolated for the first time from this species. The structures of these flavans have been established by comprehensive analyses (UV, IR, ¹H NMR, ¹³C NMR, mass spectrometry, [α]_D) of the compounds and their acetates, and also by chemical correlation.     

7,2′,4′-Trihydroxy-3′-methoxyisoflavone from zollernia paraensis

Three further compounds have been isolated from Zollernia paraensis: 2,7-dihydroxy-4′-methoxy-3-phenylcoumarin, (±)-5,7-dihydroxy-2′,4′-dimethoxyisoflavanone and the new 7,2′,4′-trihydroxy-3′-methoxyisoflavone.     

Dihydrochalcones from lindera umbellata

Two dihydrochalcones, 2′,6′-dihydroxy-4′-methoxydihydrochalcone and 2,4′,6′-trihydroxydihydrochalcone have been isolated from leaves of Lindera umbellata.     

Chemotaxonomic significance of lignans from Serissa japonica (Thunb.) Thunb

Sixteen known lignans were isolated from the 95% alcohol extract of the whole plant of Serissa japonica (Thunb.) Thunb., including nine furofurans (1–9), three tetrahydrofurans (10–12) and four arylnaphthalenes (13–16). In the present report, compounds (+)-epipinoresinol (1), (+)-1-hydroxy-6-epipinoresinol 4,4″-di-O-methyl ether (3), (−)-pinoresinol (4), (+)-8-hydroxypinoresinol (6), pseuderesinol (7), (+)-1-hydroxysyringaresinol (8), (−)-(7′S,8S,8′R)-4,4′-dihydroxy-3,3′,5,5′-tetramethoxy-7′,9-epoxylignan-9′-ol-7-one (10), wikstrone (11), 7'-(+)-oxomatairesinol (12), (+)-cycloolivil (13), (+)-isolariciresinol (14), 5-methoxy-(+)-isolariciresinol (15) and cyclolignans (16) were reported from the Serissa genus for the first time, and compounds (+)-lirioresinol A (2) and (−)-lirioresinol B (5) were firstly isolated from the plant. Their structures were elucidated on the basis of extensive spectroscopic and chemical analyses. Moreover, the chemotaxonomic significance of the isolated compounds is discussed.     

Isoflavones from the roots and stems of Nicotiana Tabacum and their anti-tobacco mosaic virus activities

Two new isoflavones, 7-hydroxy-6,3′,4′,5′-tetramethoxy-isoflavone (1) and 6-hydroxy-7,3′,4′,5′-tetramethoxy-isoflavone (2), together with seven known isoflavones were isolated from the roots and stems of Nicotiana tabacum. Their structures were determined by means of HRESIMS, extensive 1D and 2D NMR spectroscopic studies and chemical evidences. The anti-tobacco mosaic virus (anti-TMV) activities of the isoflavones were also evaluated. The results reveal that compound 9 shows high anti-TMV activity, compound 2 shows moderate anti-TMV activity, and compounds 1, 3–8 show weak anti-TMV activities.