Subcritical extraction of birch bark pentacyclic triterpenes

Natural pentacyclic triterpenes were extracted from birch bark with subcritical solvents. The influence of the solvent nature, temperature, and the number of extraction cycles on the efficiency of the process was studied. Using methanol at 100 °С provides the highest tri-terpene extraction rate. Bark extracts prepared using various solvents were analyzed for chemical composition and antioxidant activity.     

Two new phenylbutanoids from inner bark of Betula pendula

Two phenylbutanoids, 7-{3R-[(4-hydroxyphenyl)butyl] beta-glucopyranosid-O-6-yl} 4-O-beta-glucopyranosylvanillin and 3-beta-glucopyranosyloxy-1-(4-hydroxyphenyl)-butanone were isolated from an aqueous methanol extract of the inner bark of Betula pendula. Their structures were determined by NMR spectroscopy and mass spectrometry. The complete assignment of proton and carbon signals was achieved by 1D and 2D NMR experiments: selective 1D TOCSY, HSQC, HMBC and DQF-COSY.     

Hydroxystilbenes of the inner bark of Pinus sibirica

Summary In addition to pinostilbene and resveratrol, two new stilbene glycosides have been isolated from the phloem ofPinus sibirica R. Mayr, and their structures have been established as 3,4-dihydroxy-5-methoxy-stilbene 4--D-glycopyranoside (pinostilbenoside) and 3,4,5-trihydroxystilbene 4--D-glycopyranoside (resveratroloside).Irkutsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 677–682, November–December, 1975.     

Degradation effects in the extraction of antioxidants from birch bark using water at elevated temperature and pressure

Experiments with birch bark samples have been carried to enable a distinction between extraction and degradation effects during pressurised hot water extraction. Two samples, E80 and E180, contained birch bark extracts obtained after extraction at 80 and 180 °C for up to 45 min, respectively. Two other samples, P80 and P180, were only extracted for 5 min at the two temperatures and were thereafter filtered and hydrothermally treated at 80 and 180 °C, respectively. During the latter treatment, samples were collected at different times to assess the stability of the extracted compounds. An offline DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, as well as a high performance liquid chromatographic separation coupled to an electrochemical detector, were used to determine the antioxidant capacity of the processed samples. The results obtained with the different techniques were compared to assess the yield of the extraction and degradation processes. In addition, an online hyphenated system comprising high performance liquid chromatography coupled to diode-array; electrochemical; and tandem mass spectrometric detection (HPLC-DAD-ECD-MS/MS) was used to study the compositions of the extracts in more detail. The results for the samples processed at 80 °C showed that the extraction reached a steady-state already after 5 min, and that the extracted compounds were stable throughout the entire extraction process. Processing at 180 °C, on the other hand, gave rise to partly degraded extracts with a multitude of peaks in both the diode array and electrochemical detectors, and a higher antioxidant capacity compared to for the extracts obtained at 80 °C. It is concluded that HPLC-DAD-ECD is a more appropriate technique for the determination of antioxidants than the DPPH assay. The mass spectrometric results indicate that one of the extracted antioxidants, catechin, was isomerised to its diastereoisomers; (+)-catechin, (−)-catechin, (+)-epicatechin, and (−)-epicatechin.     

Chemical profiles of birch and alder bark by ambient mass spectrometry

Desorption atmospheric pressure photoionization (DAPPI) is an ambient mass spectrometry (MS) technique that allows the analysis of both polar and nonpolar compounds directly from the surfaces of various sample types. Here, DAPPI was used to study the chemical profiles in different parts of birch and alder tree barks. Four distinct fractions of Betula pendula (silver birch) bark were collected from three different developmental stages of the stem, after which the chemical profiles of the different tissue types were measured. Of special interest were triterpenoids, a class of important defensive substances, which are found in the bark of the silver birch. Additionally, the chemical profiles of lenticels and the surrounding surfaces in the phellem of B. pendula (silver birch), Alnus glutinosa (black alder), and Alnus incana (gray alder) were screened with DAPPI. Another ambient MS technique, laser ablation atmospheric pressure photoionization (LAAPPI), was further used for the mass spectrometry imaging of lenticels on the B. pendula phellem. All the studied birch bark fractions showed individual chemical profiles in DAPPI. The mass spectra from the young apical stem and the transition zone resembled each other more than the mature stem. Instead, the phellem was found to contain a high amount of triterpenoids in all the developmental stages of the stem. The most intense peaks in the DAPPI mass spectra of the birch bark fractions were those of betulin and lupeol. Betulinic and betulonic acid peaks were intense as well, and these compounds were detected especially in the lenticels of the tree samples.

Graphical abstract

     

Sesquiterpenes and Flavonoids from Serratula Strangulata

Phytochemistry investigation of the whole plants of Serratula strangulata has led to the isolation of two sesquiterpenes, six flavonoids, and two isoflavonoids. Among these, a sesquiterpene and two flavonoids are new compounds. The structures of these new compounds were elucidated by spectroscopic methods and 2D NMR techniques.     

Sesquiterpenes from the roots of Cichorium endivia

Twelve new sesquiterpene and sesquiterpene glycosides were obtained along with eleven known compounds from the roots of Cichorium endivia (Compositae). The compounds were identified as guaianolide, germacrenolide and elemanolide, based on spectroscopic methods and chemical evidence.     

Sesquiterpenes from the Roots of Ligularia duciformis

Two new sesquiterpenes named liguducin-A ( 1 ) and -B ( 4 ) were isolated from a Chinese medicinal plant, the dried roots of Ligularia duciformis, together with four known sesquiterpenes, 4α, 10β-dihydroxy-1β,5α-H-guai-6-ene ( 2 ), 4α-hydroxy-1β,5α,11α-H-guai-9-en-12,8α-olide ( 3 ), 1β-hydroxyeudesm-4,11-dien-3-one ( 5 ) and 1β,6α-dihydroxyeudesm-4(15)-ene ( 6 ). On the basis of the spectral evidence, their structures were determined.     

Vibrational spectroscopy of betulinic acid HIV inhibitor and of its birch bark natural source

Raman and IR spectra of betulinic acid (BA) (3beta-hydroxy-20(19) lupaen-28 oic acid) and of the natural birch bark have been successfully recorded and discussed. A high selectivity of the Raman technique was remarked for evidencing the betulin in the birch bark. Surface enhanced Raman spectrum (SERS) of BA on colloidal silver has been obtained. The presence and shifting of the symmetric stretching mode of the COO group in the SERS spectrum suggests a chemisorption of the steroid structure on the metallic particles.     

Novel Sesquiterpenes from the Fungus Lactarius piperatus

Four novel sesquiterpenes, namely 7α,8β,13‐trihydroxy‐5,13‐marasmanolide ( 2 ), isoplorantinone ( 5 ), 4,8,14‐trihydroxyilludala‐2,6,8‐triene ( 6 ), and 8‐hydroxy‐8,9‐secolactara‐1,6‐dien‐5,13‐olide ( 10 ), together with six known ones, 7α,8β‐dihydroxy‐5,13‐marasmanolide ( 1) , 7α,8α‐dihydroxy‐5,13‐marasmanolide ( 3 ), isolactarorufin ( 4 ), blennin A ( 7 ), blennin D ( 8 ), and lactarorufin ( 9 ), were isolated from the ethanolic extract of Lactarius piperatus. The structures of these sesquiterpenes, representing diversified structural types, were determined mainly by spectroscopic methods, especially 2D‐NMR techniques. The structure of 6 was further confirmed by a single‐crystal X‐ray‐diffraction determination.     

New and Bioactive Sesquiterpenes from Schisandra sphenanthera

Three new sesquiterpenes, schisansphenins A ( 1 ) and B ( 2 ) and (?)‐γ‐cuparenol ( 3 ), were isolated from an acetone extract of the fruits of Schisandra sphenanthera. The known compound 4 was isolated for the frist time from a natural source. The structures of the isolated compounds were elucidated through extensive spectroscopic analyses, particularly 2D‐NMR experiments (¹H,¹H‐COSY, HMQC, HMBC, and NOESY). A plausible biogenetic pathway for schisansphenin B ( 2 ) is proposed. Compounds 2 and 3 significantly reduced activation of NF‐AT and NF‐κB in the luciferase‐reporter assay.     

Sesquiterpenes from the fruits of Illicium Simonsii maxim

Abstract

A new allo-cedrane sesquiterpene glycoside (1) and nine known compounds (2–10) were isolated from the ethanol extract of the fruit of Illicium simonii Maxim. Their structures were elucidated by spectroscopic methods, including 1D-, 2D-NMR, and HRESIMS. The absolute configuration of compound 1 was confirmed by CD experiments. Among them, compounds 1, 4, 5, and 7 displayed moderate anti-inflammatory activities by use of an in vitro bioassay.